Antibiotics in acute and chronic coronary syndromes.
Tryfon Vainas, MD and Saiqa Sayed, MBChB, MRCS1
Dept of Surgery, Maastricht University Hospital, Maastricht, The Netherlands and 1Department of Vascular Surgery, St George’s Hospital Medical School, London, UK
The first hint that chlamydial infections may be related to arterial disease stems from the observation in the early 1940’s that patients with cardiovascular disease and no history of lymphogranuloma venereum often demonstrated a positive intradermal Frei test, a test used to measure hypersensitivity to all chlamydial species. 1-3 Saikku and colleagues demonstrated in 1988 that Chlamydia pneumoniae serology is associated with stable and acute coronary phenomena.4 Since this time evidence has gathered to suggest that Chlamydia pneumoniae infections play a (modulatory) role in the development of atherosclerosis.5 The interest in the potential role of Chlamydia pneumoniae in cardiovascular disease was intensified by two independent reports which showed that prophylactic antibiotic treatment of patients with coronary artery disease may reduce the incidence of cardiovascular events.6,7 This remarkable finding prompted the initiation and publication of a great number of retrospective and prospective studies that explored the anti-atherogenic properties of antichlamydial antibiotics and that often demonstrated contradictory results. Recently the New England Journal of Medicine published the results of two mega-trials adding solid level 1 evidence to the discussion of whether antibiotics contribute to secondary prevention in cardiovascular disease.8,9
Linking Chlamydia pneumoniae to atherosclerosis
Chlamydia pneumoniae serology has been associated with all manifestations of atherosclerotic disease (i.e., coronary artery disease, cerebrovascular disease, peripheral arterial disease and aneurysm disease), and Chlamydia pneumoniae traces (DNA and/or proteins) have been detected in atherosclerotic plaques throughout the vascular tree.10 It is believed that Chlamydia pneumoniae reaches the vasculature through infected alveolar monocytes/macrophages after a respiratory tract infection.11 The bacterium has shown to infect all cells of the vascular wall, i.e. endothelial cells, monocytes/macrophages and smooth muscle cells,12 inducing pro-atherogenic phenomena such as foam cell formation, 13 lipoprotein oxidation, 14,15 secretion of inflammatory molecules, 16-19 endothelial hypercoagulability,20,21 and smooth muscle cell proliferation.22 In addition, the association between infection and atherosclerosis may be mediated by the systemic effects of (non) vascular Chlamydia pneumoniae infection or by the host response to Chlamydial infection. In this context we have shown Chlamydia pneumoniae serology is associated with hypercoagulability rather than histological atherosclerotic plaque instability.23 This conforms with the finding that in patients with Chlamydia pneumoniae infections, plasma fibrinogen levels are elevated, and that these levels decrease upon anti-microbial treatment. Furthermore, the systemic pro-atherogenic effects of Chlamydia pneumoniae infection may result from induction and/or maintenance of an inflammatory response characterized by chronically elevated pro-inflammatory cytokine levels and increased gelatinolytic activity, or may alternatively result from induction of an autoimmune reaction based on antigenic mimicry between chlamydial and human heat shock protein 60.24,25 Animals studies have shown that Chlamydia pneumoniae induces experimental atherosclerosis that can be prevented by antibiotics.26 Repeated inoculations and a hyperlipidemic background are prerequisites for the demonstration of the atherogenic properties of Chlamydia pneumoniae infection in animal models. In these models, the Chlamydia pneumoniae related atherosclerosis progression can only be prevented by antibiotics when they are administered within 5 days of inoculation of the animals.27
The sero-epidemiological and experimental data showing the possible association between Chamydia pneumoniae infection and atherosclerosis triggered the interest of (cardio)vascular clinicians for the role of anti-chlamydial antibiotics as a new treatment modality for patients with atherosclerotic vascular disease. Indeed, two early small randomised clinical trials suggested that antibiotics may reduce cardiovascular risk in patients with coronary artery disease.6,7
Antibiotics in atherosclerotic disease
Several investigators have tried to evaluate the effect of antibiotics on cardiovascular risk by observational case-control studies. A number of these studies demonstrated a survival benefit from exposure to anti-chlamydial antibiotics,28-31 although others refuted it.32-36 Considering the methodological shortcomings of these studies, randomised clinical trials were needed to determine the effectiveness of antibiotics in atherosclerotic disease prevention. Following the two initial positive pilot studies6,7 a number of antibiotic trials have been designed and carried out worldwide with contradictory results.8,9,37-55 In general, favourable results were shown in studies with small sample size and/or limited follow up,6,7,44,45,56 trials that have included patients with abdominal aortic aneurysms42,43 or studied surrogate endpoints such as carotid intima media thickness,56 basal NO production,37 flow mediated dilatation,47,52 aortic expansion rate42,43 and matrix metalloproteinase metabolism.48 Recent larger studies, involving patients with coronary artery disease8,9,49-51 or peripheral arterial disease55, demonstrated no beneficial effect of antibiotics in the prevention of cardiovascular events or death.
The table lists all the randomised clinical trials carried out to assess the effects of antibiotics on cardiovascular endpoints in patients with atherosclerotic disease of the coronary, cerebral and/or peripheral circulation. Overall these data suggest that antibiotics are not able to reduce cardiovascular risk in atherosclerotic patients. More than 21.000 patients were randomised to an antibiotic or placebo. The studies reporting beneficial effects of antibiotics on cardiovascular risk reduction have included 1583 patients, and 858 of these were randomised to receive the experimental treatment. In contrast 19.693 were included and 9.842 were randomised to receive an antibiotic in the negative trials.
Despite this convincing evidence for a lack of effect of antibiotics on cardiovascular risk, several critical issues should be highlighted. A methodological limitation of all Chlamydia pneumoniae related cardiovascular studies is the inability to select patients with clinically relevant (vascular) Chlamydia pneumoniae infection. In general, Chlamydia pneumoniae IgA or IgG antibody titres are not related to presence of Chlamydia pneumoniae in the vascular tissue, 57-59 whereas high antibody titers are related to the development of cardiovascular events. Despite the numerous sero-epidemiological studies showing a relation between Chlamydia serology and cardiovascular events,60 no consensus has been reached regarding the serological detection of chronic active or persistent Chlamydia pneumoniae infection.61 Antibiotics have shown no effect on Chlamydia pneumoniae titers in cardiovascular patients.42,44,53,62,63 Furthermore, the lack of any effect of antibiotics on cardiovascular risk reduction was observed, both, in studies that included only patients with Chlamydia pneumoniae antibodies39,49 as well as in studies that included patients regardless of their serological status.8,9,50,51,54,55,62
Inadequate study medication may also have influenced the results of the antibiotic intervention trials. Although, all the studied antibiotics (azithromycine, clarithromycin, roxithromycin, and gatifloxacin) have proven antichlamydial properties, it is likely that other microbes such as helicobacter pylori,64 cytomegalovirus65 and herpes simplex virus66 that are not sensitive for the studied drugs may also have pro-atherogenic properties. In fact, it seems that the total pathogen burden more than an individual micro-organism is associated with cardiovascular risk.67,68 Other antibiotic related variables such as dosage and treatment-duration may have also affected the results. Published data suggest that the possible effect of antibiotics on risk reduction may decline with time. A preliminary report of the ROXIS trial showed a significant reduction of the primary endpoint (cardiac ischaemic death, myocardial infarction, and severe recurrent ischaemia) by roxithromycin at 31 days7 whereas this effect had worn off at 6 months.62 Similarly, roxithromycin seemed to reduce intima-media thickness progression in patients with cerebrovascular disease during the first 2 years after treatment, however this effect was lost after 4 years.53 A temporary effect of antibiotic treatment has also been suggested by the data of the WIZARD trial. The results of this trial showed a reduced risk of death or myocardial infarction at 6 months after randomisation but not after a longer follow up.49 Antibiotics may have only a transient effect, as patients may contract recurrent Chlamydia pneumoniae infections or suffer from Chlamydia pneumoniae reactivation, after the microbe has been forced into a latent state instead of being eliminated by the antibiotic treatment. In fact, effective treatment of chronic (vascular) Chlamydia pneumoniae infection may be more troublesome than initially anticipated. Recent in vitro evidence suggests that Chlamydia pneumoniae carried within macrophages is refractory to anti-chlamydial antibiotics69 and that even prolonged antibiotic treatment failed to completely eliminate Chlamydia pneumoniae from infected epithelial cells.70 It may therefore not be surprising that the prolonged treatment strategies, varying from 3 to 24 months, employed in the recently published mega-trials have not resulted in a significant reduction of cardiovascular events.8,9,49 Considering the fact that in animals the Chlamydia pneumoniae related progression of atherosclerosis can only be prevented by antibiotics when they are administered within 5 days of inoculation of the animals, and that in humans the majority of Chlamydia pneumoniae respiratory tract infections remain clinically unnoticed whereas Chlamydia pneumoniae antibody titers rise already during early childhood, it might be concluded that antibiotics may only contribute to cardiovascular risk reduction when administered early in life as part of a primary preventive strategy.
Cardiovascular events are the result of various vascular biological phenomena, such as atherosclerotic plaque growth and rupture, (neo)intimal hyperplasia after bypass grafting or angioplasty, and thrombosis. In contrast to cardiovascular survival, antibiotics may protect against aneurysm expansion rate42,43 and restenosis after coronary stent placement.41 The few trials assessing the effect of antibiotic treatment on these outcome criteria have shown positive results, but have small sample sizes and should therefore be verified by more data before definitive conclusions can be drawn.
To conclude it would appear that antibiotics do not offer any (cardiovascular) survival benefits in patients with atherosclerotic disease. Nevertheless, the limited data available suggest that anti-chlamydial antibiotics may have beneficial effects on two vascular biological processes, i.e. aortic aneurysm expansion rate42,43 and post-stent intimal hyperplasia and restenosis.41 The clinical relevance of aneurysm expansion and restenosis after stenting or bypass grafting warrants further investigations into the role of infections and antibiotics in these phenomena.
1. May J. La intradermoreaccion de Frei en las arteriopatias. Revista Argentina Dermatosifilis. 1943;27:581-2.
2. Quiroga M, Ambrosetti FE. La reaccion de Frei en las endoarteritis obliterantes. Revista Argentina Dermatosifilis. 1943;27:624-5.
3. Coutts WE, Davila M. Lymphogranuloma venereum as a possible cause of arteriosclerosis and other arterial conditions. J Trop Med Hyg. 1945;48:46-51.
4. Saikku P, Leinonen M, Mattila K, Ekman MR, Nieminen MS, Makela PH, Huttunen JK, Valtonen V. Serological evidence of an association of a novel Chlamydia, TWAR, with chronic coronary heart disease and acute myocardial infarction. Lancet. 1988;2:983-6.
5. Campbell LA, Kuo CC. Chlamydia pneumoniae—an infectious risk factor for atherosclerosis? Nat Rev Microbiol. 2004;2:23-32.
6. 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. Circulation. 1997;96:404-7.
7. Gurfinkel E, Bozovich G, Daroca A, Beck E, Mautner B. Randomised trial of roxithromycin in non-Q-wave coronary syndromes: ROXIS Pilot Study. ROXIS Study Group. Lancet. 1997;350:404-7.
8. Cannon CP, Braunwald E, McCabe CH, Grayston JT, Muhlestein B, Giugliano RP, Cairns R, Skene AM. Antibiotic treatment of Chlamydia pneumoniae after acute coronary syndrome. N Engl J Med. 2005;352:1646-54.
9. Grayston JT, Kronmal RA, Jackson LA, Parisi AF, Muhlestein JB, Cohen JD, Rogers WJ, Crouse JR, Borrowdale SL, Schron E, Knirsch C. Azithromycin for the secondary prevention of coronary events. N Engl J Med. 2005;352:1637-45.
10. Leinonen M, Saikku P. Evidence for infectious agents in cardiovascular disease and atherosclerosis. Lancet Infect Dis. 2002;2:11-7.
11. Moazed TC, Kuo C, Grayston JT, Campbell LA. Murine models of Chlamydia pneumoniae infection and atherosclerosis. J Infect Dis. 1997;175:883-90.
12. Gaydos CA, Summersgill JT, Sahney NN, Ramirez JA, Quinn TC. Replication of Chlamydia pneumoniae in vitro in human macrophages, endothelial cells, and aortic artery smooth muscle cells. Infect Immun. 1996;64:1614-20.
13. Kalayoglu MV, Byrne GI. Induction of macrophage foam cell formation by Chlamydia pneumoniae. J Infect Dis. 1998;177:725-9.
14. Kalayoglu MV, Hoerneman B, LaVerda D, Morrison SG, Morrison RP, Byrne GI. Cellular oxidation of low-density lipoprotein by Chlamydia pneumoniae. J Infect Dis. 1999;180:780-90.
15. 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. J Infect Dis. 2000;181 Suppl 3:S483-9.
16. Kaukoranta-Tolvanen SS, Teppo AM, Laitinen K, Saikku P, Linnavuori K, Leinonen M. Growth of Chlamydia pneumoniae in cultured human peripheral blood mononuclear cells and induction of a cytokine response. Microb Pathog. 1996;21:215-21.
17. Netea MG, Selzman CH, Kullberg BJ, Galama JM, Weinberg A, Stalenhoef AF, Van der Meer JW, Dinarello CA. Acellular components of Chlamydia pneumoniae stimulate cytokine production in human blood mononuclear cells. Eur J Immunol. 2000;30:541-9.
18.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. Circulation. 1998;98:300-7.
19. Vehmaan-Kreula P, Puolakkainen M, Sarvas M, Welgus HG, Kovanen PT. Chlamydia pneumoniae proteins induce secretion of the 92-kDa gelatinase by human monocyte- derived macrophages. Arterioscler Thromb Vasc Biol. 2001;21:E1-8.
20. Fryer RH, Schwobe EP, Woods ML, Rodgers GM. Chlamydia species infect human vascular endothelial cells and induce procoagulant activity. J Investig Med. 1997;45:168-74.
21. Dechend R, Maass M, Gieffers J, Dietz R, Scheidereit C, Leutz A, Gulba DC. 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. Circulation. 1999;100:1369-73.
22. Coombes BK, Mahony JB. Chlamydia pneumoniae infection of human endothelial cells induces proliferation of smooth muscle cells via an endothelial cell-derived soluble factor(s). Infect Immun. 1999;67:2909-15.
23. Vainas T, Kurvers HA, Mess WH, de Graaf R, Ezzahiri R, Tordoir JH, Schurink GW, Bruggeman CA, Kitslaar PJ. Chlamydia pneumoniae serology is associated with thrombosis-related but not with plaque-related microembolization during carotid endarterectomy. Stroke. 2002;33:1249-54.
24. Mayr M, Metzler B, Kiechl S, Willeit J, Schett G, Xu Q, Wick G. Endothelial cytotoxicity mediated by serum antibodies to heat shock proteins of Escherichia coli and Chlamydia pneumoniae: immune reactions to heat shock proteins as a possible link between infection and atherosclerosis. Circulation. 1999;99:1560-6.
25. Wick G, Knoflach M, Xu Q. Autoimmune and inflammatory mechanisms in atherosclerosis. Annu Rev Immunol. 2004;22:361-403.
26. Muhlestein JB, Anderson JL, Hammond EH, Zhao L, Trehan S, Schwobe EP, Carlquist JF. Infection with Chlamydia pneumoniae accelerates the development of atherosclerosis and treatment with azithromycin prevents it in a rabbit model. Circulation. 1998;97:633-6.
27. Fong IW. Antibiotics effects in a rabbit model of Chlamydia pneumoniae-induced atherosclerosis. J Infect Dis. 2000;181 Suppl 3:S514-8.
28. Meier CR, Derby LE, Jick SS, Vasilakis C, Jick H. Antibiotics and risk of subsequent first-time acute myocardial infarction. Jama. 1999;281:427-31.
29. Herings RM, Leufkens HG, Vandenbroucke JP. Acute myocardial infarction and prior antibiotic use. Jama. 2000;284:2998-9.
30. Ostergaard L, Sorensen HT, Lindholt J, Sorensen TE, Pedersen L, Eriksen T, Andersen PL. Risk of hospitalization for cardiovascular disease after use of macrolides and penicillins: a comparative prospective cohort study. J Infect Dis. 2001;183:1625-30.
31. Pilote L, Green L, Joseph L, Richard H, Eisenberg MJ. Antibiotics against Chlamydia pneumoniae and prognosis after acute myocardial infarction. Am Heart J. 2002;143:294-300.
32. Jackson LA, Smith NL, Heckbert SR, Grayston JT, Siscovick DS, Psaty BM. Lack of association between first myocardial infarction and past use of erythromycin, tetracycline, or doxycycline. Emerg Infect Dis. 1999;5:281-4.
33. Luchsinger JA, Pablos-Mendez A, Knirsch C, Rabinowitz D, Shea S. Antibiotic use and risk of ischemic stroke in the elderly. Am J Med. 2001;111:361-6.
34. Luchsinger JA, Pablos-Mendez A, Knirsch C, Rabinowitz D, Shea S. Relation of antibiotic use to risk of myocardial infarction in the general population. Am J Cardiol. 2002;89:18-21.
35.Brassard P, Bourgault C, Brophy J, Kezouh A, Suissa S. Antibiotics in primary prevention of stroke in the elderly. Stroke. 2003;34:e163-6.
36 Brassard P, Bourgault C, Brophy J, Kezouh A, Rainville B, Xhignesse M, Suissa S. Antibiotics in primary prevention of myocardial infarction among elderly patients with hypertension. Am Heart J. 2003;145:E20.
37. Sinisalo J, Mattila K, Nieminen MS, Valtonen V, Syrjala M, Sundberg S, Saikku P. The effect of prolonged doxycycline therapy on Chlamydia pneumoniae serological markers, coronary heart disease risk factors and forearm basal nitric oxide production. J Antimicrob Chemother. 1998;41:85-92.
38. Melissano G, Blasi F, Esposito G, Tarsia P, Dordoni L, Arosio C, Tshomba Y, Fagetti L, Allegra L, Chiesa R. Chlamydia pneumoniae eradication from carotid plaques. Results of an open, randomised treatment study. Eur J Vasc Endovasc Surg. 1999;18:355-9.
39. Muhlestein JB, Anderson JL, Carlquist JF, Salunkhe K, Horne BD, Pearson RR, Bunch TJ, Allen A, Trehan S, Nielson C. Randomized secondary prevention trial of azithromycin in patients with coronary artery disease: primary clinical results of the ACADEMIC study. Circulation. 2000;102:1755-60.
40.Jackson LA. Description and status of the azithromycin and coronary events study (ACES). J Infect Dis. 2000;181 Suppl 3:S579-81.
41. Neumann F, Kastrati A, Miethke T, Pogatsa-Murray G, Mehilli J, Valina C, Jogethaei N, da Costa CP, Wagner H, Schomig A. Treatment of Chlamydia pneumoniae infection with roxithromycin and effect on neointima proliferation after coronary stent placement (ISAR- 3): a randomised, double-blind, placebo-controlled trial. Lancet. 2001;357:2085-9.
42. Mosorin M, Juvonen J, Biancari F, Satta J, Surcel HM, Leinonen M, Saikku P, Juvonen T. Use of doxycycline to decrease the growth rate of abdominal aortic aneurysms: A randomized, double-blind, placebo-controlled pilot study. J Vasc Surg. 2001;34:606-10.
43. Vammen S, Lindholt JS, Ostergaard L, Fasting H, Henneberg EW. Randomized double-blind controlled trial of roxithromycin for prevention of abdominal aortic aneurysm expansion. Br J Surg. 2001;88:1066-72.
44. Stone AF, Mendall MA, Kaski JC, Edger TM, Risley P, Poloniecki J, Camm AJ, Northfield TC. 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). Circulation. 2002;106:1219-23.
45. Sinisalo J, Mattila K, Valtonen V, Anttonen O, Juvonen J, Melin J, Vuorinen-Markkola H, Nieminen MS. Effect of 3 months of antimicrobial treatment with clarithromycin in acute non-q-wave coronary syndrome. Circulation. 2002;105:1555-60.
46. Wiesli P, Czerwenka W, Meniconi A, Maly FE, Hoffmann U, Vetter W, Schulthess G. Roxithromycin treatment prevents progression of peripheral arterial occlusive disease in Chlamydia pneumoniae seropositive men: a randomized, double-blind, placebo-controlled trial. Circulation. 2002;105:2646-52.
47. 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. Circulation. 2002;105:1298-303.
48. Axisa B, Loftus IM, Naylor AR, Goodall S, Jones L, Bell PR, Thompson MM. Prospective, randomized, double-blind trial investigating the effect of doxycycline on matrix metalloproteinase expression within atherosclerotic carotid plaques. Stroke. 2002;33:2858-64.
49. O’Connor CM, Dunne MW, Pfeffer MA, Muhlestein JB, Yao L, Gupta S, Benner RJ, Fisher MR, Cook TD. Azithromycin for the secondary prevention of coronary heart disease events: the WIZARD study: a randomized controlled trial. Jama. 2003;290:1459-66.
50. Zahn R, Schneider S, Frilling B, Seidl K, Tebbe U, Weber M, Gottwik M, Altmann E, Seidel F, Rox J, Hoffler U, Neuhaus K-L, Senges J, for the Arbeitsgemeinschaft Leitender Kardiologischer Krankenhausarzte (Working Group of Leading Hospital Cardiologists; ALKK). Antibiotic Therapy After Acute Myocardial Infarction: A Prospective Randomized Study. Circulation. 2003;107:1253-1259.
51. Cercek B, Shah PK, Noc M, Zahger D, Zeymer U, Matetzky S, Maurer G, Mahrer P. Effect of short-term treatment with azithromycin on recurrent ischaemic events in patients with acute coronary syndrome in the Azithromycin in Acute Coronary Syndrome (AZACS) trial: a randomised controlled trial. Lancet. 2003;361:809-13.
52. Kuvin JT, Gokce N, Holbrook M, Hunter LM, Patel AR, Sliney KA, Craven DE, Grayston JT, Keaney JF, Jr., Karas RH, Vita JA. Effect of short-term antibiotic treatment on Chlamydia pneumoniae and peripheral endothelial function. Am J Cardiol. 2003;91:732-5.
53. Sander D, Winbeck K, Klingelhofer J, Etgen T, Conrad B. Progression of early carotid atherosclerosis is only temporarily reduced after antibiotic treatment of Chlamydia pneumoniae seropositivity. Circulation. 2004;109:1010-5.
54. Berg HF, Maraha B, Scheffer GJ, Quarles-van Ufford M, Vandenbroucke-Grauls CM, Peeters MF, Kluytmans JA. Treatment with clarithromycin prior to coronary artery bypass graft surgery does not prevent subsequent cardiac events. Clin Infect Dis. 2005;40:358-65.
55. Vainas T, Stassen FR, Schurink GW, Tordoir JH, Welten RJ, van den Akker LH, Kurvers HA, Bruggeman CA, Kitslaar PJ. Secondary Prevention of Atherosclerosis Through Chlamydia pneumoniae Eradication (SPACE Trial): A Randomised Clinical Trial in Patients with Peripheral Arterial Disease. Eur J Vasc Endovasc Surg. 2005;29:403-11.
56. Sander D, Winbeck K, Klingelhofer J, Etgen T, Conrad B. Reduced progression of early carotid atherosclerosis after antibiotic treatment and Chlamydia pneumoniae seropositivity. Circulation. 2002;106:2428-33.
57. Bartels C, Maass M, Bein G, Brill N, Bechtel JF, Leyh R, Sievers HH. Association of serology with the endovascular presence of Chlamydia pneumoniae and cytomegalovirus in coronary artery and vein graft disease. Circulation. 2000;101:137-41.
58. Maass M, Gieffers J, Krause E, Engel PM, Bartels C, Solbach W. Poor correlation between microimmunofluorescence serology and polymerase chain reaction for detection of vascular Chlamydia pneumoniae infection in coronary artery disease patients. Med Microbiol Immunol (Berl). 1998;187:103-6.
59. Porqueddu M, Spirito R, Parolari A, Zanobini M, Pompilio G, Polvani G, Alamanni F, Stangalini D, Tremoli E, Biglioli P. Lack of association between serum immunoreactivity and Chlamydia pneumoniae detection in the human aortic wall. Circulation. 2002;106:2647-8.
60. Bloemenkamp DG, Mali WP, Visseren FL, van der Graaf Y. Meta-analysis of sero-epidemiologic studies of the relation between Chlamydia pneumoniae and atherosclerosis: does study design influence results? Am Heart J. 2003;145:409-17.
61. Dowell SF, Peeling RW, Boman J, Carlone GM, Fields BS, Guarner J, Hammerschlag MR, Jackson LA, Kuo CC, Maass M, Messmer TO, Talkington DF, Tondella ML, Zaki SR. Standardizing Chlamydia pneumoniae assays: recommendations from the Centers for Disease Control and Prevention (USA) and the Laboratory Centre for Disease Control (Canada). Clin Infect Dis. 2001;33:492-503.
62. 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. Eur Heart J. 1999;20:121-7.
63. 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 [In Process Citation]. J Antimicrob Chemother. 1999;44:411-4.
64. Aceti A, Mazzacurati G, Amendolea M, Pennica A, Zechini B, Trappolini M, Puletti M. Relation of C reactive protein to cardiovascular risk factors. H pylori and C pneumoniae infections may account for most acute coronary syndromes. BMJ. 1996;313:428-9.
65. Adam E, Melnick JL, Probtsfield JL, Petrie BL, Burek J, Bailey KR, McCollum CH, DeBakey ME. High levels of cytomegalovirus antibody in patients requiring vascular surgery for atherosclerosis. Lancet. 1987;2:291-3.
66. Siscovick DS, Schwartz SM, Corey L, Grayston JT, Ashley R, Wang SP, Psaty BM, Tracy RP, Kuller LH, Kronmal RA. Chlamydia pneumoniae, herpes simplex virus type 1, and cytomegalovirus and incident myocardial infarction and coronary heart disease death in older adults : the cardiovascular health study. Circulation. 2000;102:2335-40.
67. Bloemenkamp DG, Mali WP, Tanis BC, Rosendaal FR, van den Bosch MA, Kemmeren JM, Algra A, Ossewaarde JM, Visseren FL, van Loon AM, van der Graaf Y. Chlamydia pneumoniae, Helicobacter pylori and cytomegalovirus infections and the risk of peripheral arterial disease in young women. Atherosclerosis. 2002;163:149-56.
68. Espinola-Klein C, Rupprecht HJ, Blankenberg S, Bickel C, Kopp H, Rippin G, Victor A, Hafner G, Schlumberger W, Meyer J. Impact of infectious burden on extent and long-term prognosis of atherosclerosis. Circulation. 2002;105:15-21.
69. Gieffers J, Fullgraf H, Jahn J, Klinger M, Dalhoff K, Katus HA, Solbach W, Maass M. Chlamydia pneumoniae infection in circulating human monocytes is refractory to antibiotic treatment. Circulation. 2001;103:351-6.
70. Kutlin A, Roblin PM, Hammerschlag MR. Effect of Prolonged Treatment with Azithromycin, Clarithromycin, or Levofloxacin on Chlamydia pneumoniae in a Continuous-Infection Model. Antimicrob Agents Chemother. 2002;46:409-12.