Detection of Chlamydia pneumoniae antigenin PBMNCs of healthy blood donors

Comparison of Five PCR Assays for DetectingChlamydophila pneumoniaeDNA

We compared five different polymerase chain reaction (PCR) assays for the detection of Chlamydophila pneumoniae DNA using highly purified elementary bodies (EBs) and peripheral blood mononuclear cells (PBMCs) from healthy blood donors. The primers were as follows; two targeting the 16S rRNA gene, one targeting the ompA gene, one targeting the Pst-I gene, and one targeting the 53 kDa outer membrane protein gene. The 16S rRNA touchdown enzyme time release (TETR) PCR, the ompA nested PCR and the 53 kDa nested PCR were the most sensitive assays and could detect one or more EB per assay. These three PCRs also had the same reproducibility, but the minimal amount of C. pneumoniae that could be reproducibly detected (10 of 10 testing positive) was 20 EBs. In a sample of specimens from healthy blood donors, we found 5 of 77 (6.5%) PBMCs specimens to have C. pneumoniae DNA according to the nested ompA PCR. Specimens with the 16S rRNA TETR and 53 kDa nested assays were found to have C. pneumoniae DNA 7 of 77 (9.1%) and 18 of 77 (23.4%) specimens, respectively. The other two assays failed to detect even a single positive. However, the detection rate decreased with repeated testing of the same samples. Our newly designed 53 kDa nested PCR may be as useful as the other four recommended PCR assays and may be a more useful assay for the detection of C. pneumoniae DNA from PBMCs.

Chlamydophila pneumoniae in human immortal Jurkat cells and primary lymphocytes uncontrolled by interferon-γ

Lymphocytes are a potential host cell for Chlamydophila pneumoniae, although why the bacteria must hide in lymphocytes remains unknown. Meanwhile, interferon (IFN)-γ is a crucial factor for eliminating chlamydiae from infected cells through indoleamine 2,3-dioxygenase (IDO) expression, resulting in depletion of tryptophan. We therefore assessed if lymphocytes could work as a shelter for the bacteria to escape IFN-γ. C. pneumoniae grew normally in human lymphoid Jurkat cells, even in the presence of IFN-γ or under stimulation with phorbol myristate acetate plus ionomycin. Although Jurkat cells expressed IFN-γ receptor CD119, their lack of IDO expression was confirmed by RT-PCR and western blotting. Also, C. pneumoniae survived in enriched human peripheral blood lymphocytes, even in the presence of IFN-γ. Furthermore, C. pneumoniae in spleen cells obtained from IFN-γ knockout mice with C57BL/6 background was maintained in a similar way to wild-type mice, supporting a minimal role of IFN-γ-related response for eliminating C. pneumoniae from lymphocytes. Thus, we concluded that IFN-γ did not remove C. pneumoniae from lymphocytes, possibly providing a shelter for C. pneumoniae to escape from the innate immune response, which has direct clinical significance.

Jurkat cell proliferation is suppressed by Chlamydia (Chlamydophila) pneumoniae infection accompanied with attenuation of phosphorylation at Thr389 of host cellular p70S6K

Chlamydia (Chlamydophila) pneumoniae infects T lymphocytes and multiplies within them. Our previous studies have indicated that C. pneumoniae infection suppresses proliferation of peripheral blood mononuclear cells stimulated with Staphylococcus-enterotoxin B; however, the mechanism of suppression was unclear. In this study, we explored the molecular mechanism involved in C. pneumoniae infection by using human acute T cell leukemia cell line, Jurkat E6-1. Proliferation of Jurkat cells was suppressed in an m.o.i.-dependent manner by C. pneumoniae infection. The suppression by the infection was particularly evident during the initial 24h of the infection, and down modulation of cyclin D3 protein levels were observed at the same time period by immunoblot analysis. The suppression of the Jurkat cell proliferation and the down modulation of cyclin D3 protein level were only induced by viable C. pneumoniae infection, not by exposure to UV-killed or heat-killed C. pneumoniae. Phosphorylations at Thr308 and Ser473 of AKT were induced by C. pneumoniae infection; however, phosphorylation at Thr389 of the downstream kinase, p70S6K was inhibited by unidentified mechanism associated with C. pneumoniae infection. Taking into account that G1 arrest of the C. pneumoniae infected Jurkat cells were not observed and that p70S6K is one of the most important regulators of protein synthesis, it was suggested that the suppression of Jurkat cell proliferation by C. pneumoniae was at least in part mediated by down modulation of protein synthesis through attenuation of Thr389 phosphorylation of p70S6K.

Diverse bacteria promote macrophage foam cell formation via Toll-like receptor-dependent lipid body biosynthesis

AIM

Atherosclerotic lesions contain DNA signatures from a wide variety of bacteria, although little is known of how exposure to these organisms may modulate the accumulation of lipids in macrophages.

METHODS

To address this, a panel of nine bacteria representing those most frequently reported to be present in human atheroma were examined for their potential to promote lipid accumulation in human primary monocytes and murine J774 macrophages.

RESULTS

All bacteria examined, and defined stimulants of Toll-like receptors (TLRs) 2, 3, 4, 5 and 9, induced lipid body formation and cholesterol ester accumulation in a dose-dependent manner. The mechanisms of bacteria-mediated foam cell formation were found to be dependent on TLR2 and/or TLR4 signalling, but independent of lipoprotein oxidation pathways, since lipid accumulation was significantly inhibited by the TLR4 inhibitors polymyxin-B and TAK-242, or the TLR2 and TLR4 inhibitor oxidised palmitoyl-arachidonyl-phosphatidyl-choline, but not by the scavenger receptor blocker polyinosinic acid or the antioxidant butylated hydroxytoluene. A number of genes involved in lipid body biosynthesis, including perilipin-A, stearoyl-coenzyme-A desaturase 1, fatty acid synthase and HMG-CoA reductase were upregulated in response to TLR4 stimulation.

CONCLUSIONS

The bacterial debris observed in human atheroma, which is currently considered to be harmless, may have potential to contribute to disease progression via TLR-dependent lipid body formation in macrophages.

Stability of Chlamydophila pneumoniae in a harsh environment without a requirement for acanthamoebae

The effect of actual interactions between Chlamydophila pneumoniae and amoebae (Acanthamoeba) on the survival of C. pneumoniae was investigated. C. pneumoniae and amoebae were detected in 75 soil samples by IFU assay and PCR. Although C. pneumoniae could not be cultured, the DNA prevalence of C. pneumoniae and amoebae in natural soil was 20% and 92% (no correlation between the prevalence of DNA was observed). The viability of C. pneumoniae spiked in autoclaved soil was assessed by IFU assay and RT-PCR. Although the number of infective progeny decreased for three days, transcripts of C. pneumoniae were detected for up to 98 days independently of amoebae. The stability of C. pneumoniae in liquid medium was also assessed by IFU assay and transmission electron microscopy. The bacteria could survive at 15 degrees C for 14 days independently of amoebae. Bacteria cultured without amoebae were confirmed to have normal structures. Thus, the presence of amoebae has no effect on C. pneumoniae survival, and the bacteria can survive in the absence of host cells for an extended period of time.

Successful removal of Chlamydia pneumoniae from plateletpheresis products collected using automated leukoreduction hemapheresis techniques

Chlamydia pneumoniae (Cp) is an obligate intracellular pathogen associated with a variety of maladies. Best known for its involvement in community-acquired pneumonia outbreaks; the potential role of Cp in diverse illnesses is a topic of increasing interest and investigation. Previous studies suggested that white blood cells from normal blood donors harboring this agent may be eliminated through leukoreduction by filtration. Here we examine the ability and efficacy of apheresis-related leukoreduction for its effect on the carriage and potential infectivity of these organisms in the preparation of platelet products. Matched pre-apheresis peripheral blood (PB) samples and product samples obtained from healthy plateletpheresis donors were analyzed for the presence and potential infectivity of Cp organisms by direct smear inspection and tissue culture techniques. Antibody seroreactivity directed towards the organism was assessed using a solid phase immunoassay. Forty-eight percent of the donor blood samples exhibited elevated anti-Cp antibody titers (> or =200). Specimens from 31 (27%) and 34 (30%) of 115 plateletpheresis donors were positive for the presence of Cp organisms in their pre-apheresis PB samples when analyzed by direct smear examination and culture, respectively. Examination of the 115 post-leukodepleted plateletpheresis product samples revealed only two (1.7%) and one (0.009%) product(s) to be smear-positive and culture-positive, respectively. Certain plateletpheresis donors may harbor infectious Cp organisms in circulating WBC. Collections from such donors of apheresis platelet products using standard apheresis leukoreduction strategies appear successful in markedly decreasing or eliminating the organisms found in the final products.

Development of diabetes in non-obese diabetic mice promotes Chlamydia pneumoniae dissemination from lung to peripheral blood

We examined a possible association between development of diabetes in non-obese diabetic (NOD) mice and dissemination of Chlamydia (Chlamydophila) pneumoniae from lung to peripheral blood. By real-time reverse transcription-polymerase chain reaction (RT-PCR) with primers for C. pneumoniae 16S rRNA, following multiple intranasal inoculations, we detected bacteria in lung in NOD mice with diabetes (38.5%) as well as Institute of Cancer Research, USA (ICR) mice (40%), but prevalence of bacteria in NOD mice without diabetes (pre-diabetic NOD mice and non-diabetic retired NOD mice) was very low (4.8%). The bacteria were only detected in peripheral blood mononuclear cells (PBMCs) cultured with hydrocortisone of the NOD mice with diabetes (53.8%). Results of immunostaining with fluorescein isothiocyanate-conjugated antichlamydia monoclonal antibody also showed the presence of bacterial antigens in the lungs and the PBMCs judged as positive by the RT-PCR. However, C. pneumoniae from cultured PBMCs of all NOD mice was undetected by cultivation method with inclusion-forming units assay. In addition, no influence of C. pneumoniae intranasal inoculation on development of diabetes in NOD mice was confirmed. Thus, the development of diabetes in NOD mouse appears to be one of critical factors for promoting the dissemination of C. pneumoniae from lung to peripheral blood.

Detection of Chlamydia in the peripheral blood cells of normal donors using in vitro culture, immunofluorescence microscopy and flow cytometry techniques

BACKGROUND

Chlamydia trachomatis (Ct) and Chlamydia pneumoniae (Cp) are medically significant infectious agents associated with various chronic human pathologies. Nevertheless, specific roles in disease progression or initiation are incompletely defined. Both pathogens infect established cell lines in vitro and polymerase chain reaction (PCR) has detected Chlamydia DNA in various clinical specimens as well as in normal donor peripheral blood monocytes (PBMC). However, Chlamydia infection of other blood cell types, quantification of Chlamydia infected cells in peripheral blood and transmission of this infection in vitro have not been examined.

METHODS

Cp specific titers were assessed for sera from 459 normal human donor blood (NBD) samples. Isolated white blood cells (WBC) were assayed by in vitro culture to evaluate infection transmission of blood cell borne chlamydiae. Smears of fresh blood samples (FB) were dual immunostained for microscopic identification of Chlamydia-infected cell types and aliquots also assessed using Flow Cytometry (FC).

RESULTS

ELISA demonstrated that 219 (47.7%) of the NBD samples exhibit elevated anti-Cp antibody titers. Imunofluorescence microscopy of smears demonstrated 113 (24.6%) of samples contained intracellular Chlamydia and monoclonals to specific CD markers showed that in vivo infection of neutrophil and eosinophil/basophil cells as well as monocytes occurs. In vitro culture established WBCs of 114 (24.8%) of the NBD samples harbored infectious chlamydiae, clinically a potentially source of transmission, FC demonstrated both Chlamydia infected and uninfected cells can be readily identified and quantified.

CONCLUSION

NBD can harbor infected neutrophils, eosinophil/basophils and monocytes. The chlamydiae are infectious in vitro, and both total, and cell type specific Chlamydia carriage is quantifiable by FC.

Degradation of Chlamydia pneumoniae by peripheral blood monocytic cells

Chlamydia pneumoniae is a common human respiratory pathogen that has been associated with a variety of chronic diseases, including atherosclerosis. The role of this organism in the pathogenesis of atherosclerosis remains unknown. A key question is how C. pneumoniae is transferred from the site of primary infection to a developing atherosclerotic plaque. It has been suggested that circulating monocytes could be vehicles for dissemination of C. pneumoniae since the organism has been detected in peripheral blood monocytic cells (PBMCs). In this study we focused on survival of C. pneumoniae within PBMCs isolated from the blood of healthy human donors. We found that C. pneumoniae does not grow and multiply in cultured primary monocytes. In C. pneumoniae-infected monocyte-derived macrophages, growth of the organism was very limited, and the majority of the bacteria were eradicated. We also found that the destruction of C. pneumoniae within infected macrophages resulted in a gradual diminution of chlamydial antigens, although some of these antigens could be detected for days after the initial infection. The detected antigens present in infected monocytes and monocyte-derived macrophages represented neither chlamydial inclusions nor intact organisms. The use of {N-[7-(4-nitrobenzo-2-oxa-1,3-diazole)]}-6-aminocaproyl-d-erythro-sphingosine as a vital stain for chlamydiae proved to be a sensitive method for identifying rare C. pneumoniae inclusions and was useful in the detection of even aberrant developmental forms.

Asymptomatic carotid atherosclerosis is associated with circulating chlamydia pneumoniae DNA in younger normotensive subjects in a general population survey

OBJECTIVE

Chlamydia pneumoniae infection has been associated with atherosclerosis, but serodiagnosis is unreliable in predicting vascular infection. Direct detection of circulating chlamydial DNA in peripheral blood mononuclear cells (PBMCs) was thus evaluated as a marker for cardiovascular risk in a general population survey using the common carotid intima-media thickness (IMT) as surrogate marker of asymptomatic atherosclerosis.

METHODS AND RESULTS

C pneumoniae DNA in PBMCs was determined by nested polymerase chain reaction and associated with IMT for 1032 healthy participants of a general population survey who were within the highest or lowest IMT distribution quartile. C pneumoniae DNA was more prevalent in those with increased IMT (13.4% versus 10.7%), but this was not significant in univariate and of borderline significance in multivariate analysis. Testing for potential effect modifications by known strong determinants of an increased IMT in group interaction analysis revealed an independent association between C pneumoniae DNA and IMT in normotensive subjects (odds ratio [OR], 2.06; 95% CI, 1.05 to 4.03; P=0.04) and in those <70 years old (OR, 1.84; 95% CI, 1.06 to 3.19; P=0.03).

CONCLUSIONS

Asymptomatic atherosclerosis is associated with circulating C pneumoniae DNA independently of classical cardiovascular risk factors in normotensive subjects and those <70 years old. C pneumoniae has been implicated in atherogenesis. We determined the association of chlamydial DNA in peripheral blood mononuclear cells with the carotid intima-media thickness from 1032 healthy subjects from a general population survey. A stratified group interaction analysis revealed an independent association in normotensive subjects and those <70 years old.

Production of prostaglandin E2 in monocytes stimulated in vitro by Chlamydia trachomatis, Chlamydophila pneumoniae, and Mycoplasma fermentans

Chlamydia trachomatis (CT) as well as Chlamydophila pneumoniae (CP) cause chronic inflammatory diseases in humans. Persistently infected monocytes are involved in the pathogenesis by inducing mediators of inflammation. An in vitro system of chlamydial persistence in human peripheral blood monocytes (HPBM) was used to investigate prostaglandin E(2) (PGE(2)) production and the expression of the key enzyme for prostaglandin production, cyclooxygenase-2 (COX-2). PGE(2) production was determined by PGE(2)-ELISA of HPBM-culture supernatants. Cox-2 mRNA expression was measured by real-time RT-PCR of total RNA isolated from HPBM. Both, CT and CP, stimulated PGE(2) production of HPBM in vitro. Equivalent numbers of CT per host cell induced a higher PGE(2)-response compared to CP. The amount of synthesized PGE(2) depended on the chlamydial multiplicity of infection (MOI). Even at an MOI of 10 the amount of CT- and CP-induced prostaglandin, respectively, was lower than the amount of prostaglandin induced by E. coli lipopolysaccharide (LPS) at a concentration of 10microg/ml. In contrast to stimulation with LPS, Chlamydia-induced PGE(2) production as well as cox-2 mRNA decreased after day 1 post infection (p.i.). These data indicate that Chlamydia stimulate PGE(2) production in human monocytes. Since Chlamydia are often contaminated by mycoplasma, the influence of mycoplasma on the prostaglandin production was investigated additionally. Mycoplasma fermentans (MF) also stimulated PGE(2) production. The co-infection of mycoplasma and Chlamydia resulted in an additive effect in the production of PGE(2). Thus it is important to use host cells and Chlamydia free of mycoplasma contamination for the analysis of Chlamydia-induced prostaglandin production.

Detection of Chlamydophila pneumoniae in dendritic cells in atherosclerotic lesions

Dendritic cells (DCs) populate atherosclerotic lesions and might be involved in the regulation of immune reactions in atherosclerosis. The present work was undertaken to examine a possible association of DCs with Chlamydophila pneumoniae in human atherosclerotic plaques obtained by endarterectomy. C. pneumoniae was identified in 17 of 60 (28%) atherosclerotic plaques by a combination of immunohistochemistry and polymerase chain reaction (PCR). Double immunohistochemistry identified the presence of C. pneumoniae within S100(+) DCs that were localised predominantly in the deep layer of the intima under the necrotic core. Quantitative analysis showed that there were no differences in the numbers of DCs between C. pneumoniae(+) and C. pneumoniae(-) groups of atherosclerotic specimens. There were also no differences in the expression of Lag-antigen and HLA-DR by DCs between the groups of specimens. Markers of DC activation CD80 and CD86 were absent from both groups of specimens. Flow cytometry analysis of the effects of C. pneumoniae infection on immature monocyte-derived DCs in vitro showed no changes in the expression of CD1a, MHC class II, CD80 and CD86. The results of this study demonstrate that C. pneumoniae might infect DCs within the atherosclerotic intima but whether the presence of C. pneumoniae in DCs affects the intensity of immune reactions in atherosclerosis needs further clarification.

Association of Peripheral Mononuclear Cells Containing Chlamydia Pneumoniae DNA with Acute Coronary Syndrome and Stable Coronary Artery Disease in Japanese Subjects

To clarify the association of Chlamydia pneumoniae DNA in peripheral blood mononuclear cells (PBMCs) with acute coronary syndrome (ACS) and stable coronary artery disease (CAD) in Japanese adults, touchdown-nested polymerase chain reaction was used to detect the presence of C. pneumoniae DNA. The prevalence of C. pneumoniae DNA in PBMCs was similar in a comparison of 88 patients (52.3%) with ACS, 164 patients (50.0%) with stable CAD, and 88 control subjects (50.0%). Temporal changes in the prevalence of C. pneumoniae DNA in PBMCs were also assessed every 3 months during a 1-year period (n=59). The prevalence was significantly higher in the first 3-month period (January through March) than in any of the other 3-month periods. In conclusion, the prevalence of C. pneumoniae DNA in PBMCs in patients with ACS or stable CAD was comparable to that in control populations. Furthermore, the presence of circulating C. pneumoniae was strongly associated with seasonal variability.

Risks of transfusion-transmitted infections: 2003

PURPOSE OF REVIEW

While the risks of transfusion-transmitted human immunodeficiency virus, hepatitis C virus, and human T-cell leukemia virus I/II continue to decrease, additional threats to transfusion safety are posed by emerging "new" infectious diseases.

RECENT FINDINGS

Following the introduction of nucleic acid testing for human immunodeficiency virus and hepatitis C virus, the American Red Cross estimates the risk of transfusion-transmitted human immunodeficiency virus to be 1:1,215,000 (per unit transfused) and 1:1,935,000 for transfusion-transmitted hepatitis C virus. Hepatitis B virus nucleic acid testing has not been implemented, and the risk of transfusion-transmitted hepatitis B virus in the United States remains relatively high at an estimated 1:205,000. The risk of transfusion-transmitted human T-cell leukemia virus I/II is 1:2,993,000, based on Red Cross estimates. Nucleic acid testing for West Nile virus began in the United States in 2003 under an investigational new drug program. No approved laboratory tests are available to screen the blood for Chagas disease, malaria, severe acute respiratory syndrome, or variant Creutzfeldt-Jakob disease.

SUMMARY

Prevention of these potential transfusion-transmitted infections is addressed by deferring potential donors whose personal behaviors or travel histories place them at risk.

Prevalence of viable Chlamydia pneumoniae in peripheral blood mononuclear cells of healthy blood donors

BACKGROUND

Demonstration of viable Chlamydia (Chlamydophila) pneumoniae in peripheral blood mononuclear cells (PBMNCs) is essential to understand the involvement of C. pneumoniae in atherosclerosis. Nevertheless, the prevalence of viable C. pneumoniae in the blood of healthy donors has not yet been studied.

STUDY DESIGN AND METHODS

The presence of C. pneumoniae transcript in PBMNCs from blood of healthy human donors was assessed by real-time reverse transcription-polymerase chain reaction (RT-PCR) with primers for C. pneumoniae 16S rRNA, which is more sensitive than genomic-DNA-based analysis, and by the use of staining with fluorescein isothiocyanate-conjugated chlamydia monoclonal antibody (MoAb).

RESULTS

Thirteen of 70 donors (18.5%) showed the presence of bacterial transcript in cultured PBMNCs. The prevalence of bacterial detection and bacterial numbers was significantly increased in PBMNC cultures incubated with cycloheximide. Immunostaining of PBMNCs with antichlamydial MoAb also revealed the presence of bacterial antigen in the PBMNCs judged as positive. Nevertheless, cultivation of C. pneumoniae from all PCR-positive donors was unsuccessful. There was no significant correlation between the presence of chlamydia and either sex or current smoking habits. A possible age variation, however, in the presence of chlamydia in blood of healthy donors was suggested by the results obtained.

CONCLUSION

The bacterial transcripts in PBMNCs obtained from healthy donors were detected by the RT-PCR method. Viable C. pneumoniae may be present in healthy human PBMNCs.

Chlamydia pneumoniae resists antibiotics in lymphocytes

Chlamydia pneumoniae infection of lymphocytes in blood has been well documented, and it is apparent that control of this pathogen in these cells may be critical in the development of chronic inflammatory diseases associated with infection by this bacterium. The activity of antibiotics against C. pneumoniae in lymphocytes was assessed in this study by utilizing an in vitro infection model with lymphoid cells. The results obtained indicated that although all of the antibiotics tested showed remarkable activity against bacterial growth in epithelial cells, C. pneumoniae in lymphocytes was less susceptible to antibiotics than was bacterial growth in epithelial cells, which are widely used for the evaluation of anti-C. pneumoniae antibiotics.

A lack of serologic evidence of transmission of Chlamydia pneumoniae by transfusion of buffy coat-depleted RBCs

BACKGROUND

Recent studies have shown that a high percentage of blood donors harbor Chlamydia pneumoniae DNA and antigens within their PBMNCs. The aim of the present study was to investigate whether recipients of RBC transfusions who were seronegative for C. pneumoniae before transfusion showed any evidence of seroconversion after transfusion.

STUDY DESIGN AND METHODS

Patients who were possible recipients of RBC transfusion and negative in a screen test for IgG antibodies against C. pneumoniae at the time of blood group determination were candidates to be included in the study. The patients were contacted 3.0 to 3.5 months after the blood group determination, and those who accepted to participate agreed that another venous blood sample could be taken.

RESULTS

Among the patients who participated, 53 had become recipients of RBC transfusion (transfused group), and 51 later did not receive any RBC transfusion (control group). No significant change was found in IgG titer against C. pneumoniae between the first and the second sample from the same patient, in either the transfused group or the control group.

CONCLUSION

In our study, which was limited to 53 seronegative recipients of RBC units from seropositive donors, we found no serologic evidence that C. pneumoniae could be transmitted by RBC transfusion.

Association of circulating Chlamydia pneumoniae DNA with cardiovascular disease: a systematic review

BACKGROUND

Chlamydia pneumoniae antigens, nucleic acids, or intact organisms have been detected in human atheroma. However, the presence of antibody does not predict subsequent cardiovascular (CV) events. We performed a systematic review to determine whether the detection of C. pneumoniae DNA in peripheral blood mononuclear cells (PBMC) was associated with CV disease.

METHODS

We sought studies of C. pneumoniae DNA detection in PBMC by polymerase chain reaction (PCR) among patients with CV disease or other clinical conditions. We pooled studies in which CV patients were compared with non-diseased controls. We analyzed differences between studies by meta-regression, to determine which epidemiological and technical characteristics were associated with higher prevalence.

RESULTS

Eighteen relevant studies were identified. In nine CV studies with control subjects, the prevalence of circulating C. pneumoniae DNA was 252 of 1763 (14.3%) CV patients and 74 of 874 (8.5%) controls, for a pooled odds ratio of 2.03 (95% CI: 1.34, 3.08, P < 0.001). Prevalence was not adjusted for CV risk factors. Current smoking status, season, and age were associated with C. pneumoniae DNA detection. High prevalence (>40%) was found in patients with cardiac, vascular, chronic respiratory, or renal disease, and in blood donors. Substantial differences between studies were identified in methods of sampling, extraction, and PCR targets.

CONCLUSIONS

C. pneumoniae DNA detection was associated with CV disease in unadjusted case-control studies. However, adjustment for potentially confounding measures such as smoking or season, and standardization of laboratory methods, are needed to confirm this association.