Asian Cardiovasc Thorac Ann 2007;15:9-13
© 2007 Asia Publishing EXchange Ltd
Is Chlamydia Pneumoniae a Risk Factor for Peripheral Atherosclerosis?
Ha
im Üstünsoy, MD,
Cumhur Sivrikoz, MD1,
Fatma Sirmatel, MD2,
Kemal Bakir, MD3,
Oktay Burma, MD4,
Hakki Kazaz, MD
Department of Cardiovascular Surgery
2 Department of Infectious Disease and Clinical Microbiology
3 Department of Pathology, Gaziantep University Medical Faculty, Gaziantep, Turkey
1 Department of Thoracic Surgery, Osmangazi University Medical Faculty, Eskiehir, Turkey
4 Department of Cardiovascular Surgery, Firat University, Elazig, Turkey
For reprint information contact: Haim Üstünsoy, MD, Tel: 90 342 360 3910, Fax: 90 342 360 0196, Email: hustunsoy{at}yahoo.com, Gaziantep University Medical Faculty, Department of Cardiovascular Surgery, Bulvari University, Gaziantep 27310, Turkey.
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ABSTRACT
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Seroepidemiological studies have shown a relationship between Chlamydia pneumoniae and coronary atherosclerosis. It is not clear whether Chlamydia pneumoniae is also a risk factor for peripheral atherosclerosis. Chlamydia pneumoniae antibodies were measured by a microimmunofluorescence method in 75 patients who underwent surgery for peripheral atherosclerosis, and the seroprevalence was compared with that in the normal population. Chlamydia pneumoniae immunoglobulin-G seroprevalence was 80% in the study group vs. 40% in controls. More foam cells were noted on light microscopy in atherosclerotic plaques from the infected patients. The 60 infected patients were divided into: group A (n = 35) given both anti-chlamydial and antiplatelet agents for 1 year; and group B (n = 25) given antiplatelet therapy only. The groups were compared on the basis of clinical findings, ankle-brachial index, and antibody titers. Decreasing Chlamydia pneumoniae immunoglobulin-G seroprevalence in group A correlated significantly with increasing ankle-brachial index and improvement in clinical findings. It was concluded that Chlamydia pneumoniae may be a risk factor for peripheral atherosclerosis.
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INTRODUCTION
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The effect of Chlamydia pneumoniae (Cp) on the development of atherosclerosis has been widely investigated in the last 10 years.1,2 Some studies found Cp to be a risk factor for coronary atherosclerosis and acute myocardial infarction.3,4 It is not clear whether Cp is also a risk factor for atherosclerotic peripheral vascular disease (PVD). The main aims of this study were to evaluate Cp as a risk factor for PVD and to determine the effects of antibiotic therapy on PVD.
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PATIENTS AND METHODS
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Between July 1999 and August 2002, immunoglobulin (Ig) -G, -A, and -M antibodies to Cp were studied in patients undergoing vascular bypass surgery for peripheral atherosclerotic lesions. Only patients with bypasses constructed above the knee were included in the study because the success rates of the surgical procedures are similar, and there are no procedural effects on the clinical outcome. The definition of atherosclerotic PVD was a reliable description of claudication in one or both legs, ischemic pain at rest, diminished or absent femoral or distal pulses on physical examination, shiny atrophic skin in the distal limb or feet, decreased temperature, marked rubor, areas of ulceration, ischemic necrosis or gangrene, decreased ankle-brachial index (< 75%), and more than 50% stenosis on aortoiliac, femoral, or popliteal digital subtraction angiography. Patients who had used macrolides or tetracycline in the previous 2 months and those with a history of cardiac or peripheral vascular surgery, myocardial infarction, or stroke were excluded from the study. Seventy-five patients were enrolled in the study; all were Turkish and had lived exclusively in Southeast Turkey. Their mean age was 48.36 ± 17.41 years, with a range of 24–72 years. The ratio of males to females was 1:3. Risk factors for PVD are listed in Table 1
. All patients were operated on by the same surgical team, using saphenous vein grafts in 67 and polytetrafluoroethylene (PTFE) grafts in 8. Four of the PTFE grafts were used in patients with Leriche syndrome, and 4 were used for femoropopliteal bypass because the saphenous vein was unsuitable due to thrombophlebitis. All anastomoses were performed with polypropylene suture. The locations of the lesions are shown in Table 2.
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Table 2. Locations of Atherosclerotic Lesions in Antibiotic/Aspirin-Treated (group A), Aspirin-only (group B), and Noninfected Patients
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The IgG, IgA, and IgM antibodies to Cp were analyzed in each patient in the 1st, 3rd, and 12th month postoperatively, using a microimmunofluorescence test kit (Orgenium Laboratories, Helsinki, Finland), in a blinded fashion. High-density lipoprotein, very high-density lipoprotein, and total lipids were also analyzed. Atherosclerotic plaques containing foam cells, which were obtained perioperatively from 60 patients with Cp infection and 15 noninfected patients were also observed and compared in a blinded pathologic study using light microscopy with hematoxylin and eosin. The 60 Cp-infected patients were randomly divided into 2 groups. Randomization was achieved with a randomization table. The 35 patients in group A were treated with both antibiotic and antiplatelet agents. The 25 patients in group B were treated with antiplatelet agents only. The number of patients in group A was higher so as to determine the effect of antibiotic therapy more precisely. The risk factors for PVD in both groups of infected patients were similar (Table 3). In group A, a macrolide antibiotic (azithromycin 1g daily for the first 3 days and then 500 mg weekly for one year) was added to the antiplatelet therapy (aspirin 150 mg daily). In group B, only oral aspirin (150 mg daily) was given.
The groups were compared on the basis of clinical findings, ankle-brachial index (ABI), and Cp seroprevalence tests that were performed in the 1st, 3rd, and 12th month. The Wilcoxon rank sum test was used to compare IgG seroprevalence in the study group and the normal healthy population, as well as between groups A and B. A value of p < 0.05 was considered to be significant.
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RESULTS
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All Cp IgG antibody titers > 1/512 were accepted as positive for infection. Positive Cp seroprevalence (IgG titer > 1/32) was found in 60 patients (80%) whereas the normal population from the same district of Turkey has a Cp seroprevalence of 29.9% to 56.3% (mean, 40%), which was statistically significant ( p > 0.05). Five Cp IgA was positive only in a few patients (titer > 1/32), and Cp IgM titers were negative in all patients. After 3 months, a decrease in Cp IgG seroprevalence correlated with an increase in ABI and improvement in clinical findings in group A (Figure 1). The decrease of seroprevalence in group A was also found to be significant ( p < 0.005).
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Figure 1. Plasma levels of Chlamydia pneumoniae immunoglobulin-G (IgG) antibody in patients with peripheral atherosclerosis at baseline and after 3 and 12 months of treatment.
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After the first surgical intervention, repeat thrombectomies were performed in 5 infected patients. One graft failure occurred in the non-infected patients due to bad run-off. Chlamydia pneumoniae IgG levels in repeat thrombectomy patients were higher than those in the other infected patients. The mean IgG titer in these patients was 1/476, whereas it was 1/256 in infected patients. Due to insufficient numbers, the results were not compared statistically. Therefore, we suggest that Cp may be a risk factor in acute thrombosis of the atherosclerotic lesions, and this warrants further investigation. No difference was found in other atherosclerotic risk factors among the groups (Table 1
). High-density lipoprotein levels of the infected group were lower than those of the non-infected group, whereas the very high-density lipoprotein levels of the infected group were higher than the non-infected group. The levels of both parameters were measured after antibiotic therapy without any anti-lipid drug usage.
Although the ABI of both groups was the same in the early postoperative period and during the first test, the ABI of group A was better than group B in the second test. These differences did not reach statistical significance (Table 4). The Wilcoxon rank sum test was performed on the data for ABI in each group at 1 and 12 months postoperatively. In group A, there was a significant increase in ABI at 12 months ( p = 0.0008, Z = 4.433). In group B, the increase was limited ( p = 0.0318, Z = 2.151). There was a difference between the rise in ABI in both groups, with the rise in group A being significantly higher ( p = 0.0164, Z = 2.419). On light microscopy, the amount of foam cells in patients with Cp infection was much more than in noninfected patients. Every microscopic area was characterized by 2%–3% foam cells in the noninfected patients (Figure 2), whereas it was 50% in the infected patients (Figure 3).
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Figure 2. Light microscopic view of foam cells in the atherosclerotic plaque of a noninfected patient. The arrow indicates a foam cell. Hematoxylin and eosin stain, original magnification x 200.
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Figure 3. Light microscopic view of foam cells in the atherosclerotic plaque of a patient with Chlamydia pneumoniae infection. Thin arrow indicates foam cell nucleus, thick arrow indicates foam cell cytoplasm. Hematoxylin and eosin stain, original magnification x 200.
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DISCUSSION
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The pathophysiologic classification of vascular injury or damage is divided into three types: type I consists of functional alterations of endothelial cells without substantial morphologic changes; type II is endothelial denudation and intimal damage with intact internal elastic lamina; and type III is endothelial denudation with damage to both the intima and media.1,6 Tears in the atherosclerotic plaque, bleeding into the plaque, and fibromuscular hypertrophy cause acute thrombosis and distal embolization.6 Autopsies are negative for atherosclerotic plaques in the 1st decade of life, whereas they are common in the 2nd and 3rd decades due to the progression of risk factors.1 Many risk factors, such as hypertension, diabetes mellitus, smoking, race, sex, hypercholesterolemia, and hyperlipidemia, have been identified.1–3,7 Recently, Cp has been reported as a risk factor for atherosclerosis (especially coronary disease).4,7,8
Chlamydia pneumoniae causes upper and lower respiratory infections including more than 10% of cases of otitis media, pharyngitis, bronchitis, and pneumonia. Many infections may be asymptomatic or subclinical.8 Chlamydia pneumoniae has also been described as a cause of endocarditis and myocarditis.9 It invades endothelial cells and mononuclear lymphocytes where it is converted into a noninfective reticulate body.9 In vitro studies have shown that Cp may also survive and multiply in endothelial cells and macrophages.4 These studies indicate that macrophages may be a reservoir for chronic infection.2,4 Recently, it has been shown that Cp induces production of interleukin-l by human monocytes. Interleukin-l is known to induce production of collagenase and collagen, with the stimulation of fibroblast and smooth muscle cell proliferation.4 It also causes lipid accumulation in macrophages and may increase low-density lipoprotein and decrease high-density lipoprotein, causing increased foam cell formation in the endothelium.8,10 We found increased amounts of foam cells in atherosclerotic plaques of Cp-infected patients. Increased low-density lipoprotein and decreased high-density lipoprotein levels were also observed in the infected patients. Both levels responded to antibiotic therapy in group A: low-density lipoprotein levels decreased, and high-density lipoprotein levels increased. The release of toxic products such as tissue matrix metalloproteins by macrophages may lead to tearing or ulceration of the fibrous capsule of the atherosclerotic plaque, which may result in acute thrombus or distal embolization.11,12 We performed 5 repeat thrombectomies in our infected patients with high Cp IgG titers. All of these factors could explain the association between Cp and atherosclerotic-thrombotic disease.
Shor and colleagues13 also demonstrated a Cp-like organism in coronary atherosclerotic plaques by electron microscopy and polymerase chain reaction, and Cp-specific antigens on immunoperoxidase staining. Infection with Cp is endemic, but epidemic infection may occur every 2–3 years, followed by 3–10 years with a lower incidence.8 Infants are seldom infected. The infection arises in pre-school children and young adolescents, and increases with age.4 The mean age of our study population was young (48.36 years). The range may seem large, but all diagnoses were confirmed from the pathological specimens. In this region of Turkey, the prevalence of diabetes and metabolic syndrome is very high, especially in females, and the incidence of peripheral atherosclerosis in females is high. Immunoglobulin-G and IgA antibody titers usually decline and disappear 3–6 months after infection.4 A chronic infection may be indicated if the IgA level is persistently high. Immunoglobulin-G antibody titers may persist for years, thus they are meaningful in the diagnosis of chronic infection. In our study, Cp IgG seroprevalence was 80% in the atherosclerotic patients and 40% in the normal population.5,14
Although serology performed with immunoperoxidase is simple and easy, the PCR method is more important and reliable for detecting Cp infection in atherosclerotic patients in developing countries.8 Antibiotic treatment with antiplatelet therapy may help surgery and prevent re-operations due to atherosclerotic progression.8 Tetracycline, macrolide, and the fluoroquinolone group of antibiotics appear to be active against Cp; macrolides are usually used for Cp infections.9,15,16 There is no defined period for antibiotic therapy but a few suggestions have been proposed by the infectious disease departments of different institutions.15,17 Antibiotic therapy may be stopped when the Cp IgG level is under 1/32 titer.8,15,17 Some have suggested that antibiotics should be used for 6 or 12 months because Cp infection is an intracellular infection and a chronic disease.9,16 Our patients used macrolide antibiotics for 12 months on the recommendation of our infectious disease department.
It was recorded in this study that after one year, the average ABI of group A was a little higher than that of group B. After 2 years, there were no graft occlusions in group A, but there were 3 graft occlusions in group B. This result is not meaningful statistically, and it needs to be investigated for a longer period. Macrolide antibiotic therapy also decreased the frequency of angina pectoris and risk of myocardial infarction in patients with coronary disease.8 Vascular surgeons should keep in mind the possibility that Cp may be a risk factor for peripheral atherosclerosis in addition to smoking, diabetes, and hypertension. In the future, patients with peripheral atherosclerosis may be treated with both antibiotic and antiplatelet therapy, according to the Cp IgG or IgA levels in their serum.
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REFERENCES
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- Fuster V, Badimon L, Badimon JJ, Chesebro JH. The pathogenesis of coronary artery disease and the acute coronary syndromes (1). New Engl J Med 1992;326:242–50.[Medline]
- Altemose GT, Wiener DH. Control of risk factors in peripheral vascular disease. Surg Clin North Am. 1998;78(3):36–84.
- 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. JAMA 1992;268:68–72.[Abstract/Free Full Text]
- Kuo CC, Shor A, Campbell LA, Fukushi H, Patton DL, Grayston JT. Demonstration of Chlamydia pneumoniae in atherosclerotic lesions of coronary arteries. J Infect Dis 1993;167:841–9.[Medline]
- Sirmatel F, Gencay M. Prevalence of Chlamydia pneumoniae specific antibody immunoglobulin G in blood donors. Proceedings of the 6th scientific meeting of the European Society of Chemotherapy, Istanbul, May 20–22, 1999.
- Cristhopher KZ, Seymour G. Artery wall pathology in atherosclerosis. In: Rutherford RB, editor. Vascular surgery. 4th ed. Philadelphia, London, Toronto: WB Saunders, 1995:204–22.
- Tan P, Luscinskas FW, Homer-Vanniasinkam S. Cellular and molecular mechanisms of inflammation and thrombosis. Eur J Vasc Endovasc Surg 1999;17:373–89.[Medline]
- Lindholt JS, Fasting H, Henneberg EW, Ostergaard L. A review of Chlamydia pneumoniae and atherosclerosis. Eur J Vasc Endovasc Surg 1999;17:283–9.[Medline]
- Saikku P, Leinonen M, Mattila K, Ekman MR, Nieminen MS, Makela PH, et al. Serological evidence of an association of a novel Chlamydia, TWAR, with chronic coronary heart disease and acute myocardial infarction. Lancet 1988;2:983–6.[Medline]
- Stille W, Dittmann R. Arteriosclerosis as a sequela of chronic Chlamydia pneumoniae infection. Herz 1998;23:185–92.[Medline]
- Saikku P, Leinonen M, Tenkanen L, Linnanmaki E, Ekman MR, Manninen V, et al. Chronic Chlamydia pneumoniae infection as a risk factor for coronary heart disease in the Helsinki Heart Study. Ann Intern Med 1992;116:273–8.[Abstract/Free Full Text]
- Yamashita K, Ouchi K, Shirai M, Gondo T, Nakazawa T, Ito H. Distribution of Chlamydia pneumoniae infection in the atherosclerotic carotid artery. Stroke 1998;29:773–8.[Abstract/Free Full Text]
- Shor A, Kuo CC, Patton DL. Detection of Chlamydia pneumoniae in coronary arterial fatty streaks and atheromatous plaques. S Afr Med J 1992;82:158–61.[Medline]
- Sirmatel F, Ustunsoy H, Sirmatel O, Akdemir I, Dikensoy O. The relationship between Chlamydia pneumoniae seropositivity and peripheral vascular diseases, acute myocardial infarction and late onset asthma. Infection 2003;31:367–8.[Medline]
- Orfila J. Antibiotic susceptibility of Chlamydia pneumoniae. J Infect Dis 2000;181 Suppl 3:S455.[Medline]
- Stamm WE. Potential for antimicrobial resistance in Chlamydia pneumoniae. J Infect Dis 2000;181 Suppl 3:S456–9.[Medline]
- Kutlin A, Roblin PM, Hammerschlag MR. In vitro activities of azithromycin and ofloxacin against Chlamydia pneumoniae in a continuous-infection model. Antimicrob Agents Chemother 1999;43:2268–72.[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
