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Chlamydia pneumoniae and Coronary Artery Disease: The Antibiotic Trials

      Parallel with the mounting evidence that atherosclerosis has a major inflammatory component, provoking agents that may initiate and drive this process have been sought. Infectious agents such as Chlamydia pneumoniae have been alleged to be activators of inflammation that may contribute to atherosclerosis and thus coronary artery disease (CAD) and its associated complications. A logical extension of this theory is whether treating C pneumoniae infection with antibiotics and/or modulating inflammatory processes can affect CAD and its sequelae. This article discusses the potential role of C pneumoniae in atherosclerosis, its detection, and the rationale for antibiotics. Additionally, it summarizes the current randomized clinical trials of antichlamydial antibiotics in patients with CAD and draws conclusions based on the results.
      ACADEMIC (Azithromycin in Coronary Artery Disease: Elimination of Myocardial Infection with Chlamydia), ACES (Azithromycin and Coronary Events Study), AZACS (Azithromycin in Acute Coronary Syndromes), CAD (coronary artery disease), CI (confidence interval), CLARIFY (Clarithromycin in Acute Coronary Syndrome patients in Finland), MI (myocardial infarction), PCR (polymerase chain reaction), PROVE IT (Pravastatin or Atorvastatin Evaluation and Infection Therapy), ROXIS (Randomized Trial of Roxithromycin in Non-Q-Wave Coronary Syndromes), STAMINA (South Thames Trial of Antibiotics in Myocardial Infarction and Unstable Angina), WIZARD (Weekly Intervention with Zithromax for Atherosclerosis and its Related Disorders)
      Coronary artery disease (CAD) is a major cause of morbidity and mortality in humans worldwide. By the year 2020, CAD is predicted to be the leading cause of death and disability in the world.
      • Gaziano JM
      Global burden of cardiovascular disease.
      Recently, further understanding at the molecular level revealed that atherosclerosis is an inflammatory disease; thus, an infection being linked to CAD is biologically plausible.
      • Libby P
      Current concepts of the pathogenesis of the acute coronary syndromes.
      A focus on the triggers of the earliest changes of atherosclerosis (endothelial dysfunction) and inflammation that precede atherosclerotic lesions has centered on several microorganisms.
      The infectious hypothesis of atherosclerosis was postulated during the latter part of the 19th century: Gilbert and Leon described fatty sclerotic change in an arterial wall of a rabbit after slight mechanical injury coupled with injection of pathogenic bacteria.
      • Nieto FJ
      Infections and atherosclerosis: new clues from an old hypothesis?.
      Chlamydia pneumoniae, a gramnegative bacterium that causes upper respiratory tract infection, is associated with CAD. The association of C pneumoniae with CAD was first noted in 1988 by Saikku et al
      • Saikku P
      • Leinonen M
      • Mattila K
      • et al.
      Serological evidence of an association of a novel Chlamydia, TWAR, with chronic coronary heart disease and acute myocardial infarction.
      in Finland. Since then, a large body of research has shown that C pneumoniae is associated seroepidemiologically with CAD, although not all studies or cohorts have found a significant relationship after correcting for con-founders. Additionally, direct pathological evidence revealing the presence of C pneumoniae in atherosclerotic plaques and the ability to culture viable C pneumoniae from plaque have added credence to this hypothesis. However, the issue of the “innocent bystander” has not been clarified. Moreover, animal models (rabbits, chickens, and mice) confirm C pneumoniae-induced atherogenesis.
      • Fong IW
      • Chiu B
      • Viira E
      • et al.
      Can an antibiotic (macrolide) prevent Chlamydia pneumoniae-induced atherosclerosis in a rabbit model?.
      • Fong IW
      • Chiu B
      • Viira E
      • Jang D
      • Mahony JB
      De novo induction of atherosclerosis by Chlamydia pneumoniae in a rabbit model.
      • Muhlestein JB
      • Anderson JL
      • Hammond EH
      • et al.
      Infection with Chlamydia pneumoniae accelerates the development of atherosclerosis and treatment with azithromycin prevents it in a rabbit model.
      Although C pneumoniae is considered the pathogen most likely to have an etiologic role in CAD, this causality in humans is not fully evident. Nonetheless, large randomized controlled trials are analyzing the effect of treating patients with CAD and its associated complications with antibiotics that have activity against C pneumoniae.

      METHODS

      The English-language scientific literature was reviewed primarily by searching MEDLINE and EMBASE databases for the period 1976 through July 2002. Keywords used in the search included chlamydia, pneumoniae, coronary, artery, disease, atherosclerosis, antibiotics, and inflammation. The reference lists of articles found through these searches were also reviewed for relevant articles. In addition, links on Web sites containing published articles were searched for relevant information.

      ATHEROSCLEROSIS, INFLAMMATION, AND INFECTION

      The body's inflammatory response plays an important role in the progression of atherosclerosis and vulnerable plaque.
      • Ross R
      Atherosclerosis—an inflammatory disease.
      • Keaney Jr, JF
      • Vita JA
      The value of inflammation for predicting unstable angina [editorial].
      One theory is that, in certain genetically susceptible people, infection with common organisms such as C pneumoniae may lead to a localized infection and a chronic inflammatory reaction that may accelerate atherosclerosis.
      • Mehta JL
      • Saldeen TG
      • Rand K
      Interactive role of infection, inflammation and traditional risk factors in atherosclerosis and coronary artery disease.
      Specifically, how can C pneumoniae affect the biology of atherosclerotic plaque? Four theories are described subsequently.
      • 1.
        Infection with C pneumoniae may contribute to endothelial dysfunction, which is believed to underlie and precede the pathological atherosclerotic process.
        • Libby P
        Changing concepts of atherogenesis.
        Inoculation of apolipoprotein E knockout mice (which develop atherosclerotic lesions spontaneously) with C pneumoniae results in endothelial dysfunction via the nitric oxide pathway.
        • Liuba P
        • Karnani P
        • Pesonen E
        • et al.
        Endothelial dysfunction after repeated Chlamydia pneumoniae infection in apolipoprotein E-knockout mice.
        Also, infected endothelial cells produce increased amounts of tissue factor, which is associated with thrombosis.
        • Fryer RH
        • Schwobe EP
        • Woods ML
        • Rodgers GM
        Chlamydia species infect human vascular endothelial cells and induce procoagulant activity.
      • 2.
        C pneumoniae has been shown to infect components of atherosclerotic plaque, including endothelial cells, foam cells, and smooth muscle cells.
        • Godzik KL
        • O'Brien ER
        • Wang SK
        • Kuo CC
        In vitro susceptibility of human vascular wall cells to infection with Chlamydia pneumoniae.
        • Kaukoranta-Tolvanen SS
        • Laitinen K
        • Saikku P
        • Leinonen M
        Chlamydia pneumoniae multiplies in human endothelial cells in vitro.
        • Kaukoranta-Tolvanen SS
        • Teppo AM
        • Laitinen K
        • et al.
        Growth of Chlamydia pneumoniae in cultured human peripheral blood mononuclear cells and induction of a cytokine response.
        In addition, C pneumoniae has been found in monocytes and macrophages; systemic circulation and transendothelial migration make them a potential vector system for chlamydial distribution.
        • Maass M
        • Gieffers J
        • Solbach W
        Atherogenetically relevant cells support continuous growth of Chlamydia pneumoniae.
        Macrophages infected with C pneumoniae are capable of transmitting infection to human coronary artery endothelial cells with direct cellular contact. Human coronary artery endothelial cells infected with C pneumoniae produce more interleukin 8 than do control cells.
        • Gaydos CA
        Growth in vascular cells and cytokine production by Chlamydia pneumoniae.
        Many studies have confirmed that infection with C pneumoniae is positively associated with inflammatory markers, including C-reactive protein, procoagulants (fibrinogen, plasminogen activator inhibitor 1, prostacyclin, factor VII), cytokines (interleukin 6, interleukin 8, tumor necrosis factor a), chemokines (monocyte chemotactic protein 1), nuclear factor-K B, and cellular adhesion molecules (intercellular and vascular cell adhesion molecule 1).
        • Kaukoranta-Tolvanen SS
        • Teppo AM
        • Laitinen K
        • et al.
        Growth of Chlamydia pneumoniae in cultured human peripheral blood mononuclear cells and induction of a cytokine response.
        • Gaydos CA
        Growth in vascular cells and cytokine production by Chlamydia pneumoniae.
        • Patel P
        • Mendall MA
        • Carrington D
        • et al.
        Association of Helicobacter pylori and Chlamydia pneumoniae infections with coronary heart disease and cardiovascular risk factors [published correction appears in BMJ. 1995;311:985].
        • Toss H
        • Gnarpe J
        • Gnarpe H
        • Siegbahn A
        • Lindahl B
        • Wallentin L
        Increased fibrinogen levels are associated with persistent Chlamydia pneumoniae infection in unstable coronary artery disease.
        • Patel P
        • Carrington D
        • Strachan DP
        • et al.
        Fibrinogen: a link between chronic infection and coronary heart disease [letter].
        • Anderson JL
        • Carlquist JF
        • Muhlestein JB
        • Horne BD
        • Elmer SP
        Evaluation of C-reactive protein, an inflammatory marker, and infectious serology as risk factors for coronary artery disease and myocardial infarction.
        • Mendall MA
        • Patel P
        • Ballam L
        • Strachan D
        • Northfield TC
        C reactive protein and its relation to cardiovascular risk factors: a population based cross sectional study.
        • Dechend R
        • Maass M
        • Gieffers J
        • et al.
        Chlamydia pneumoniae infection of vascular smooth muscle and endothelial cells activates NF-kappaB and induces tissue factor and PAI-1 expression: a potential link to accelerated arteriosclerosis.
        • Summersgill JT
        • Molestina RE
        • Miller RD
        • Ramirez JA
        Interactions of Chlamydia pneumoniae with human endothelial cells.
        In addition to plaque growth and the promotion of atherothrombosis, these factors contribute to weakening and plaque rupture at the shoulder region.
        • Gupta S
        Chlamydia pneumoniae, monocyte activation, and azithromycin in coronary heart disease.
        • Kol A
        • Lichtman AH
        • Finberg RW
        • Libby P
        • Kurt-Jones EA
        Cutting edge: heat shock protein (HSP) 60 activates the innate immune response: CD14 is an essential receptor for HSP60 activation of mononuclear cells.
        • Kalayoglu MV
        • Indrawati
        • Morrison RP
        • Morrison SG
        • Yuan Y
        • Byrne GI
        Chlamydial virulence determinants in atherogenesis: the role of chlamydial lipopolysaccharide and heat shock protein 60 in macrophage-lipoprotein interactions.
        • Kol A
        • Libby P
        Molecular mediators of arterial inflammation: a role for microbial products?.
      • 3.
        Components of C pneumoniae (ie, nonviable organisms) appear to have inflammatory effects. Several studies have reported that cardiovascular risk from prior chlamydial infection can be linked to certain antigens. Certain C pneumoniae antigens (40, 42, 52, 54, 60, 70, and 98 kd) appear to be more involved than others in the general immune response after infection, and chronic antibody responses to these may be associated with atherosclerosis.
        • Maass M
        • Gieffers J
        Cardiovascular disease risk from prior Chlamydia pneumoniae infection can be related to certain antigens recognized in the immunoblot profile.
        • Puolakkainen M
        • Kuo CC
        • Shor A
        • Wang SP
        • Grayston JT
        • Campbell LA
        Serological response to Chlamydia pneumoniae in adults with coronary arterial fatty streaks and fibrolipid plaques.
        • Linnanmaki E
        • Leinonen M
        • Mattila K
        • Nieminen MS
        • Valtonen V
        • Saikku P
        Chlamydia pneumoniae-specific circulating immune complexes in patients with chronic coronary heart disease.
        C pneumoniae endotoxin (lipopolysaccharide) has also been shown to induce inflammatory cytokines, increase low-density lipoprotein cholesterol uptake, and transform mononuclear phagocytes into foam cells.
        • Kalayoglu MV
        • Indrawati
        • Morrison RP
        • Morrison SG
        • Yuan Y
        • Byrne GI
        Chlamydial virulence determinants in atherogenesis: the role of chlamydial lipopolysaccharide and heat shock protein 60 in macrophage-lipoprotein interactions.
        • Kalayoglu MV
        • Byrne GI
        Induction of macrophage foam cell formation by Chlamydia pneumoniae.
        Other C pneumoniae products, including its heat shock protein 60, promote inflammation, can modulate oxidation of lipoproteins, and activate macrophage atherogenic functions.
        • Libby P
        Current concepts of the pathogenesis of the acute coronary syndromes.
        • Kol A
        • Lichtman AH
        • Finberg RW
        • Libby P
        • Kurt-Jones EA
        Cutting edge: heat shock protein (HSP) 60 activates the innate immune response: CD14 is an essential receptor for HSP60 activation of mononuclear cells.
        • Kol A
        • Libby P
        Molecular mediators of arterial inflammation: a role for microbial products?.
        • Kol A
        • Sukhova GK
        • Lichtman AH
        • Libby P
        Chlamydial heat shock protein 60 localizes in human atheroma and regulates macrophage tumor necrosis factor-alpha and matrix metalloproteinase expression.
        The latter inflammation may be due in part to antigenic mimicry or an immunological cross-reactivity between C pneumoniae heat shock protein 60 and selfantigens (because of a certain degree of genetic homology).
        • Mahdi OS
        • Horne BD
        • Mullen K
        • Muhlestein JB
        • Byrne GI
        Serum immunoglobulin G antibodies to chlamydial heat shock protein 60 but not to human and bacterial homologs are associated with coronary artery disease.
        This mimicry has been noted between C pneumoniae and the a myosin heavy chain of heart muscle.
        • Bachmaier K
        • Neu N
        • de la Maza LM
        • Pal S
        • Hessel A
        • Penninger JM
        Chlamydia infections and heart disease linked through antigenic mimicry.
      • 4.
        Several animal trials lend credence to the involvement of C pneumoniae in atherosclerosis. Intranasal C pneumoniae infection accelerates intimal thickening in rabbits given a modest cholesterol-enhanced diet; furthermore, weekly treatment with azithromycin after infectious exposure prevents accelerated intimal thickening.
        • Muhlestein JB
        • Anderson JL
        • Hammond EH
        • et al.
        Infection with Chlamydia pneumoniae accelerates the development of atherosclerosis and treatment with azithromycin prevents it in a rabbit model.
        In a similar rabbit model of atherosclerosis (nasopharyngeal inoculation with C pneumoniae), early treatment with azithromycin prevented atherosclerotic plaques; delayed treatment was ineffective.
        • Fong IW
        • Chiu B
        • Viira E
        • et al.
        Can an antibiotic (macrolide) prevent Chlamydia pneumoniae-induced atherosclerosis in a rabbit model?.
      Possible ways in which C pneumoniae may affect atherosclerotic lesions of CAD are listed in Table 1.
      Table 1Specific Factors That May Link Chlamydia pneumoniae Infection and Coronary Artery Disease
      • Systemic inflammation
        • Increased C-reactive protein
          • Anderson JL
          • Carlquist JF
          • Muhlestein JB
          • Horne BD
          • Elmer SP
          Evaluation of C-reactive protein, an inflammatory marker, and infectious serology as risk factors for coronary artery disease and myocardial infarction.
        • Increased leukocyte count
          • Anderson JL
          • Carlquist JF
          • Muhlestein JB
          • Horne BD
          • Elmer SP
          Evaluation of C-reactive protein, an inflammatory marker, and infectious serology as risk factors for coronary artery disease and myocardial infarction.
        • Increased cytokines (interleukin 6, interleukin 8, tumor necrosis factor α)
          • Kaukoranta-Tolvanen SS
          • Laitinen K
          • Saikku P
          • Leinonen M
          Chlamydia pneumoniae multiplies in human endothelial cells in vitro.
          • Gaydos CA
          Growth in vascular cells and cytokine production by Chlamydia pneumoniae.
          • Dechend R
          • Maass M
          • Gieffers J
          • et al.
          Chlamydia pneumoniae infection of vascular smooth muscle and endothelial cells activates NF-kappaB and induces tissue factor and PAI-1 expression: a potential link to accelerated arteriosclerosis.
        • Activated monocytes and monocyte integrins
          • Igietseme JU
          • Uriri IM
          • Hawkins R
          • Rank RG
          Integrin-mediated epithelial-T cell interaction enhances nitric oxide production and increased intracellular inhibition of Chlamydia.
      • Systemic infection
        • Endotoxin (lipopolysaccharide) secreted by C pneumoniae
          • Kalayoglu MV
          • Indrawati
          • Morrison RP
          • Morrison SG
          • Yuan Y
          • Byrne GI
          Chlamydial virulence determinants in atherogenesis: the role of chlamydial lipopolysaccharide and heat shock protein 60 in macrophage-lipoprotein interactions.
          • Kalayoglu MV
          • Byrne GI
          Induction of macrophage foam cell formation by Chlamydia pneumoniae.
          • Saikku P
          Epidemiologic association of Chlamydia pneumoniae and atherosclerosis: the initial serologic observation and more.
      • Endothelium
        • Endothelial dysfunction
          • Libby P
          Changing concepts of atherogenesis.
          • Liuba P
          • Karnani P
          • Pesonen E
          • et al.
          Endothelial dysfunction after repeated Chlamydia pneumoniae infection in apolipoprotein E-knockout mice.
          • Kaukoranta-Tolvanen SS
          • Laitinen K
          • Saikku P
          • Leinonen M
          Chlamydia pneumoniae multiplies in human endothelial cells in vitro.
          • Igietseme JU
          • Uriri IM
          • Hawkins R
          • Rank RG
          Integrin-mediated epithelial-T cell interaction enhances nitric oxide production and increased intracellular inhibition of Chlamydia.
          • Prasad A
          • Zhu J
          • Halcox JP
          • Waclawiw MA
          • Epstein SE
          • Quyyumi AA
          Predisposition to atherosclerosis by infections: role of endothelial dysfunction.
        • Enhanced expression of endothelial adhesion molecules
          • Krull M
          • Klucken AC
          • Wuppermann FN
          • et al.
          Signal transduction pathways activated in endothelial cells following infection with Chlamydia pneumoniae.
        • Increase in tissue factor
          • Fryer RH
          • Schwobe EP
          • Woods ML
          • Rodgers GM
          Chlamydia species infect human vascular endothelial cells and induce procoagulant activity.
          • Dechend R
          • Maass M
          • Gieffers J
          • et al.
          Chlamydia pneumoniae infection of vascular smooth muscle and endothelial cells activates NF-kappaB and induces tissue factor and PAI-1 expression: a potential link to accelerated arteriosclerosis.
        • Chlamydia heat shock protein 60
          • Kol A
          • Lichtman AH
          • Finberg RW
          • Libby P
          • Kurt-Jones EA
          Cutting edge: heat shock protein (HSP) 60 activates the innate immune response: CD14 is an essential receptor for HSP60 activation of mononuclear cells.
          • Kol A
          • Libby P
          Molecular mediators of arterial inflammation: a role for microbial products?.
          • Kol A
          • Sukhova GK
          • Lichtman AH
          • Libby P
          Chlamydial heat shock protein 60 localizes in human atheroma and regulates macrophage tumor necrosis factor-alpha and matrix metalloproteinase expression.
      • Vascular smooth muscle cells
        • Activate the nuclear factor for the expression of immunoglobulin κ light chain in the B-lymphocytes pathway (nuclear factor-κ B)
          • Dechend R
          • Maass M
          • Gieffers J
          • et al.
          Chlamydia pneumoniae infection of vascular smooth muscle and endothelial cells activates NF-kappaB and induces tissue factor and PAI-1 expression: a potential link to accelerated arteriosclerosis.
      • Activation of macrophages (macrophages ingest C pneumoniae)
        • Activation of monocyte-derived macrophages
          • Maass M
          • Gieffers J
          • Solbach W
          Atherogenetically relevant cells support continuous growth of Chlamydia pneumoniae.
          • Gupta S
          Chlamydia pneumoniae, monocyte activation, and azithromycin in coronary heart disease.
          • Kol A
          • Lichtman AH
          • Finberg RW
          • Libby P
          • Kurt-Jones EA
          Cutting edge: heat shock protein (HSP) 60 activates the innate immune response: CD14 is an essential receptor for HSP60 activation of mononuclear cells.
        • Alteration of cholesterol metabolism and lipid oxidation
          • Kalayoglu MV
          • Indrawati
          • Morrison RP
          • Morrison SG
          • Yuan Y
          • Byrne GI
          Chlamydial virulence determinants in atherogenesis: the role of chlamydial lipopolysaccharide and heat shock protein 60 in macrophage-lipoprotein interactions.
          • Kalayoglu MV
          • Byrne GI
          Induction of macrophage foam cell formation by Chlamydia pneumoniae.
      • Autoimmunity in genetically susceptible individuals
        • Cross-reactivity of bacterial antigens with vasculature (antigenic mimicry)
          • Chlamydia heat shock protein 60
            • Mahdi OS
            • Horne BD
            • Mullen K
            • Muhlestein JB
            • Byrne GI
            Serum immunoglobulin G antibodies to chlamydial heat shock protein 60 but not to human and bacterial homologs are associated with coronary artery disease.
            • Bachmaier K
            • Neu N
            • de la Maza LM
            • Pal S
            • Hessel A
            • Penninger JM
            Chlamydia infections and heart disease linked through antigenic mimicry.
          • Mycobacterial heat shock protein 65
            • Mayr M
            • Kiechl S
            • Willeit J
            • Wick G
            • Xu Q
            Infections, immunity, and atherosclerosis: associations of antibodies to Chlamydia pneumoniae, Helicobacter pylori, and cytomegalovirus with immune reactions to heat-shock protein 60 and carotid or femoral atherosclerosis.
        • Increased antibodies to specific C pneumoniae antigens (40, 42, 52,54, 60, 75, 98 kd)
          • Maass M
          • Gieffers J
          Cardiovascular disease risk from prior Chlamydia pneumoniae infection can be related to certain antigens recognized in the immunoblot profile.
          • Puolakkainen M
          • Kuo CC
          • Shor A
          • Wang SP
          • Grayston JT
          • Campbell LA
          Serological response to Chlamydia pneumoniae in adults with coronary arterial fatty streaks and fibrolipid plaques.
          • Linnanmaki E
          • Leinonen M
          • Mattila K
          • Nieminen MS
          • Valtonen V
          • Saikku P
          Chlamydia pneumoniae-specific circulating immune complexes in patients with chronic coronary heart disease.
      • Alteration of classic risk factors
        • Increased triglycerides
          • Laurila A
          • Bloigu A
          • Nayha S
          • Hassi J
          • Leinonen M
          • Saikku P
          Chronic Chlamydia pneumoniae infection is associated with a serum lipid profile known to be a risk factor for atherosclerosis.
          • Laurila AL
          • Bloigu A
          • Nayha S
          • Hassi J
          • Leinonen M
          • Saikku P
          Chlamydia pneumoniae antibodies associated with altered serum lipid profile.
        • Increased total cholesterol levels
          • Laurila A
          • Bloigu A
          • Nayha S
          • Hassi J
          • Leinonen M
          • Saikku P
          Chronic Chlamydia pneumoniae infection is associated with a serum lipid profile known to be a risk factor for atherosclerosis.
          • Murray LJ
          • O'Reilly DP
          • Ong GM
          • O'Neill C
          • Evans AE
          • Bamford KB
          Chlamydia pneumoniae antibodies are associated with an atherogenic lipid profile.
        • Decreased high-density lipoprotein cholesterol levels
          • Laurila A
          • Bloigu A
          • Nayha S
          • Hassi J
          • Leinonen M
          • Saikku P
          Chronic Chlamydia pneumoniae infection is associated with a serum lipid profile known to be a risk factor for atherosclerosis.
          • Laurila AL
          • Bloigu A
          • Nayha S
          • Hassi J
          • Leinonen M
          • Saikku P
          Chlamydia pneumoniae antibodies associated with altered serum lipid profile.
          • Murray LJ
          • O'Reilly DP
          • Ong GM
          • O'Neill C
          • Evans AE
          • Bamford KB
          Chlamydia pneumoniae antibodies are associated with an atherogenic lipid profile.
        • Increased lipoprotein(a) levels
          • Tutuncu NB
          • Guvener N
          • Tutuncu T
          • et al.
          Chlamydia pneumonia seropositivity correlates with serum fibrinogen and lipoprotein a levels: any role in atherosclerosis?.
        • Glucose intolerance
          • Leinonen M
          • Saikku P
          Interaction of Chlamydia pneumoniae infection with other risk factors of atherosclerosis.
      • Hypercoagulability
        • Increased fibrinogen
          • Toss H
          • Gnarpe J
          • Gnarpe H
          • Siegbahn A
          • Lindahl B
          • Wallentin L
          Increased fibrinogen levels are associated with persistent Chlamydia pneumoniae infection in unstable coronary artery disease.
          • Patel P
          • Carrington D
          • Strachan DP
          • et al.
          Fibrinogen: a link between chronic infection and coronary heart disease [letter].
          • Tutuncu NB
          • Guvener N
          • Tutuncu T
          • et al.
          Chlamydia pneumonia seropositivity correlates with serum fibrinogen and lipoprotein a levels: any role in atherosclerosis?.
          • Torgano G
          • Cosentini R
          • Mandelli C
          • et al.
          Treatment of Helicobacter pylori and Chlamydia pneumoniae infections decreases fibrinogen plasma level in patients with ischemic heart disease.
        • Increased thrombin
          • Valtonen VV
          Infection as a risk factor for infarction and atherosclerosis.
        • Increased expression of tissue factor (factor VIla antigen)
          • Fryer RH
          • Schwobe EP
          • Woods ML
          • Rodgers GM
          Chlamydia species infect human vascular endothelial cells and induce procoagulant activity.
          • Dechend R
          • Maass M
          • Gieffers J
          • et al.
          Chlamydia pneumoniae infection of vascular smooth muscle and endothelial cells activates NF-kappaB and induces tissue factor and PAI-1 expression: a potential link to accelerated arteriosclerosis.
        • Increased plasminogen activator inhibitor 1
          • Dechend R
          • Maass M
          • Gieffers J
          • et al.
          Chlamydia pneumoniae infection of vascular smooth muscle and endothelial cells activates NF-kappaB and induces tissue factor and PAI-1 expression: a potential link to accelerated arteriosclerosis.
        • Increased platelet accumulation/adhesion
          • Fryer RH
          • Schwobe EP
          • Woods ML
          • Rodgers GM
          Chlamydia species infect human vascular endothelial cells and induce procoagulant activity.
        • Enhanced activity of hemostatic and procoagulant mediators
          • Fryer RH
          • Schwobe EP
          • Woods ML
          • Rodgers GM
          Chlamydia species infect human vascular endothelial cells and induce procoagulant activity.
        • Increased circulating immune complexes
          • Saikku P
          Epidemiologic association of Chlamydia pneumoniae and atherosclerosis: the initial serologic observation and more.
          • Glader CA
          • Boman J
          • Saikku P
          • et al.
          The proatherogenic properties of lipoprotein(a) may be enhanced through the formation of circulating immune complexes containing Chlamydia pneumoniae-specific IgG antibodies.

      DETECTION OF C pneumoniae

      The meaning of anti-C pneumoniae IgG titers and the importance of their change is still debated. It is uncertain whether antibodies to C pneumoniae reflect active infection, past infection, chronic infection, or antigenic cross-reactivity. Also, it is unknown whether an anti-C pneumoniae IgG titer of 1:64 confers more or less of a risk than a titer of 1:16.
      Infection with C pneumoniae is ubiquitous in all populations with CAD that have been studied. Seropositivity is high and appears to increase with age and male sex, ranging from 20% to 84% in various population studies.
      • Patel P
      • Mendall MA
      • Carrington D
      • et al.
      Association of Helicobacter pylori and Chlamydia pneumoniae infections with coronary heart disease and cardiovascular risk factors [published correction appears in BMJ. 1995;311:985].
      • Ossewaarde JM
      • Feskens EJ
      • De Vries A
      • Vallinga CE
      • Kromhout D
      Chlamydia pneumoniae is a risk factor for coronary heart disease in symptom-free elderly men, but Helicobacter pylori and cytomegalovirus are not.
      • Karvonen M
      • Tuomilehto J
      • Pitkaniemi J
      • Saikku P
      The epidemic cycle of Chlamydia pneumoniae infection in eastern Finland, 1972-1987 [published correction appears in Epidemiol Infect. 1993;111:567].
      • Miettinen H
      • Lehto S
      • Saikku P
      • et al.
      Association of Chlamydia pneumoniae and acute coronary heart disease events in non-insulin dependent diabetic and non-diabetic subjects in Finland.
      Of the published epidemiological evidence, most studies have found a 1.5- to 2-fold larger odds ratio for CAD in individuals exposed to C pneumoniae.
      • Ossewaarde JM
      • Feskens EJ
      • De Vries A
      • Vallinga CE
      • Kromhout D
      Chlamydia pneumoniae is a risk factor for coronary heart disease in symptom-free elderly men, but Helicobacter pylori and cytomegalovirus are not.
      • Thom DH
      • Grayston JT
      • Siscovick DS
      • Wang SP
      • Weiss NS
      • Daling JR
      Association of prior infection with Chlamydia pneumoniae and angiographically demonstrated coronary artery disease.
      • Saikku P
      • Leinonen M
      • Tenkanen L
      • et al.
      Chronic Chlamydia pneumoniae infection as a risk factor for coronary heart disease in the Helsinki Heart Study.
      • Mendall MA
      • Carrington D
      • Strachan D
      • et al.
      Chlamydia pneumoniae: risk factors for seropositivity and association with coronary heart disease.
      However, some studies have found no association between C pneumoniae and CAD and/or its manifestations.
      • Ridker PM
      • Kundsin RB
      • Stampfer MJ
      • Poulin S
      • Hennekens CH
      Prospective study of Chlamydia pneumoniae IgG seropositivity and risks of future myocardial infarction.
      • Choussat R
      • Montalescot G
      • Collet J
      • et al.
      Effect of prior exposure to Chlamydia pneumoniae, Helicobacter pylori, or cytomegalovirus on the degree of inflammation and one-year prognosis of patients with unstable angina pectoris or non-Q-wave acute myocardial infarction.
      Results from various serologic studies are divergent because of differing populations and differing antibody serologic markers (eg, serum IgG, IgA, or IgM), sometimes in combination and at various “cutoff” levels. Odds ratios were adjusted for confounders to different extents, confounding was addressed to different depths, and study methods lent themselves to bias in differing areas. Also, subgroup analyses tended to be based on small numbers and therefore prone to statistical bias. The measuring instrument, primarily immunofluorescence and enzyme immunoassay, is operator dependent.
      • Danesh J
      • Collins R
      • Peto R
      Chronic infections and coronary heart disease: is there a link?.
      Also, titers of C pneumoniae antibody are not always positively associated with C pneumoniae organism in atheroma; they may reflect a cross-reactivity to non-C pneumoniae antigens.
      • Campbell LA
      • O'Brien ER
      • Cappuccio AL
      • et al.
      Detection of Chlamydia pneumoniae TWAR in human coronary atherectomy tissues.
      • Weiss SM
      • Roblin PM
      • Gaydos CA
      • et al.
      Failure to detect Chlamydia pneumoniae in coronary atheromas of patients under-going atherectomy.
      • Gupta S
      • Camm AJ
      Is there an infective aetiology to atherosclerosis?.
      Several DNA sequencing studies revealed no differences between coronary isolates and respiratory reference strains, suggesting that common respiratory strains gain access to the systemic circulation.
      • Blasi F
      • Tarsia P
      • Arosio C
      • Fagetti L
      • Allegra L
      Epidemiology of Chlamydia pneumoniae.
      However, serologic results (antichlamydial IgG, IgA, and IgM) do not always correlate with direct detection results or with individual endovascular infection.
      • Maass M
      • Bartels C
      • Engel PM
      • Mamat U
      • Sievers HH
      Endovascular presence of viable Chlamydia pneumoniae is a common phenomenon in coronary artery disease.
      Also, persons without measurable antibodies can show cell-mediated immunity to C pneumoniae, indicating that they have been exposed to the bacteria.
      • Halme S
      • von Hertzen L
      • Bloigu A
      • et al.
      Chlamydia pneumoniae-specific cell-mediated and humoral immunity in healthy people.
      In one study, some patients with C pneumoniae in their atherosclerotic plaques had no C pneumoniae antibodies.
      • Puolakkainen M
      • Kuo CC
      • Shor A
      • Wang SP
      • Grayston JT
      • Campbell LA
      Serological response to Chlamydia pneumoniae in adults with coronary arterial fatty streaks and fibrolipid plaques.
      A study of human atherectomy samples found no relationship between the frequency of C pneumoniae detection and C pneumoniae-specific antibody titers.
      • Muhlestein JB
      • Hammond EH
      • Carlquist JF
      • et al.
      Increased incidence of Chlamydia species within the coronary arteries of patients with symptomatic atherosclerotic versus other forms of cardiovascular disease.
      This raises the question, “What are we actually measuring with C pneumoniae serology?”
      Pathological studies vary in population, atheroma samples, and sensitivities and specificities of tests used (immunocytochemistry, polymerase chain reaction [PCR], enzyme immunoassay, electron microscopy, culture, immunofluorescence), and they do not rule out the possibility that C pneumoniae may be an innocent bystander in the process. In addition, uncertainties of results with PCR analysis and C pneumoniae occur and may reflect operator dependency; moreover, the detection rate (ranging from 0%-73%) may vary markedly with the number and type of primers used.
      • Weiss SM
      • Roblin PM
      • Gaydos CA
      • et al.
      Failure to detect Chlamydia pneumoniae in coronary atheromas of patients under-going atherectomy.
      • Muhlestein JB
      • Hammond EH
      • Carlquist JF
      • et al.
      Increased incidence of Chlamydia species within the coronary arteries of patients with symptomatic atherosclerotic versus other forms of cardiovascular disease.
      • Paterson DL
      • Hall J
      • Rasmussen SJ
      • Timms P
      Failure to detect Chlamydia pneumoniae in atherosclerotic plaques of Australian patients.
      • Davidson M
      • Kuo CC
      • Middaugh JP
      • et al.
      Confirmed previous infection with Chlamydia pneumoniae (TWAR) and its presence in early coronary atherosclerosis.
      Using more than 1 test may also improve detection rates.
      • Ouchi K
      • Fujii B
      • Kanamoto Y
      • Karita M
      • Shirai M
      • Nakazawa T
      Chlamydia pneumoniae in coronary and iliac arteries of Japanese patients with atherosclerotic cardiovascular diseases.
      Overall, study results support the finding of a high prevalence of C pneumoniae in atherosclerotic lesions. A logical extension of these pathological findings is whether these organisms detected inside coronary atherosclerotic lesions are alive or dead.
      In a study involving culturing of fresh atherosclerotic coronary artery specimens, a substantial proportion (16%) harbored viable C pneumoniae.
      • Maass M
      • Bartels C
      • Engel PM
      • Mamat U
      • Sievers HH
      Endovascular presence of viable Chlamydia pneumoniae is a common phenomenon in coronary artery disease.
      In a study of 12 cases, C pneumoniae was detected in 7; C pneumoniae was cultured from atherosclerotic plaques in only 1 patient with severe CAD.
      • Ramirez JA
      • Chlamydia pneumoniae/Atherosclerosis Study Group
      Isolation of Chlamydia pneumoniae from the coronary artery of a patient with coronary atherosclerosis.
      The organism was found in the atheromas of this patient by PCR assay, immunocytochemistry, electron microscopy, and in situ hybridization. In a study performed in Asia, C pneumoniae was detected by PCR and/or immuno-histochemical staining in 69% of 29 atherectomy specimens from patients with CAD; however, the investigators were unable to culture viable organisms from a single case.
      • Ouchi K
      • Fujii B
      • Kanamoto Y
      • Karita M
      • Shirai M
      • Nakazawa T
      Chlamydia pneumoniae in coronary and iliac arteries of Japanese patients with atherosclerotic cardiovascular diseases.
      These studies suggest that, although it is possible to culture live viable C pneumoniae organisms from coronary plaques, in most cases, culture comes back negative. This may reflect the difficulty in culturing C pneumoniae or the nonviability of the organism in storage (compared to fresh specimens). In contrast, this may suggest that after initial infection with C pneumoniae the body may destroy the organism, but the dead organism may then become a nidus for chronic inflammation.
      In summary, it remains unclear whether C pneumoniae actually initiates atherosclerotic injury, facilitates its progression, or merely colonizes preexisting atheromas.
      • Maass M
      • Bartels C
      • Kruger S
      • Krause E
      • Engel PM
      • Dalhoff K
      Endovascular presence of Chlamydia pneumoniae DNA is a generalized phenomenon in atherosclerotic vascular disease.

      RATIONALE FOR ANTIBIOTICS AND THEIR MECHANISMS

      Four classes of antibiotics have activity against C pneumoniae: quinolones, macrolides, tetracyclines, and anti-tuberculars (rifapentine, rifampin).
      • Gieffers J
      • Solbach W
      • Maass M
      In vitro susceptibility and eradication of Chlamydia pneumoniae cardiovascular strains from coronary artery endothelium and smooth muscle cells.
      Some classes appear to have anti-inflammatory activity. All the antibiotic trials reported thus far used macrolides, the focus of this section.
      Macrolide antibiotics have several anti-inflammatory effects. They affect migration of inflammatory cells and production of proinflammatory mediators, cytokines, and superoxide by activated leukocytes.
      • Parchure N
      • Zouridakis EG
      • Kaski JC
      Effect of azithromycin treatment on endothelial function in patients with coronary artery disease and evidence of Chlamydia pneumoniae infection.
      • Labro MT
      Anti-inflammatory activity of macrolides: a new therapeutic potential?.
      • Anderson R
      • Theron AJ
      • Feldman C
      Membrane-stabilizing, anti-inflammatory interactions of macrolides with human neutrophils.
      • Uriarte SM
      • Molestina RE
      • Miller RD
      • et al.
      Effect of macrolide antibiotics on human endothelial cells activated by Chlamydia pneumoniae infection and tumor necrosis factor-alpha.
      • Culic O
      • Erakovic V
      • Parnham MJ
      Anti-inflammatory effects of macrolide antibiotics.
      • Gorrini M
      • Lupi A
      • Viglio S
      • et al.
      Inhibition of human neutrophil elastase by erythromycin and flurythromycin, two macrolide antibiotics.
      By subduing inflammation, these antibiotics may stabilize atheromatous plaque, which may in part explain some of the benefits noted in the trials involving patients with acute coronary syndromes.
      Erythromycin increases constitutive nitric oxide synthase and thus nitric oxide release in human endothelial cells.
      • Mitsuyama T
      • Hidaka K
      • Furuno T
      • Hara N
      Release of nitric oxide and expression of constitutive nitric oxide synthase of human endothelial cells: enhancement by a 14-membered ring macrolide.
      Both erythromycin and roxithromycin have antioxidant properties.
      • Labro MT
      Anti-inflammatory activity of macrolides: a new therapeutic potential?.
      In a rat carrageenin pleurisy model of acute inflammation, roxithromycin appeared to be superior to clarithromycin and erythromycin in reducing the inflammatory reaction (measured by macrophage production of interleukin 1, interleukin 6, and tumor necrosis factor a); azithromycin had only a slight effect.
      • Ianaro A
      • Ialenti A
      • Maffia P
      • et al.
      Anti-inflammatory activity of macrolide antibiotics.
      A study investigating the potential anti-inflammatory activity of 3 macrolide antibiotics (azithromycin, roxithromycin, and clarithromycin) used an in vitro model of transendothelial migration. Both azithromycin and roxithromycin caused significant decreases in neutrophil and monocyte transendothelial migration (partially due to inhibition of interleukin 8 and monocyte chemotactic protein 1 production); clarithromycin had no detectable effect in either group. Azithromycin caused significant decreases in interleukin 8 and monocyte chemotactic protein 1, whereas roxithromycin significantly decreased interleukin 8. This study indicates heterogeneity in the anti-inflammatory activity of these antibiotics from the same class.
      • Uriarte SM
      • Molestina RE
      • Miller RD
      • et al.
      Effect of macrolide antibiotics on human endothelial cells activated by Chlamydia pneumoniae infection and tumor necrosis factor-alpha.
      A study of human cultured macrophages measured macrophage activity (Kor channel conductance) and compared roxithromycin and tetracycline.
      • Martin D
      • Bursill J
      • Qui MR
      • Breit SN
      • Campbell T
      Alternative hypothesis for efficacy of macrolides in acute coronary syndromes [letter].
      Roxithromycin (not tetracycline) produced significant reductions in whole-cell conductance, suggesting suppression of macrophage activity, which may partly explain its benefit in acute coronary syndromes.
      One crucial issue is whether antibiotics are bactericidal in all tissues. In one study, neither azithromycin nor rifampin inhibited C pneumoniae growth within monocytes. Thus, circulating monocytes carrying C pneumoniae with reduced antimicrobial susceptibility could initiate reinfection or promote atherosclerosis by the release of proin-flammatory mediators.
      • Gieffers J
      • Fullgraf H
      • Jahn J
      • et al.
      Chlamydia pneumoniae infection in circulating human monocytes is refractory to antibiotic treatment.
      In contrast, actively replicating C pneumoniae in coronary endothelial cells and smooth muscle cells can be eliminated with quinolones (ofloxacin, levofloxacin, trovafloxacin, and moxifloxacin), macrolides (erythromycin, azithromycin, and roxithromycin), and antituberculars (rifapentine and rifampin; rifampin was the most effective drug overall).
      • Gieffers J
      • Solbach W
      • Maass M
      In vitro susceptibility and eradication of Chlamydia pneumoniae cardiovascular strains from coronary artery endothelium and smooth muscle cells.
      Antibiotic susceptibility profiles of C pneumoniae strains recovered from arteriosclerotic coronary arteries were described recently.
      • Gieffers J
      • Solbach W
      • Maass M
      In vitro susceptibilities of Chlamydia pneumoniae strains recovered from atherosclerotic coronary arteries.
      In vitro susceptibilities to 5 cardiovascular C pneumoniae isolates did not differ significantly from respiratory strains in their patterns of susceptibility to azithromycin, erythromycin, roxithromycin, ofloxacin, doxycycline, rifampin, and penicillin G. Rox-ithromycin was the most active macrolide, and rifampin was the most effective drug overall.
      Sinisalo et al
      • Sinisalo J
      • Mattila K
      • Nieminen MS
      • et al.
      The effect of prolonged doxycycline therapy on Chlamydia pneumoniae serological markers, coronary heart disease risk factors and forearm basal nitric oxide production.
      investigated the effect of 4 months of doxycycline therapy on serologic markers of C pneumoniae infection and coronary risk factors, and they found no effect on C pneumoniae antibodies or CAD risk factors. In a small randomized study of patients with carotid atherosclerosis scheduled for surgery, C pneumoniae was eradicated in 69% (11/16) who received roxithromycin treatment (150 mg twice daily for 26 days) vs 25% (4/16) who did not receive treatment (P=.03).
      • Melissano G
      • Blasi F
      • Esposito G
      • et al.
      Chlamydia pneumoniae eradication from carotid plaques: results of an open, randomised treatment study.
      This suggests that roxithromycin is effective in reducing the bacterial burden of C pneumoniae within atherosclerotic plaques, although treatment for long periods may be required for complete eradication. In a randomized, prospective, double-blind, placebo-controlled trial of 40 male patients with documented CAD and positive C pneumoniae-IgG antibody titers, treatment with azithromycin for 5 weeks had a favorable affect on endothelial function irrespective of antibody titer levels; placebo had no effect.
      • Parchure N
      • Zouridakis EG
      • Kaski JC
      Effect of azithromycin treatment on endothelial function in patients with coronary artery disease and evidence of Chlamydia pneumoniae infection.
      Azithromycin therapy also resulted in a significant decrease of E-selectin and von Willebrand factor levels; however, C-reactive protein levels were not significantly altered by treatment with either azithromycin or placebo.
      In acute coronary syndromes, macrophages elaborate metalloproteinase enzymes (eg, collagenase, stromelysin, and gelatinase), which may digest structural components of the fibrous cap and predispose to plaque rupture. Tetracycline antibiotics have been shown to inhibit collagenase activity in vivo and in vitro. Macrolides may possess similar qualities.
      • Vaughan CJ
      Chronic infections and coronary heart disease [letter].
      Certain antibiotics or combinations may have greater efficacy. “Triple therapeutic” regimens have been used for another chronic infection of the stomach, Helicobacter pylori, with efficacy, but more research is needed.
      In summary, the effects of antibiotics begin to occur within 5 weeks and appear to occur irrespective of C pneumoniae serology; antibiotics do not affect IgG levels, but they do affect various mediators of inflammation and atherosclerosis (Table 2).
      Table 2Anti-inflammatory Effects of Macrolide Antibiotics
      • Endothelial function
        • Improved endothelial function (azithromycin)
          • Parchure N
          • Zouridakis EG
          • Kaski JC
          Effect of azithromycin treatment on endothelial function in patients with coronary artery disease and evidence of Chlamydia pneumoniae infection.
      • Cytokines (from monocytes or macrophages)
        • Decreased interleukin 1 (azithromycin, clarithromycin, roxithromycin)
          • Labro MT
          Anti-inflammatory activity of macrolides: a new therapeutic potential?.
          • Culic O
          • Erakovic V
          • Parnham MJ
          Anti-inflammatory effects of macrolide antibiotics.
          • Ianaro A
          • Ialenti A
          • Maffia P
          • et al.
          Anti-inflammatory activity of macrolide antibiotics.
        • Decreased interleukin 6 (azithromycin, clarithromycin, erythromycin, roxithromycin)
          • Labro MT
          Anti-inflammatory activity of macrolides: a new therapeutic potential?.
          • Culic O
          • Erakovic V
          • Parnham MJ
          Anti-inflammatory effects of macrolide antibiotics.
          • Ianaro A
          • Ialenti A
          • Maffia P
          • et al.
          Anti-inflammatory activity of macrolide antibiotics.
        • Decreased interleukin 8 (azithromycin, clarithromycin, erythromycin, roxithromycin)
          • Labro MT
          Anti-inflammatory activity of macrolides: a new therapeutic potential?.
          • Uriarte SM
          • Molestina RE
          • Miller RD
          • et al.
          Effect of macrolide antibiotics on human endothelial cells activated by Chlamydia pneumoniae infection and tumor necrosis factor-alpha.
        • Decreased tumor necrosis factor α (azithromycin, clarithromycin, erythromycin, roxithromycin)
          • Labro MT
          Anti-inflammatory activity of macrolides: a new therapeutic potential?.
          • Culic O
          • Erakovic V
          • Parnham MJ
          Anti-inflammatory effects of macrolide antibiotics.
          • Ianaro A
          • Ialenti A
          • Maffia P
          • et al.
          Anti-inflammatory activity of macrolide antibiotics.
        • Decreased granulocyte/monocyte colony-stimulating factor (clarithromycin)
          • Culic O
          • Erakovic V
          • Parnham MJ
          Anti-inflammatory effects of macrolide antibiotics.
        • Decreased monocyte chemotactic protein 1 (azithromycin)
          • Uriarte SM
          • Molestina RE
          • Miller RD
          • et al.
          Effect of macrolide antibiotics on human endothelial cells activated by Chlamydia pneumoniae infection and tumor necrosis factor-alpha.
      • Systemic inflammation
        • Decreased E-selectin (azithromycin)
          • Parchure N
          • Zouridakis EG
          • Kaski JC
          Effect of azithromycin treatment on endothelial function in patients with coronary artery disease and evidence of Chlamydia pneumoniae infection.
        • Decreased C-reactive protein (roxithromycin)
          • Gurfinkel E
          Inflammation, infection, or both in atherosclerosis: the ROXIS trial in perspective.
      • Alteration of classic risk factors
        • Antioxidant effects (erythromycin, roxithromycin)
          • Labro MT
          Anti-inflammatory activity of macrolides: a new therapeutic potential?.
      • Coagulation
        • Decreased von Willebrand factor levels (azithromycin)
          • Parchure N
          • Zouridakis EG
          • Kaski JC
          Effect of azithromycin treatment on endothelial function in patients with coronary artery disease and evidence of Chlamydia pneumoniae infection.

      RANDOMIZED CONTROLLED TRIALS

      Three main populations with positive C pneumoniae serology that were randomized to antibiotics have been studied.

      After Myocardial Infarction

      Gupta et al
      • Gupta S
      • Leatham EW
      • Carrington D
      • Mendall MA
      • Kaski JC
      • Camm AJ
      Elevated Chlamydia pneumoniae antibodies, cardiovascular events, and azithromycin in male survivors of myocardial infarction.
      at St George's Hospital in London performed a pilot trial that suggested a benefit with a brief course of azithromycin (3-6 days) in men who had had a myocardial infarction (MI) and had a high titer of anti-C pneumoniae IgG (Table 3). The WIZARD (Weekly Intervention with Zithromax for Atherosclerosis and its Related Disorders) trial was the logical extension of this pilot study. It used short-term treatment with azithromycin (3 months) and at a mean of 2.5 years’ follow-up found no significant effect on cardiovascular events (Table 3). There appeared to be an early benefit after treatment with azithromycin in the risk of MI, but it was not sustained.
      • Dunne M
      • O'Connor C
      • Pfeffer M
      • Muhlstein B
      • Gupta S
      • Yao L
      Weekly Intervention with Zithromax for Atherosclerosis and itsRelated Disorders (the WIZARD Study).
      The maximal benefit, although not significant, was obtained in smokers (hazard ratio, 0.76; 95% confidence interval [CI], 0.581.00; P=.05) and in diabetic patients (hazard ratio, 0.80; 95% CI, 0.64-1.01; P=.06). The WIZARD trial had 2 phases: 3300 patients were enrolled in the original trial; subsequently, the trial reopened enrollment and recruited to a total of 7724 patients. It would be instructive to know whether patients in the original cohort who were followed up longer (3 years vs 1.5 years) had a significant event reduction compared with those enrolled later. The small ongoing CROAATS (Croatian Azithromycin in Atherosclerosis Study) is analyzing the effect on cardiovascular events of approximately 3 weeks of azithromycin therapy given on 3 days to post-MI patients with 2 positive anti-C pneumoniae IgG titers obtained 2 months apart (Table 3).
      Table 3Randomized Controlled Trials of Antibiotics in Post-MI Patients
      CI = confidence interval; CROAATS = Croatian Azithromycin in Atherosclerosis Study; MI = myocardial infarction; NS = not significant; OR = odds ratio; WIZARD = Weekly Intervention with Zithromax for Atherosclerosis and its Related Disorders.
      TrialStudy populationTreatmentEnd pointResults
      St George's Hospital,
      Small pilot study.
      • Gupta S
      • Leatham EW
      • Carrington D
      • Mendall MA
      • Kaski JC
      • Camm AJ
      Elevated Chlamydia pneumoniae antibodies, cardiovascular events, and azithromycin in male survivors of myocardial infarction.
      London
      220 consecutive male outpatients tested for IgG to Chlamydia pneumoniae; C pneumoniae negative, anti-C pneumoniae IgG 1:8-1:32 and anti-C pneumoniae IgG ≥1:64Randomized patients with IgG ≥1:64 to 3-6 days of azithromycin, 500 mg/d, or placebo; follow-up, 18 moPrimary (composite): nonfatal MI, unstable angina, cardiovascular death

      Secondary: anti-C pneumoniae titers
      • IgG anti-C pneumoniae negative; OR, 1.0
      • IgG, 1:8-1:32; OR, 2.0 (P=.10)
      • IgG ≥1:64 plus azithromycin; OR, 0.9 (P=NS)
      • IgG ≥1:64 plus placebo; OR, 4.2 (95% CI, 1.2-15.5; P=.03 vs group C pneumoniae negative)
      • 43% of azithromycin-treated patients had a decrease in anti-C pneumoniae titers compared with 10% of controls (P=.02)
      WIZARD
      • Dunne MW
      Rationale and design of a secondary prevention trial of antibiotic use in patients after myocardial infarction: the WIZARD (weekly intervention with zithromax [azithromycin] for atherosclerosis and its related disorders) trial.
      Best of the ACC Scientific Session 2002: highlights from the American College of Cardiology 51st Annual Scientific Session, March 17-20, 2002, Atlanta, GA.
      international multicenter trial
      7724 patients (83% male) ≥18 y with documented MI (>6 wk post-MI); IgG anti-C pneumoniae titer ≥1:16Azithromycin (Zithromax) for 3 mo (600 mg/d for 3 days, then 600 mg every week for 11 wk) vs placebo; mean follow-up, 2.5 yPrimary (composite): recurrent MI, all-cause mortality, revascularization, hospitalization for angina/ischemia

      Secondary: anti-C pneumoniae titers, levels of C-reactive protein, tumor necrosis factor a, and fibrinogen
      No significant reduction in the primary composite end point (hazard ratio 0.93; P=.23) or in any of the end point components: baseline titer of IgG antibodies against C pneumoniae had no effect on outcome
      CROAATS,
      • Reiner Z
      • CROAATS Study Group
      Azithromycin in the secondary prevention of adverse cardiovascular events in C. pneumoniae-positive post-myocardial infarction patients (CROAATS) [abstract].
      Zagreb, Croatia
      340 patients with documented MI and 2 seropositive serum samples (IgG anti-C pneumoniae titer ≥ 1:20) obtained 2 mo apart at 6 study sitesAzithromycin, 3 cycles of 500 mg once daily for 3 days, starting on days 1, 10, and 20 (total dose, 4500 mg) vs placebo; follow-up, 18 mo
      • Primary: death due to cardiac ischemia and/or related complications, MI, revascularization, and hospitalization for unstable angina
      • Secondary: anti-C pneumoniae titers, levels of C-reactive protein, tumor necrosis factor α, and fibrinogen
      Expected in 2004
      * CI = confidence interval; CROAATS = Croatian Azithromycin in Atherosclerosis Study; MI = myocardial infarction; NS = not significant; OR = odds ratio; WIZARD = Weekly Intervention with Zithromax for Atherosclerosis and its Related Disorders.
      Small pilot study.
      In summary, short-term antibiotic treatment in patients with a history of MI and positive C pneumoniae titers does not significantly reduce cardiovascular events.

      Coronary Artery Disease

      In the ACADEMIC (Azithromycin in Coronary Artery Disease: Elimination of Myocardial Infection with Chlamydia) study, azithromycin treatment for 3 months did not affect cardiovascular events, but at 6 months, it reduced inflammatory markers. The ACADEMIC study defined chronic CAD as previous MI, bypass surgery, or greater than 50% angiographic stenosis of one or more major coronary arteries. C pneumoniae antibody titers were unchanged (Table 4).
      • Anderson JL
      • Muhlestein JB
      The ACADEMIC study in perspective (Azithromycin in Coronary Artery Disease: Elimination of Myocardial Infection with Chlamydia).
      ACES (Azithromycin and Coronary Events Study) is unique in that it will treat patients with azithromycin for 1 year; also, seropositivity to C pneumoniae is not an inclusion criterion (but the investigators expect about 80% of patients to be seropositive with an IgG titer ≥1:8). In addition, ACES will study C pneumoniae DNA (detected by PCR) located in peripheral blood mononuclear cells (Table 4). The ongoing MARBLE (Might Azithromycin Reduce Bypass List Events?) trial is treating patients who are awaiting bypass surgery with long-term antibiotic therapy in an attempt to decrease cardiovascular events (Table 4).
      Table 4Randomized Controlled Trials of Antibiotics for CAD
      ACADEMIC = Azithromycin in Coronary Artery Disease: Elimination of Myocardial Infection with Chlamydia; ACES = Azithromycin and Coronary Events Study; CAD = coronary artery disease; MARBLE = Might Azithromycin Reduce Bypass List Events?; MI = myocardial infarction.
      TrialStudy populationTreatmentEnd pointResults
      ACADEMIC
      • Anderson JL
      • Muhlestein JB
      • Carlquist J
      • et al.
      Randomized secondary prevention trial of azithromycin in patients with coronary artery disease and serological evidence for Chlamydia pneumoniae infection: the Azithromycin in Coronary Artery Disease: Elimination of Myocardial Infection with Chlamydia (ACADEMIC) study.
      • Anderson JL
      • Muhlestein JB
      The ACADEMIC study in perspective (Azithromycin in Coronary Artery Disease: Elimination of Myocardial Infection with Chlamydia).
      302 patients (89% men) with chronic CAD (previous MI, bypass surgery, or >50% angiographic stenosis of ≥1 major coronary artery), >18 y, IgG anti-Chlamydia pneumoniae titer ≥1:163 mo of azithromycin treatment (500 mg/d for 3 days then 500 mg/wk) vs placebo; follow-up, 6 mo
      • Primary: cardiovascular events (cardiovascular death, nonfatal MI or stroke, hospitalization for unstable angina, resuscitated cardiac arrest, revascularization)
      • Secondary: inflammatory markers
      Clinical cardiovascular events at 6 mo did not differ between groups; azithromycin reduced a global rank sum score of 4 inflammatory markers (C-reactive protein, interleukin 1, interleukin 6, tumor necrosis factor α; P=.01) at 6 (but not 3) mo; C pneumoniae IgG and IgA antibody titers were unchanged
      ACES
      • Jackson LA
      Description and status of the Azithromycin and Coronary Events Study (ACES).
      4000 patients with stable CAD (previous MI, bypass surgery, or >50% angiographic stenosis of ≥1 major coronary artery, revascularization)Azithromycin, 600 mg/wk for 1 y vs placebo; follow-up, 4 y
      • Primary (composite): CAD death, nonfatal MI, hospitalization for unstable angina, revascularization
      • Secondary: relationship among antibody titer, inflammatory markers, treatment status, and outcome
      Expected in 2004
      MARBLE,
      • Gupta S
      Chlamydia pneumoniae, monocyte activation and azithromycin therapy in coronary heart disease.
      London
      1240 patients with known CAD on waiting list for elective coronary artery bypass surgery randomized while waiting for surgeryChronic antibiotic therapy in addition to concomitant antianginal medicationPrimary: cardiovascular eventsExpected in 2003
      * ACADEMIC = Azithromycin in Coronary Artery Disease: Elimination of Myocardial Infection with Chlamydia; ACES = Azithromycin and Coronary Events Study; CAD = coronary artery disease; MARBLE = Might Azithromycin Reduce Bypass List Events?; MI = myocardial infarction.
      In summary, no large randomized controlled trial has shown a significant reduction in cardiovascular events with short-term antibiotic treatment in patients with a history of chronic CAD and positive C pneumoniae titers; a possible benefit on inflammatory markers was suggested in one small trial.

      Acute Coronary Syndromes

      About one half of patients with acute coronary syndromes have positive C pneumoniae serology. Of necessity, all trials in such patients use the “blanket approach” and treat all patients irrespective of C pneumoniae serology.
      The small ROXIS (Randomized Trial of Roxithromycin in Non-Q-Wave Coronary Syndromes) pilot trial suggested a possible benefit of roxithromycin (due to antimicrobial or anti-inflammatory effects) in patients with non-Q-wave coronary syndromes (Table 5). Because less than half of roxithromycin- or placebo-treated patients were seropositive (IgG anti-C pneumoniae titer ≥1:64) and no association was shown between the efficacy of roxithromycin and IgG titers, it is likely that roxithromycin's anti-inflammatory effects played a role.
      • Gurfinkel E
      • Bozovich G
      • Beck E
      • Testa E
      • Livellara B
      • Mautner B
      Treatment with the antibiotic roxithromycin in patients with acute non-Q-wave coronary syndromes: the final report of the ROXIS Study.
      C-reactive protein, a marker of inflammation and a predictor of future cardiac events, differed in the 2 groups.
      • Ridker PM
      • Cushman M
      • Stampfer MJ
      • Tracy RP
      • Hennekens CH
      Inflammation, aspirin, and the risk of cardiovascular disease in apparently healthy men [published correction appears in N Engl J Med. 1997;337:356].
      • Ridker PM
      • Buring JE
      • Shih J
      • Matias M
      • Hennekens CH
      Prospective study of C-reactive protein and the risk of future cardiovascular events among apparently healthy women.
      • Doggen CJ
      • Berckmans RJ
      • Sturk A
      • Manger Cats V
      • Rosendaal FR
      C-reactive protein, cardiovascular risk factors and the association with myocardial infarction in men.
      • Tomoda H
      • Aoki N
      Prognostic value of C-reactive protein levels within six hours after the onset of acute myocardial infarction.
      In those with a positive response, C-reactive protein levels decreased from 53.7% to 35.8% at day 31 in the roxithromycin group vs 47.4% to 31.3% in the placebo group (P=.03). Within an unstable atherosclerotic plaque, such attenuation of inflammation could result in a more stable state and fewer subsequent cardiovascular events. In support of this, patients with positive IgG titers and elevated C-reactive protein levels were more likely to experience a recurrent ischemic event than those with negative IgG titers and low C-reactive protein levels (43% vs 9%; P=.03).
      Table 5Randomized Controlled Trials of Antibiotics for Acute Coronary Syndromes
      AZACS = Azithromycin in Acute Coronary Syndromes; CLARIFY = Clarithromycin in Acute Coronary Syndrome patients in Finland; MI = myocardial infarction; PROVE IT = Pravastatin or Atorvastatin Evaluation and Infection Therapy; ROXIS = Randomized Trial of Roxithromycin in Non-Q-Wave Coronary Syndromes; STAMINA = South Thames Trial of Antibiotics in Myocardial Infarction and Unstable Angina.
      TrialStudy populationTreatmentEnd pointResults
      AZACS
      • Williams ES
      • Miller JM
      Results from late-breaking clinical trial sessions at the American College of Cardiology 51st Annual Scientific Session.
      1439 patients (74% men) enrolled shortly after admission for acute coronary syndrome. 826 of whom had acute MIAzithromycin (single dose of 500 mg followed by 4 days of 250 mg initiated 3-4 days after admission) vs placebo; follow-up, 6 moPrimary (composite): death, cardiac arrest, nonfatal MI, and revascularizationNo significant difference in composite primary end point (12.6% in placebo vs 12.3% in azithromycin group; P=NS)
      Secondary: unstable angina, congestive heart failure
      CLARIFY
      • Sinisalo J
      • Mattila K
      • Valtonen V
      • et al.
      Effect of 3 months of antimicrobial treatment with clarithromycin in acute non-q-wave coronary syndrome.
      148 patients (70% men), 105 with non-Q-wave MI and 43 with unstable anginaClarithromycin (500 mg/d) for 85 days vs placeboPrimary (composite): death, MI, or unstable anginaNo significant difference in primary end point within 3 mo (19 events in placebo vs 11 events in clarithromycin group; P=. 10); significant difference in secondary end point throughout mean follow-up (median, 555 days): 27 events in placebo vs 16 events in clarithromycin group, risk ratio, 0.49; P=.03
      Secondary: death, MI, unstable angina, ischemic stroke, and critical limb ischemia
      ROXIS,
      Pilot trial.
      • Gurfinkel E
      • Bozovich G
      • Beck E
      • Testa E
      • Livellara B
      • Mautner B
      Treatment with the antibiotic roxithromycin in patients with acute non-Q-wave coronary syndromes: the final report of the ROXIS Study.
      Argentina
      202 patients (76% men) with unstable angina from 8 coronary care units; age >21 yRoxithromycin (150 mg twice daily) for 30 days vs placebo; follow-up, 6 moPrimary (composite): cardiac ischemic death, MI, severe recurrent ischemia

      Secondary: anti-Chlamydia pneumoniae IgG titers, C-reactive protein
      Day 30: the primary triple end point rates were 9% in placebo vs 2% in roxithromycin group (P=.03) Day 90: 12.5% vs 4.37%, respectively (P=.06) Day 180: 14.6% vs 8.69%, respectively (P=.26)
      PROVE IT
      • Cannon CP
      • McCabe CH
      • Belder R
      • Breen J
      • Braunwald E
      Design of the Pravastatin or Atorvastatin Evaluation and Infection Therapy (PROVE IT)-TIMI 22 trial.
      4000 patients with acute coronary syndrome for <10 days and a total cholesterol level of 150-240 mg/dL2 by 2 factorial trial of pravastatin vs atorva-statin and gatifloxacin (400 mg/d for 10 days, then 10 days per month for trial duration) vs placebo; follow-up, 2 yPrimary: death, MI, stroke, hospitalization for angina, revascularization

      Secondary: lipid levels, high-sensitivity C-reactive protein, anti-C pneumoniae IgG titers
      Expected in 2005
      Single-center trial,
      • Leowattana W
      • Bhuripanyo K
      • Singhaviranon L
      • et al.
      Roxithromycin in prevention of acute coronary syndrome associated with Chlamydia pneumoniae infection: a randomized placebo controlled trial.
      Siriraj Hospital
      84 patients with acute coronary syndrome admitted to a single hospital in Bangkok. ThailandRoxithromycin (150 mg twice daily) for 30 days vs placebo; follow-up, 90 daysPrimary: cardiac death, unplanned revascularization, recurrent angina/MlNo significant difference in cardiac events (17 in roxithromycin vs 16 in placebo group); anti-C pneumoniae IgG positivity was 55.8% in roxithromycin vs 56.1% in placebo group
      Secondary: anti-C pneumoniae titers (IgG and IgA)
      STAMINA
      • Stone AF
      • Mendall MA
      • Kaski JC
      • et al.
      Effect of treatment for Chlamydia pneumoniae and Helicobacter pylori on markers of inflammation and cardiac events in patients with acute coronary syndromes: South Thames Trial of Antibiotics in Myocardial Infarction and Unstable Angina (STAMINA).
      324 patients from 4 hospitals in south London admitted with an acute coronary syndrome (MI or unstable angina)Antibiotics given during hospitalization: azithromycin, metronidazole, and omeprazole; amoxicillin, metronidazole, and omeprazole; or placebo; follow-up, 1 yPrimary: unstable angina or MIPatients who received antibiotic therapy with either azithromycin or amoxicillin had a 40% reduction in unstable angina or MI
      Secondary: antibodies to C pneumoniae and Helicobacter pylori
      * AZACS = Azithromycin in Acute Coronary Syndromes; CLARIFY = Clarithromycin in Acute Coronary Syndrome patients in Finland; MI = myocardial infarction; PROVE IT = Pravastatin or Atorvastatin Evaluation and Infection Therapy; ROXIS = Randomized Trial of Roxithromycin in Non-Q-Wave Coronary Syndromes; STAMINA = South Thames Trial of Antibiotics in Myocardial Infarction and Unstable Angina.
      Pilot trial.
      The small single-center study at Siriraj Hospital in Bangkok used the same protocol as ROXIS and found no significant difference in events at 90 days (Table 5).
      The AZACS (Azithromycin in Acute Coronary Syndromes) trial enrolled 1439 patients (74% men) shortly after admission for acute coronary syndrome.
      Best of the ACC Scientific Session 2002: highlights from the American College of Cardiology 51st Annual Scientific Session, March 17-20, 2002, Atlanta, GA.
      • Williams ES
      • Miller JM
      Results from late-breaking clinical trial sessions at the American College of Cardiology 51st Annual Scientific Session.
      After a brief course of azithromycin vs placebo, no significant difference was noted in composite primary end point (death, cardiac arrest, nonfatal MI, and revascularization) (12.6% in placebo group vs 12.3% in azithromycin group; P=NS) or in any of its components. Also, there was no difference in rates of end points in patients enrolled with acute MI or with antibodies to C pneumoniae (Table 5).
      CLARIFY (Clarithromycin in Acute Coronary Syndrome patients in Finland) treated patients with non-Q-wave MI or unstable angina with clarithromycin or placebo for 85 days and found a trend toward reduced primary end point events (death, MI, or unstable angina) at 3 months.
      • Sinisalo J
      • Mattila K
      • Valtonen V
      • et al.
      Effect of 3 months of antimicrobial treatment with clarithromycin in acute non-q-wave coronary syndrome.
      When all cardiovascular events were included (secondary end point), there was a significant reduction in events, beginning at the 3-month period and continuing until about 10 months, then remaining approximately the same thereafter (Table 5). Compared to ROXIS, CLARIFY had more patients with first-time angina and fewer patients with previous MI or revascularizations; however, the patients’ condition was more unstable, with the number of events during the first 3 months in the placebo groups being higher (26% in CLARIFY vs 13% in ROXIS). CLARIFY suggests that the beneficial effect starts during the treatment phase (3 months) and continues for at least another 7 months (continued separation of event curves).
      In STAMINA (South Thames Trial of Antibiotics in Myocardial Infarction and Unstable Angina), the antibiotics selected (triple therapy analogous to that used to eradicate H pylori in gastric ulcers) were aimed at controlling infection by both C pneumoniae and H pylori (Table 5). The surprising finding in this small study was that the antibiotics produced beneficial effects whether or not the patient was a carrier of one or both infections. This suggests that the antibiotics may be working either against a different infection or in an alternative manner.
      • Stone AF
      • Mendall MA
      • Kaski JC
      • et al.
      Effect of treatment for Chlamydia pneumoniae and Helicobacter pylori on markers of inflammation and cardiac events in patients with acute coronary syndromes: South Thames Trial of Antibiotics in Myocardial Infarction and Unstable Angina (STAMINA).
      PROVE IT (Pravastatin or Atorvastatin Evaluation and Infection Therapy) is a well-powered study (N=4000) examining long-term use of gatifloxacin in patients presenting with an acute coronary syndrome and elevated cholesterol levels; results are expected in 2005 (Table 5).
      In summary, in patients with acute coronary syndromes, no large well-powered randomized controlled trial has been completed. Results of available trials have been mixed. Two small trials showed benefit on total cardiovascular events (ROXIS, CLARIFY); one small pilot trial showed a decrease in events with several triple therapeutic antibiotic regimens (STAMINA).

      POSSIBLE EXPLANATIONS FOR STUDY RESULTS

      Period of Antibiotic Treatment Too Brief

      The main reason that the previously mentioned studies did not extend azithromycin therapy beyond a few months is that safety and efficacy data on long-term treatment are lacking. Long-term administration may be required to exert chronic anti-C pneumoniae, anti-inflammatory, or other effects beneficial to plaque remodeling and stabilization. This may be analogous to the anti-inflammatory effects of statins, which lead to greater divergence of treatment and placebo event curves over the long term.
      AZACS used treatment for only 5 days, and patients in WIZARD received azithromycin once weekly for 3 months; neither trial showed a significant cardiovascular effect. In AZACS, a small, early separation of time-to-event curves was visually apparent, but the curves came together and then crossed 2 months after the 4-day treatment course ended.
      • Williams ES
      • Miller JM
      Results from late-breaking clinical trial sessions at the American College of Cardiology 51st Annual Scientific Session.
      In addition, in WIZARD, a secondary treatment-by-time analysis at 6 months showed a significant reduction of 33% in the secondary end point of death or MI (relative risk, 0.67; 95% CI, 0.48-0.94).
      • Williams ES
      • Miller JM
      Results from late-breaking clinical trial sessions at the American College of Cardiology 51st Annual Scientific Session.
      Thus, AZACS and WIZARD support an early benefit after treatment in the risk of MI and a possible waning of effect once the active treatment is discontinued. This would be consistent with a cytostatic rather than a cytocidal effect of the short course of the antibiotic.
      • Williams ES
      • Miller JM
      Results from late-breaking clinical trial sessions at the American College of Cardiology 51st Annual Scientific Session.
      In the small ROXIS pilot trial (treatment period 1 month), there was a decrease in the triple end point at 1 month, which became nonsignificant as time advanced after the last antibiotic dose. Roxithromycin, a second-generation macrolide used in ROXIS, may have differing effects on inflammation than other macrolides.
      • Uriarte SM
      • Molestina RE
      • Miller RD
      • et al.
      Effect of macrolide antibiotics on human endothelial cells activated by Chlamydia pneumoniae infection and tumor necrosis factor-alpha.
      In addition, reinfection by C pneumoniae (eg, from peripheral monocytes containing viable C pneumoniae) during the antibiotic-free follow-up period may have led to further infection, inflammation, and instability of the plaque by C pneumoniae and thus excess cardiac events.
      • Gurfinkel E
      • Bozovich G
      • Beck E
      • Testa E
      • Livellara B
      • Mautner B
      Treatment with the antibiotic roxithromycin in patients with acute non-Q-wave coronary syndromes: the final report of the ROXIS Study.
      CLARIFY supports the notion that benefits occur during the treatment phase, which was longer than that in ROXIS (3 months vs 1 month), but also for several months after the treatment phase is completed. The survival curves separated further as the treatment phase continued, again supporting the hypothesis that a longer duration of antibiotic treatment is necessary.
      After 3 months of treatment in ACADEMIC (a small trial), there was no significant effect on cardiovascular primary end points; however, there was a significant improvement in inflammatory markers at 6 months but not at 3 months. This suggests that a longer duration of treatment may result in greater anti-inflammatory effects; there also may be a lag effect of antibiotic treatment on subsequent inflammation.
      Two large studies are treating patients with antibiotics for a longer period: 1 year of azithromycin (a macrolide) in ACES and 2 years of gatifloxacin (a quinolone) in PROVE IT. These trials will test the hypothesis that long-term antibiotic treatment decreases cardiovascular events.

      C pneumoniae Antibody Titers May Be Misleading

      As discussed earlier, all serologic tests are not equal, and many uncertainties still exist regarding the meaning of anti-C pneumoniae IgG titers. Of the clinical trials, WIZARD found that titer levels had no effect on outcome. Intervention with antibiotics did not affect titer levels in ACADEMIC or ROXIS, and cardiac events or anti-inflammatory effects occurred independent of anti-C pneumoniae IgG titers in ACADEMIC and STAMINA. Another pilot study (of patients who had undergone percutaneous transluminal coronary angioplasty) of 1 month of azithromycin treatment (8 g) found no effect on anti-C pneumoniae antibody titers.
      • Jackson LA
      • Stewart DK
      • Wang SP
      • Cooke DB
      • Cantrell T
      • Grayston JT
      Safety and effect on anti-Chlamydia pneumoniae antibody titres of a 1 month course of daily azithromycin in adults with coronary artery disease.
      These studies suggest that IgG titers may be an inadequate marker for guiding treatment.
      • Gurfinkel E
      Is there something more behind atherosclerotic plaque inflammation? [editorial].
      In a study of acute ischemic heart disease, PCR detected C pneumoniae DNA in peripheral blood mononuclear cells in 26% of patients (24/93) vs 5% of healthy subjects (2/42) (P=.008) and anti-C pneumoniae IgG in 76% vs 45% (P<.001), respectively.
      • Sessa R
      • Di Pietro M
      • Schiavoni G
      • et al.
      Prevalence of Chlamydia pneumoniae in peripheral blood mononuclear cells in Italian patients with acute ischaemic heart disease.
      A study of 95 patients with angiographically confirmed CAD and 104 healthy volunteers detected C pneumoniae DNA in peripheral blood mononuclear cells in 17% and 1%, respectively (odds ratio, 20.86; 95% CI, 2.71-160.67; P<.001).
      • Leowattana W
      • Pokum S
      • Mahanonda N
      • Poungvarin N
      Rapid detection of Chlamydia pneumoniae DNA in peripheral blood mononuclear cells of coronary artery disease patients by real-time fluorescence PCR.
      Both studies showed no correlation between anti-C pneumoniae antibody titers and positive PCR results for C pneumoniae DNA in peripheral blood mononuclear cells. Viable C pneumoniae has been cultured from peripheral blood mononuclear cells.
      • Kaukoranta-Tolvanen SS
      • Teppo AM
      • Laitinen K
      • et al.
      Growth of Chlamydia pneumoniae in cultured human peripheral blood mononuclear cells and induction of a cytokine response.
      Of note, PCR assays for C pneumoniae are still being refined.
      • Mahony JB
      • Chong S
      • Coombes BK
      • Smieja M
      • Petrich A
      Analytical sensitivity, reproducibility of results, and clinical performance of five PCR assays for detecting Chlamydia pneumoniae DNA in peripheral blood mononuclear cells.
      These results raise the question, “Does detection of C pneumoniae in peripheral blood mononuclear cells aid in selecting which patients may benefit from antibiotics?”

      CONCLUSION

      The potential role of C pneumoniae in coronary atherosclerosis may be more related to acceleration of disease or systemic effects by persistent infection than to sudden initiation of infarction by acute infection.
      • Maass M
      • Jahn J
      • Gieffers J
      • Dalhoff K
      • Katus HA
      • Solbach W
      Detection of Chlamydia pneumoniae within peripheral blood monocytes of patients with unstable angina or myocardial infarction.
      Whether patients with CAD or acute coronary syndromes benefit from antibiotics is an evolving issue. Short-term antibiotic treatment in patients with CAD and positive C pneumoniae serology does not significantly decrease cardiovascular events. One robust study (ACES) should determine whether long-term treatment is required to decrease cardiac events.
      Several small trials have suggested that treating acute coronary syndromes with antibiotics may be beneficial, regardless of C pneumoniae serology. A large well-powered trial (PROVE IT) with long-term antibiotic treatment may shed light on this subject.
      A proposed model for C pneumoniae, antibiotics, and CAD based on the available data is as follows. C pneumoniae infection may have a direct noxious effect on the arterial wall, which may initiate and accelerate the atherosclerotic process. Alternatively, C pneumoniae may induce other inflammatory, oxidant, or thrombotic factors. Antibiotics (eg, macrolides, quinolones, tetracyclines, or anti-tuberculars) may affect CAD through their antichlamydial action (bacteriostatic or bacteriocidal), through other factors (anti-inflammatory, antioxidant, or antithrombotic), via a direct effect, or some combination of these. Vaccination before initial exposure may be the best approach, and the vaccine TWARVAX (AntexBiologics Inc, Gaithersburg, Md) is being actively investigated. In producing this vaccine, functional genomics were used, and a family of novel proteins in C pneumoniae were cloned and expressed recombinantly. TWARVAX is currently being evaluated in preclinical models as a potential subunit vaccine to treat and prevent chronic C pneumoniae infection.

      TWARVAX. Gaithersburg, Md: Antex Biologics Inc. Available at: www.antexbiologics.com/antexbio/twarvax.phtm. Accessibility verified January 15, 2003.

      At this time, several points are clear. (1) C pneumoniae serology by itself does not assist in identifying persons who might benefit from antibiotic treatment. This serology in combination with inflammatory markers may have better predictive value. (2) Anti-inflammatory effects are clearly manifesting in patients treated with macrolides and may be the conduit through which the benefits are occurring. (3) Combinations of antibiotics, including triple therapy, may be superior to single antibiotic therapy. (4) A longer duration of antibiotic therapy is probably important in providing continued bactericidal-cytocidal (rather than cytostatic) and anti-inflammatory effects. (5) Overall pathogen burden is probably important in inflammation and atherosclerosis, and pilot studies of antibiotic strategies (eg, triple therapy) against several pathogens appear to be effective.
      • Prasad A
      • Zhu J
      • Halcox JP
      • Waclawiw MA
      • Epstein SE
      • Quyyumi AA
      Predisposition to atherosclerosis by infections: role of endothelial dysfunction.
      • Zhu J
      • Nieto FJ
      • Horne BD
      • Anderson JL
      • Muhlestein JB
      • Epstein SE
      Prospective study of pathogen burden and risk of myocardial infarction or death.
      • Chiu B
      Multiple infections in carotid atherosclerotic plaques.
      Until well-designed and powered ongoing studies of long-term treatment prove a significant benefit, antibiotic treatment of patients with acute or chronic CAD cannot be recommended.

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