Chlamydia pneumoniae does not influence atherosclerotic plaque behavior in patients with established carotid artery stenosis

Role of gut microbiota in atherosclerosis

Infections have been linked to the development of cardiovascular disease and atherosclerosis. Findings from the past decade have identified microbial ecosystems residing in different habitats of the human body that contribute to metabolic and cardiovascular-related disorders. In this Review, we describe three pathways by which microbiota might affect atherogenesis. First, local or distant infections might cause a harmful inflammatory response that aggravates plaque development or triggers plaque rupture. Second, metabolism of cholesterol and lipids by gut microbiota can affect the development of atherosclerotic plaques. Third, diet and specific components that are metabolized by gut microbiota can have various effects on atherosclerosis; for example, dietary fibre is beneficial, whereas the bacterial metabolite trimethylamine-N-oxide is considered harmful. Although specific bacterial taxa have been associated with atherosclerosis, which is supported by increasing mechanistic evidence, several questions remain to be answered to understand fully how the microbiota contributes to atherosclerosis and cardiovascular disease. Such knowledge might pave the way for novel diagnostics and therapeutics based on microbiota.

Chlamydia pneumoniae is not detectable in subretinal neovascular membranes in the exudative stage of age-related macular degeneration

PURPOSE

Age-related macular degeneration (AMD) is the most frequent cause of severe visual impairment in western countries, but its aetiology remains unclear. A growing body of evidence suggests that inflammation contributes to the pathogenesis of AMD, similarly to that shown for atherosclerosis. In view of a number of shared risk factors between the two entities and the hypothesized link between Chlamydia pneumoniae infection and atherosclerosis, we investigated whether C. pneumoniae might be involved in exudative AMD.

METHODS

To examine whether C. pneumoniae contributes to the development of subretinal neovascular (SRNV) membranes in AMD, 13 consecutive SRNV membranes surgically excised from patients with exudative AMD were collected and assayed for the presence of C. pneumoniae or other bacterial pathogens by means of polymerase chain reaction (PCR).

RESULTS

The age of patients ranged from 68 to 85 years (median 73.5 years). In all 13 SRNV membranes, no DNA of either C. pneumoniae or other pathogens was found by PCR.

CONCLUSIONS

These findings indicate that C. pneumoniae is not associated with the development of SRNV membranes in exudative AMD.

Discordant detection of Chlamydia pneumoniae in patients with carotid artery disease using polymerase chain reaction, immunofluorescence microscopy and serological methods

AIM

To determine the presence of Chlamydia pneumoniae in carotid plaque and peripheral blood mononuclear cells (PBMCs) using a combination of serology, direct antigen detection by immunofluorescence (IF) microscopy and polymerase chain reaction (PCR), and to compare the results obtained from each assay.

METHODS

A total of 54 atherosclerotic carotid plaques were tested for the presence of Chlamydia by PCR and IF methods. Of these 54 patients with carotid artery disease (CAD), 43 were also tested for the presence of C. pneumoniae DNA in PBMCs and for Chlamydia antibodies using two methods, the Medac Chlamydien rELISA and Focus Chlamydia microimmunofluorescence (MIF) methods.

RESULTS

Eighteen of the 54 (33%) carotid specimens were positive for the presence of C. pneumoniae DNA, whereas only two of 43 (5%) patients had C. pneumoniae DNA present within their PBMC fraction. Chlamydial antibodies were detected by MIF and/or rELISA in 56% (24/43) of the patients tested. None of the 43 patients was C. pneumoniae positive in all of the test specimens (plaque, PBMCs and serum).

CONCLUSIONS

Chlamydia pneumoniae is commonly found in Australian patients with CAD. Serology and PCR-based detection of C. pneumoniae in PBMCs and plaque give highly discordant results.

Demonstration of intracellular microorganisms (Rickettsia spp., Chlamydia pneumoniae, Bartonella spp.) in pathological human aortic valves by PCR

OBJECTIVES

Rickettsiae, which causes vasculitis, has not been linked to atherosclerotic cardiovascular disease in contrast to Chlamydia pneumoniae whose association with coronary artery disease and with sclerotic heart valves in patients undergoing aortic valve replacement is well established, even if causality is yet to unproven. In the search for any of these infectious agents, 84 pathological and 15 normal aortic heart valves of patients undergoing forensic autopsy were analysed by PCR and DNA-sequencing.

METHODS

Two to four pieces of all valves were examined by semi-nested PCR, with primers specific for 16S rDNA, citrate synthase (gltA) and 17 kDa outer membrane protein (OMP) genes.

RESULTS

Genetic material from Rickettsia spp. and C. pneumoniae was found in 17 (20.2%) and 22 (26.2%), respectively, of the 84 pathological aortic valves. In 35 (41.7%) of these 84 valves either C. pneumoniae or Rickettsia spp. were detected by PCR and in six cases (7.1%) these two organisms co-existed. In one case with Lambl's excrescences, previously considered as aseptic, presence of rickettsia-like organisms also was demonstrated by light microscopy, immunohistochemistry and sequencing of the amplified PCR product showing 100% homology with the published sequence for R. helvetica. In three of the 15 control valves, genetic material from only C. pneumoniae was detected compared to Rickettsia spp. that was significantly detected only in the pathological valves (Fisher's Exact test, 1-sided p = 0.046).

CONCLUSIONS

The findings suggest that Rickettsia spp. also have a role in the pathogenesis of aortic valve disease.

Is the perceived association between Chlamydia pneumoniae and vascular diseases biased by methodology?

Inter- and intralaboratory inconsistencies in detection rates of Chlamydia pneumoniae in vascular specimens have been demonstrated. In this study, 66 vascular tissue specimens from 66 patients with vascular disease were tested by three PCR assays: a 16S PCR-based reverse line blot (RLB) assay, a single-step PCR, and a nested PCR. Also, we explored the impacts of different DNA polymerase enzymes on the results based on gel electrophoresis and hybridization. The PCR results by gel electrophoresis in the single-step PCR depended on which DNA polymerase was used. All samples were negative with AmpliTaq Gold DNA polymerase, and 54.5% (36 of 66) were positive with the conventional Taq DNA polymerase. All samples were negative after hybridization with a C. pneumoniae-specific probe. In the nested PCR, all specimens were negative by gel electrophoresis and after hybridization. The RLB assay failed to detect C. pneumoniae in any specimen; however, 20 specimens were Chlamydia sp. positive. The sequence analysis of six of these samples demonstrated Chlamydia-like organisms. RLB detected Chlamydia sp. DNA in water and in the elution buffer after passage of the Qiagen columns (11 of 40). This study identified factors that may influence the detection of C. pneumoniae DNA in vascular tissues and consequently bias the perception of a link between C. pneumoniae and vascular diseases. The following are strongly recommended: to use DNA polymerases that have to be activated, to decontaminate with dUTP-uracil-DNA glycosylase, to hybridize with specific probes, to include sufficient controls, and to use molecular grade water.

Heart disease: the greatest 'risk' factor of them all

By the turn of the last century, flying in the face of over a hundred years of research and clinical observation to the contrary, medicine abandoned the link between infection and atherogenesis; not because it was ever proven wrong, but because it did not fit in with the trends of a medical establishment convinced that chronic disease such as heart disease must be multifactorial, degenerative and non-infectious. Yet it was the very inability of 'established' risk factors such as hypercholesterolemia, hypertension and smoking to completely explain the incidence and trends in cardiovascular disease that resulted in historically repeated calls to search out an infectious cause, a search that began more than a century ago. Today, half of US heart attack victims have acceptable cholesterol levels and 25% or more have none of the "risk factors" associated with heart disease, including smoking, high blood pressure or obesity, most of which are not inconsistent with being caused by infection. Even the case of the traditionalist's latest 2003 JAMA assault to 'debunk' what they call the "50% risk factor myth" falls woefully short under scrutiny. In one group 30% died of heart disease with a cholesterol of at least 240 mg/dl, a condition which also existed in 21% who did not die during the same period. And the overlap was obvious throughout the so-called risk categories. Under such scrutiny, lead author Greenland conceded that if obesity, inactivity and elevated cholesteriol in the elderly are included, just about everyone has a risk factor and he likened the dilemma of people who do or do not wind up with heart disease akin to the susceptibility of people who are exposed to tuberculosis but do not get the disease. In Infections and Atherosclerosis: New Clues from an old Hypothesis? Nieto stressed the need to extend the possible role of infectious agents beyond the three infections which have in recent years been the focus of research: Cytomegalovirus (CMV) Chlamydia pneumoniae and Helicobactor pylori. Mycobacterial disease shares interesting connections to heart disease. Not only is tuberculosis the only microorganism to depend on cholesterol for its pathogenesis but CDC maps for cardiovascular disease bear a striking similarity to those of State and regional TB case rates. Ellis, Hektoen, Osler, McCallum, Swartz, Livingston and Alexander-Jackson all saw clinical and laboratory evidence of a causative relationship between the mycobacteria and heart disease. And Xu showed that proteins of mycobacterial origin actually led to experimental atherosclerosis in laboratory animals Furthermore present day markers suggested as indicators for heart disease susceptibility such as C-Reactive Protein (CRP), interleukin-6 and homocysteine are all similarly elevated in tuberculosis. It therefore behooves us to explore the link between heart disease and typical and atypical tuberculosis.

Chlamydia pneumoniae and atherosclerosis following carotid endarterectomy

BACKGROUND

Seroepidemiological studies have shown an association between raised antibody titres against Chlamydia pneumoniae, and carotid atherosclerosis or stroke. However, direct evidence for a causal link between arterial infection with C. pneumoniae and carotid disease remains weak. We hypothesized that long-term follow-up of patients with pathologically-proven arterial C. pneumoniae infection might provide further insight into the role of C. pneumoniae in carotid atherosclerosis.

METHODS

We followed a cohort of 70 carotid endarterectomy patients for ipsilateral restenosis, contralateral progression, and all-cause mortality (four year median follow-up period). All patients had presence or absence of C. pneumoniae in their carotid plaques documented by immunohistochemistry after endarterectomy. A survival function was generated and the log-rank test was used to assess the difference in survival between subjects with and without documented chlamydial infection in their plaque.

RESULTS

Baseline demographic and cardiovascular risk factors were similar between the two groups, and survival analysis demonstrated no difference (p>0.05) in all-cause mortality, or all-cause mortality combined with restenosis and progression.

CONCLUSIONS

Our data finds no causal role for C. pneumoniae in restenosis or progression of carotid disease or mortality in this patient population with advanced carotid atherosclerosis.

Failure to detect Chlamydia pneumoniae DNA in cerebral aneurysmal sac tissue with two different polymerase chain reaction methods

OBJECTIVE

Chlamydia pneumoniae (C pneumoniae) is a common cause of a usually mild, community acquired pneumonia. This organism, however, can spread from the respiratory tract into other parts of the body and has been detected in up to 70% of atheromatous lesions in blood vessels. Although the exact mechanism of the C Pneumoniae contribution to the pathogenesis of atherosclerosis remains unknown, prophylactic antibiotic trials are planned for people at high risk for coronary disease.

METHOD

In this study the authors aimed to investigate C pneumoniae DNA content in the cerebral aneurysmal sac tissue with the aid of polymerase chain reaction (PCR) method. C pneumoniae DNA was searched in 15 surgically clipped and removed aneurysmal sac tissue and in two tumour (an ependymoma of the fourth ventricle and a craniofaringoma) samples by touchdown enzyme time release PCR (TETR PCR) targeting 16S rRNA gene and by nested PCR targeting ompA gene.

RESULTS

Both PCR methods were sensitive to detect in C pneumoniae 4x10(-2) genomes. C pneumoniae DNA was not detected in any of the 17 sample tissues of these patients.

CONCLUSION

The contribution of C pneumoniae in the development of intracranial aneurysms cannot be excluded despite the results of this study. Further studies on the possible role of C pneumoniae or any other micro-organisms in the pathogenesis of aneurysms should be performed.

Chlamydia pneumoniae DNA in patients with symptomatic carotid atherosclerotic disease

OBJECTIVE

We evaluated the correlation between the presence of Chlamydia pneumoniae in atherosclerotic carotid plaques, lymph nodes, and peripheral blood mononuclear cells (PBMCs), and symptomatic carotid atherosclerotic disease.

METHODS

Fifty-one consecutive patients undergoing carotid endarterectomy were enrolled; 18 of the 51 patients had symptomatic disease, whereas 33 had asymptomatic disease. Detection of C pneumoniae DNA in atherosclerotic carotid plaques, lymph nodes, and PBMCs was performed with polymerase chain reaction (PCR). C pneumoniae antibodies were measured with a microimmunofluorescence test.

RESULTS

C pneumoniae DNA in atherosclerotic carotid plaques was detected in 44.4% of patients with symptomatic disease and in 30.3% of those with asymptomatic disease (P =.48). C pneumoniae DNA in lymph nodes was detected in 33.3% of patients with symptomatic disease and 18.2% of those with asymptomatic disease (P =.19). Prevalence of C pneumoniae DNA in PBMCs was significantly higher in patients with symptomatic disease (72.2%) compared with those with asymptomatic disease (30.3%) (P =.01). Serologic results support the association between C pneumoniae DNA in PBMCs and symptomatic carotid atherosclerotic disease, because seropositivity for anti-chlamydial immunoglobulin (Ig) A antibodies was significantly higher in PCR-positive PBMCs in patients with symptomatic disease compared with patients with asymptomatic disease (P =.02).

CONCLUSIONS

Detection of C pneumoniae in PBMCs shows that C pneumoniae may be associated with symptomatic carotid atherosclerotic disease. Although we believe there is need for standardization of PCR methods and for assessing sensitivity, specificity, and predictive values of the tests, we suggest that presence of C pneumoniae DNA in PBMCs is a valid surrogate marker of risk for endovascular chlamydial infection. Only long-term cohort studies and interventional trials will clarify the etiopathogenic role of C pneumoniae.

Role of Chlamydia pneumoniae-infected macrophages in atherosclerosis developments of the carotid artery

Chlamydia pneumoniae (C. pneumoniae) infection has been recently accepted as an important cause of atherosclerosis. However, the precise mechanisms remain unclear. The present study was aimed to clarify the distribution link among C. pneumoniae, chlamydial HSP 60, and activated macrophages. Atheromatous carotid plaques were obtained from 40 consecutive carotid endarterectomies (CEA). The specimens were prepared for HE and elastica-van Gieson staining. Parallel sections were stained immunocytochemically with monoclonal antibodies for a C. pneumoniae-specific antigen, chlamydial HSP 60, activated macrophages, and smooth muscle cells. Immunoreactivity for the C. pneumoniae-specific antigen was observed within the endothelial cells, activated macrophages, and smooth muscle cells in 36 of 40 specimens (90%). Chlamydial HSP 60 was found in all specimens positive for the C. pneumoniae-specific antigen, and mainly co-localized with the C. pneumoniae-specific antigen within the activated macrophages. The present results suggest that C. pneumoniae is a key microbial organ that causes atheroma developments in the carotid artery. Chlamydia pneumoniae-infected macrophages may come into the arterial intima and mediate inflammatory and autoimmune processes through the production of chlamydial HSP 60, leading to atherosclerosis.

Limited association of Chlamydia pneumoniae detection with coronary atherosclerosis

The association of Chlamydia pneumoniae (C. pneumoniae) detection with atherosclerosis has been controversial because of recent conflicting results. In order to assess how and to what extent C. pneumoniae detection contributes to atherosclerosis, the association between immunohistochemical detection of C. pneumoniae antigen, intimal lesions, and the intimal thickening ratio was examined in 1674 left anterior descending coronary arterial segments from 100 autopsied Japanese patients being free from coronary heart disease. These specimens contained full spectrum of atherosclerotic lesions as defined by the American Heart Association classification. The intimal thickening ratio increased in C. pneumoniae-positive sections comparing to that in C. pneumoniae-negative sections only in the group with normal intima and diffuse intimal thickening, but there was no such association in the other advanced intimal lesion groups. Furthermore, in 50 C. pneumoniae-positive cases out of 100 investigated, the frequency and extent of immunoreactivity did not associate with progression of intimal lesions or the intimal thickening ratio, and the mean score of C. pneumoniae detection did not correlate with the mean intimal thickening ratio in individual cases. These results suggest only a limited association between C. pneumoniae detection and coronary atherosclerosis development and that C. pneumoniae does not influence promotion of atherosclerotic lesions. The role of C. pneumoniae on atherogenesis may be limited only at the beginning stage of atherosclerosis development.

Inflammation and infection in clinical stroke

Stroke has enormous clinical, social, and economic implications, and demands a significant effort from both basic and clinical science in the search for successful therapies. Atherosclerosis, the pathologic process underlying most coronary artery disease and the majority of ischemic stroke in humans, is an inflammatory process. Complex interactions occur between the classic risk factors for atherosclerosis and its clinical consequences. These interactions appear to involve inflammatory mechanisms both in the periphery and in the CNS. Central nervous system inflammation is important in the pathophysiologic processes occurring after the onset of cerebral ischemia in ischemic stroke, subarachnoid hemorrhage, and head injury. In addition, inflammation in the CNS or in the periphery may be a risk factor for the initial development of cerebral ischemia. Peripheral infection and inflammatory processes are likely to be important in this respect. Thus, it appears that inflammation may be important both before, in predisposing to a stroke, and afterwards, where it is important in the mechanisms of cerebral injury and repair. Inflammation is mediated by both molecular components, including cytokines, and cellular components, such as leukocytes and microglia, many of which possess pro- and/or antiinflammatory properties, with harmful or beneficial effects. Classic acute-phase reactants and body temperature are also modified in stroke, and may be useful in the prediction of events, outcome, and as therapeutic targets. New imaging techniques are important clinically because they facilitate dynamic evaluation of tissue damage in relation to outcome. Inflammatory conditions such as giant cell arteritis and systemic lupus erythematosus predispose to stroke, as do a range of acute and chronic infections, principally respiratory. Diverse mechanisms have been proposed to account for inflammation and infection-associated stroke, ranging from classic risk factors to disturbances of the immune and coagulation systems. Considerable opportunities therefore exist for the development of novel therapies. It seems likely that drugs currently used in the treatment of stroke, such as aspirin, statins, and modulators of the renin-angiotensin-aldosterone system, act at least partly via antiinflammatory mechanisms. Newer approaches have included antimicrobial and antileukocyte strategies. One of the most promising avenues may be the use of cytokine antagonism, for example, interleukin-1 receptor antagonist.

Chlamydia pneumoniae in atherosclerotic lesions of patients undergoing vascular surgery

The pathophysiological implications of Chlamydia pneumoniae in atherosclerotic lesions and its contribution to atherosclerotic complications remain unclear. Therefore, the purpose of the present study was to evaluate whether or not there is an association between the presence of Chlamydia pneumoniae in atherosclerotic lesions and the clinical manifestations as well as risk factors of atherosclerotic disease in patients undergoing vascular surgery. Specimens from atherosclerotic arteries were collected during endarterectomy of the carotid artery (n = 15), endarterectomy of the femoral artery (n = 19), or repair of an abdominal aortic aneurysm (n = 28). Detection of Chlamydia pneumoniae was performed by using immunohistochemical staining (IHC) with specific antibodies. Clinical manifestations of atherosclerotic disease were defined by the presence of cardiovascular risk factors, coronary heart disease, and previous vascular surgery. Inflammatory serum markers were determined in all patients prior to surgery. The specimens of all 62 patients revealed severe atherosclerosis in histological examination and a positive IHC was observed in 41 samples (66%). There were no differences regarding cardiovascular risk factors, coronary heart disease, events of previous vascular surgery, or inflammatory serum markers when comparing patients with positive and negative IHC. In conclusion, our findings showed no correlation between clinical or laboratory parameters of atherosclerosis and the presence of Chlamydia pneumoniae in atherosclerotic lesions. Therefore, Chlamydia pneumoniae appears to be a concomitant phenomenon rather than a causative principle in atherosclerosis.

Chlamydia pneumoniae and atherosclerosis: critical assessment of diagnostic methods and relevance to treatment studies

A number of studies have found that inflammation of the vessel wall plays an essential role in both the initiation and progression of atherosclerosis and erosion and fissure and the eventual rupture of plaques. Chlamydia pneumoniae is one of the infectious agents that have been investigated as possible causes of this inflammation. Initial studies of the association of C. pneumoniae and cardiovascular disease (CVD) were seroepidemiologic, and these were followed by studies in which the organism was identified in vascular tissue from patients with CVD by electron microscopy, PCR and immunocytochemical staining (ICC). C. pneumoniae has also been isolated by culture from vascular tissue in a small number patients. However, no single serologic, PCR, or ICC assay has been used consistently across all studies. The assays used are also not standardized. Recent studies of serologic and PCR assays for diagnosis of C. pneumoniae infection have suggested that there may be substantial interlaboratory variation in the performance of these tests. It now appears that some of the inconsistency of results from study to study may be due, in part, to lack of standardized methods. Although initial seroepidemiologic studies demonstrated a significantly increased risk of adverse cardiac outcome in patients who were seropositive, subsequent prospective studies found either small or no increased risk. In addition to the lack of consistent serologic criteria, recent evaluations have demonstrated inherent problems with performance of the most widely used serologic methods. Most importantly, we do not have a reliable serologic marker for chronic or persistent C. pneumoniae infection.

Determinants of carotid microembolization

PURPOSE

Earlier studies have highlighted risk factors for perioperative stroke after carotid endarterectomy, such as female sex, preoperative symptoms, and cerebral infarction. In this study, we investigated the relationship between these factors and perioperative microembolization.

METHODS

A total of 235 patients were entered in the study at two centers. Transcranial Doppler ultrasound scanning was possible in 190 patients (81%) and was performed for 1 hour preoperatively and continuously intraoperatively as a means of detecting microemboli and monitoring mean middle cerebral artery velocity. The findings of transcranial Doppler ultrasound scanning were related to perioperative risk factors by means of univariate analysis.

RESULTS

Microemboli were detected in 28 (15%), 79 (42%), and 98 (52%) patients preoperatively, during carotid artery dissection, and after closure of the artery, respectively. Having 10 or more emboli after carotid artery closure was more common in women (P = .04) and in patients with symptomatic carotid artery disease (P = .04) and was demonstrated in three of the six patients who had a perioperative stroke. These three patients also had preoperative evidence of cerebral infarction and an intraoperative middle cerebral artery velocity less than 40 cm/s.

CONCLUSION

In this study, perioperative microembolization was more common in women and patients with symptomatic carotid artery disease. These findings may explain the increased risk of carotid surgery in these patients.