Chlamydia pneumoniae serology: interlaboratory variation in microimmunofluorescence assay results

Multipeptide Assays for Sensitive and Differential Detection of Anti-Chlamydia Trachomatis Antibodies

Detection of anti-Chlamydia trachomatis (Ctr) antibodies is compromised by cross-reactivity and poor sensitivity of classic Ctr-antigens. We discovered 48 strongly reactive peptide antigens of Ctr-specific B-cell epitopes from 21 immunodominant proteins. In this study, we review the utility of peptide assays for diagnosis of Ctr infections. By combining many of these Ctr-specific B-cell epitopes from several proteins in separate or mixed multipeptide assays, they achieved vastly superior assay sensitivity and specificity over standard enzyme-linked immunosorbent assays. Such multipeptide assays eliminate cross-reactivities (false positives) and correct for stochastic gaps in antibody responses (false negatives). More importantly, we developed and validated a novel microarray platform in which hundreds of peptides from many proteins are spotted in a single reaction well. This offers the possibility of high-throughput screening of many candidate peptides for routine serological fingerprinting of Ctr infections. Discovery of optimal sets of antibody responses that associate with clinical pelvic inflammatory disease (PID) may identify diagnostically useful PID biomarker antigens.

Analysis of humoral immune responses to recombinant Chlamydia pneumoniae antigens

OBJECTIVES

Chlamydia pneumoniae is a difficult to diagnose respiratory pathogen. This study was performed to systematically characterize humoral immune responses to selected C. pneumoniae antigens in order to provide novel serodiagnostic perspectives for clinical and epidemiological issues.

METHODS

Based on a literature search, gene library screening, and serological proteome analysis, 15 immunogenic surface-associated, virulence-associated, and hypothetical C. pneumoniae antigens were selected, recombinantly expressed, and lined on a nitrocellulose strip. Specific IgM and IgG reactivity was measured in a total of 172 PCR- and micro-immunofluorescence testing (MIF)-characterized serum samples from patients with respiratory infections. A theoretical model was conceived to approximate a putative course of C. pneumoniae antigen expression and assess the potential of early and late antigens.

RESULTS

While surface antigens performed poorly, the virulence-associated TARP was a reliable antigen for IgM detection, with a sensitivity of 80.0% and a diagnostic specificity of 90.2%. The hypothetical protein YwbM proved powerful for IgG detection with MIF-correlative sensitivities of up to 94.4% and a diagnostic specificity of 95.1%.

CONCLUSIONS

This study provides new insights into antibody profiles to immunogenic proteins in C. pneumoniae infection. The study findings offer antigen candidates for more reliable and standardized serological investigations of C. pneumoniae infections, including studies on seroprevalence and epidemiology.

Multi-peptide ELISAs overcome cross-reactivity and inadequate sensitivity of conventional Chlamydia pneumoniae serology

Cross-reactivity of classical chlamydial antigens compromises Chlamydia (C.) pneumoniae serology. By testing with 185 human antisera, we expanded 18 previously discovered C. pneumoniae-specific B-cell epitopes to 48 peptide antigens from 12 C. pneumoniae immunodominant proteins. For specific detection of antibodies against C. pneumoniae, we developed novel ELISAs with strongly reactive individual peptide antigens and mixtures of these peptides. By comparison to a composite reference standard (CRS) for anti-C. pneumoniae antibody status of human sera, the top-performing CpnMixF12 peptide assay showed 91% sensitivity at 95% specificity, significantly higher than 4 commercial anti-C. pneumoniae IgG ELISAs (36-12% sensitivity at 95% specificity). Human C. pneumoniae (Cpn) and C. trachomatis (Ctr) seroreactivity was 54% biased towards co-positivity in commercial Cpn and Ctr ELISAs, but unbiased in Cpn and Ctr peptide antibody assays, suggesting severe cross-reactivity of commercial ELISAs. Using hyperimmune mouse sera against each of 11 Chlamydia spp., we confirm that commercial Cpn and Ctr ELISA antigens are cross-reactive among all Chlamydia spp., but Cpn and Ctr peptide antigens react only with antisera against the cognate chlamydial species. With simultaneously high specificity and sensitivity, and convenient use for non-specialized laboratories, these ELISAs have the potential to improve serodiagnosis of C. pneumoniae infection.

Prevalence and persistence of Chlamydia trachomatis-specific antibodies after occasional and recurrent infections

OBJECTIVES

Population-based Chlamydia trachomatis seroepidemiological studies help to identify trends in chlamydia infection. However, an improved understanding of the antibody response to infection is required when using serology to estimate cumulative incidence. Thus, the objectives of this longitudinal, retrospective, biobank-based study were to assess the appearance and persistence of C. trachomatis major outer membrane protein (MOMP)-specific serum IgG antibodies after infection and to evaluate the role of antibodies in providing protective immunity against recurrent infection.

METHODS

Data of notified C. trachomatis infections in Finland were obtained from the National Infectious Diseases Register. Serum samples were acquired from the Finnish Maternity Cohort. 411 women with single chlamydia infection and 62 women with recurrent infections, and for whom suitable paired serum samples were available, were included in the study. Antibody appearance, persistence after infection and the impact of recurrent infections were evaluated. IgG antibodies specific for MOMP were measured from serum using an ELISA method.

RESULTS

Anti-C. trachomatis MOMP-specific IgG antibodies were detected in 65.5% (269/411) of women within 3 months of notification of infection. In the absence of recurrent infection, seroprevalence declined to 34.5% (142/411) 3-10 years after the initial infection. The serum antibody levels at baseline correlated positively with seroprevalence at follow-up. Reinfection boosted the humoral immune response by increasing seroprevalence and the serum antibody levels. Seroprevalence within 3 months after first notification of infection was 65.5% (19/29) in women who were later diagnosed with recurrent infection, comparable with women with single notification of infection (65.5%, 269/411).

CONCLUSIONS

Approximately one-third of women with single notification of chlamydia infection remain seropositive 3-10 years after the initial infection. The concentration of antibodies remained stable during the follow-up. Recurrent infection boosted the humoral immune response, but reinfection occurred despite the presence of pre-existing antibodies.

Mixed Chlamydia trachomatis Peptide Antigens Provide a Specific and Sensitive Single-Well Colorimetric Enzyme-Linked Immunosorbent Assay for Detection of Human Anti-C. trachomatis Antibodies

For detection of anti-C. trachomatis antibodies by serological assays, use of classical chlamydial antigens results in high cross-reactivity and poor sensitivity. Previously, we discovered 48 strongly reactive peptide antigens of C. trachomatis-specific B-cell epitopes from 21 immunodominant proteins, and individual testing and combined scoring of 5 to 11 peptide antigens provided highly sensitive and specific detection of anti-C. trachomatis antibodies in chemiluminescent ELISAs. To simplify this method, this study established a single-well labor-saving colorimetric ELISA using a mixture of 12 strongly reactive C. trachomatis peptide antigens (Ctr Mix1) for detection of anti-C. trachomatis antibodies. This Ctr Mix1 ELISA (94% sensitivity and 98% specificity) outperformed 4 commercial ELISAs (49% to 79% sensitivity and 98% specificity). This ELISA can be easily implemented and commercialized, with convenient setup for use in nonspecialized laboratories. Thus, this mixed peptide assay with superior specificity and sensitivity will improve serodiagnosis of C. trachomatis infections.

Sensitive and specific detection of anti-Chlamydia trachomatis antibodies in standard enzyme-linked immunosorbent assays (ELISAs) is compromised by cross-reactivity and poor sensitivity of classical C. trachomatis antigens. Previously, we discovered 48 strongly reactive peptide antigens of C. trachomatis-specific B-cell epitopes from 21 immunodominant proteins. By comprehensive individual testing of 11 top-ranked peptide antigens, we found very high sensitivity and specificity for detection of anti-C. trachomatis antibodies in chemiluminescent ELISAs. The current study established a labor-saving colorimetric ELISA by using a mixture of 12 strongly reactive C. trachomatis peptide antigens (Ctr Mix1) in a single well/serum rather than assaying reactivity to each individual peptide. For performance evaluation, we used a simulated population of 212 anti-C. trachomatis antibody-positive and -negative sera from 125 women with NAAT-confirmed active C. trachomatis infection and from 87 healthy women at low risk for C. trachomatis infection. In comparison to a composite reference standard (CRS) for anti-C. trachomatis antibody status, the Ctr Mix1 IgG ELISA achieved 93.9% sensitivity, significantly superior to the 49% to 79% sensitivities of four commercial anti-C. trachomatis IgG ELISAs, and 98% specificity of all tested assays. Compared to the labor-intensive individual peptide testing, this mixed peptide ELISA retained high specificity with only marginal, ∼5% sensitivity loss. By ROC-AUC, likelihood ratio, and predictive value analyses, the Ctr Mix1 ELISA performed satisfactorily at 10% to 75% prevalence range of anti-C. trachomatis antibodies but significantly better than commercial ELISAs. Thus, the labor-saving mixed peptide colorimetric ELISA format provides simultaneously high specificity and sensitivity for detection of anti-C. trachomatis antibodies.

IMPORTANCE For detection of anti-C. trachomatis antibodies by serological assays, use of classical chlamydial antigens results in high cross-reactivity and poor sensitivity. Previously, we discovered 48 strongly reactive peptide antigens of C. trachomatis-specific B-cell epitopes from 21 immunodominant proteins, and individual testing and combined scoring of 5 to 11 peptide antigens provided highly sensitive and specific detection of anti-C. trachomatis antibodies in chemiluminescent ELISAs. To simplify this method, this study established a single-well labor-saving colorimetric ELISA using a mixture of 12 strongly reactive C. trachomatis peptide antigens (Ctr Mix1) for detection of anti-C. trachomatis antibodies. This Ctr Mix1 ELISA (94% sensitivity and 98% specificity) outperformed 4 commercial ELISAs (49% to 79% sensitivity and 98% specificity). This ELISA can be easily implemented and commercialized, with convenient setup for use in nonspecialized laboratories. Thus, this mixed peptide assay with superior specificity and sensitivity will improve serodiagnosis of C. trachomatis infections.

Discovery of Human-Specific Immunodominant Chlamydia trachomatis B Cell Epitopes

Current serological assays for species-specific detection of anti-Chlamydia species antibodies suffer from well-known shortcomings in specificity and ease of use. Due to the high prevalences of both anti-C. trachomatis and anti-C. pneumoniae antibodies in human populations, species-specific serology is unreliable. Therefore, novel specific and simple assays for chlamydial serology are urgently needed. Conventional antigens are problematic due to extensive cross-reactivity within Chlamydia spp. Using accurate B cell epitope prediction and a robust peptide ELISA methodology developed in our laboratory, we identified immunodominant C. trachomatis B cell epitopes by screening performed with sera from C. trachomatis-infected women. We discovered 38 novel human host-dependent antigens from 20 immunodominant C. trachomatis proteins, in addition to confirming 10 host-independent mouse serum peptide antigens that had been identified previously. This extended set of highly specific C. trachomatis peptide antigens can be used in simple ELISA or multiplexed microarray formats and will provide high specificity and sensitivity to human C. trachomatis serodiagnosis.

Chlamydia species-specific serology is compromised by cross-reactivity of the gold standard microimmunofluorescence (MIF) or commercial enzyme-linked immunosorbent assays (ELISAs). This study was conducted to discover novel C. trachomatis-specific peptide antigens that were recognized only by the antibody response of the natural human host. We evaluated a library of 271 peptide antigens from immunodominant C. trachomatis proteins by reactivity with 125 C. trachomatis antibody-positive sera from women with PCR-confirmed C. trachomatis infection and 17 C. trachomatis antibody-negative sera from low-risk women never diagnosed with C. trachomatis infection. These C. trachomatis peptide antigens had been predicted in silico to contain B cell epitopes but had been nonreactive with mouse hyperimmune sera against C. trachomatis. We discovered 38 novel human host-dependent antigens from 20 immunodominant C. trachomatis proteins (PmpD, IncE, IncG, CT529, CT618, CT442, TarP, CT143, CT813, CT795, CT223, PmpC, CT875, CT579, LcrE, IncA, CT226, CT694, Hsp60, and pGP3). Using these human sera, we also confirmed 10 C. trachomatis B cell epitopes from 6 immunodominant C. trachomatis proteins (OmpA, PmpD, IncE, IncG, CT529, and CT618) as host species-independent epitopes that had been previously identified by their reactivity with mouse hyperimmune sera against C. trachomatis. ELISA reactivities against these peptides correlated strongly with the C. trachomatis microimmunofluorescence (MIF) text results (Pearson’s correlation coefficient [R] = 0.80; P < 10⁻⁶). These C. trachomatis peptide antigens do not cross-react with antibodies against other Chlamydia species and are therefore suitable for species-specific detection of antibodies against C. trachomatis. This study identified an extended set of peptide antigens for simple C. trachomatis-specific ELISA serology.

IMPORTANCE Current serological assays for species-specific detection of anti-Chlamydia species antibodies suffer from well-known shortcomings in specificity and ease of use. Due to the high prevalences of both anti-C. trachomatis and anti-C. pneumoniae antibodies in human populations, species-specific serology is unreliable. Therefore, novel specific and simple assays for chlamydial serology are urgently needed. Conventional antigens are problematic due to extensive cross-reactivity within Chlamydia spp. Using accurate B cell epitope prediction and a robust peptide ELISA methodology developed in our laboratory, we identified immunodominant C. trachomatis B cell epitopes by screening performed with sera from C. trachomatis-infected women. We discovered 38 novel human host-dependent antigens from 20 immunodominant C. trachomatis proteins, in addition to confirming 10 host-independent mouse serum peptide antigens that had been identified previously. This extended set of highly specific C. trachomatis peptide antigens can be used in simple ELISA or multiplexed microarray formats and will provide high specificity and sensitivity to human C. trachomatis serodiagnosis.

Comprehensive Molecular Serology of Human Chlamydia trachomatis Infections by Peptide Enzyme-Linked Immunosorbent Assays

For detection of anti-Chlamydia trachomatis antibodies by serological assays, use of classical whole-organism chlamydial antigens results in high cross-reactivity. These antigens bind mainly antibodies against the major outer membrane protein (OmpA) and bind antibodies against other immunodominant non-OmpA proteins to a lesser extent, resulting in poor assay sensitivity. The specificity of C. trachomatis serology is also compromised by the high prevalence of cross-reactive anti-C. pneumoniae antibodies in human populations. We previously identified 48 highly specific C. trachomatis B cell epitope peptide antigens of 21 immunodominant proteins. This study validated peptide antigen-based novel ELISAs that provide highly specific and sensitive detection of anti-C. trachomatis antibodies. Compared to four commercial ELISAs that achieved only poor sensitivities (51.5% to 64.8%), the combined signals of 5 to 11 peptides provided high sensitivity (86.5% to 91.8%) at the same 98% specificity. Thus, by using multiple peptide antigens of immunodominant proteins, we created simple ELISAs with specificity and sensitivity superior to standard C. trachomatis serodiagnosis.

Sensitive species-specific detection of anti-Chlamydia trachomatis antibodies is compromised by cross-reactivity of the C. trachomatis antigens used in standard microimmunofluorescence (MIF) testing and enzyme-linked immunosorbent assays (ELISAs). Previously, we discovered 48 strongly reactive C. trachomatis-specific B cell epitope peptides from 21 immunodominant proteins. Here we comprehensively evaluated the 11 top-ranked C. trachomatis-specific peptide antigens from 8 proteins for use in C. trachomatis serology. Sera from 125 women with nucleic acid amplification test (NAAT)-confirmed active C. trachomatis infection and from 49 healthy women with a low risk of C. trachomatis infection were used as anti-C. trachomatis antibody-positive and -negative sera. Results obtained for detection of IgG1, IgG3, and IgA1 antibodies against the 11 C. trachomatis peptide antigens were compared to results from 4 commercial anti-C. trachomatis IgG ELISAs. Using composite reference standards (CRS) of all assays for anti-C. trachomatis antibody status, commercial ELISAs detected antibodies in antibody-positive women with sensitivities of 51.5% to 64.8%. In contrast, a combination of the results of all 11 peptides detected IgG (IgG1 and IgG3) antibodies with 91.8% sensitivity, and a labor-saving combination of the 5 optimal peptides still detected antibodies in antibody-positive women with 86.5% sensitivity (all at 98% specificity). The superior performance of the combined peptide ELISAs was confirmed by area under the receiver operating characteristic curve (ROC-AUC), likelihood ratio, and predictive value analyses. The higher sensitivity of the peptide assays results from using multiple B cell epitopes of several C. trachomatis immunodominant proteins, including OmpA, compared to exclusively using the OmpA antigens used in commercial ELISAs. Thus, ELISAs with combined use of synthetic peptide antigens for C. trachomatis antibody detection have the advantage of simultaneous high sensitivity and high specificity.

IMPORTANCE For detection of anti-Chlamydia trachomatis antibodies by serological assays, use of classical whole-organism chlamydial antigens results in high cross-reactivity. These antigens bind mainly antibodies against the major outer membrane protein (OmpA) and bind antibodies against other immunodominant non-OmpA proteins to a lesser extent, resulting in poor assay sensitivity. The specificity of C. trachomatis serology is also compromised by the high prevalence of cross-reactive anti-C. pneumoniae antibodies in human populations. We previously identified 48 highly specific C. trachomatis B cell epitope peptide antigens of 21 immunodominant proteins. This study validated peptide antigen-based novel ELISAs that provide highly specific and sensitive detection of anti-C. trachomatis antibodies. Compared to four commercial ELISAs that achieved only poor sensitivities (51.5% to 64.8%), the combined signals of 5 to 11 peptides provided high sensitivity (86.5% to 91.8%) at the same 98% specificity. Thus, by using multiple peptide antigens of immunodominant proteins, we created simple ELISAs with specificity and sensitivity superior to standard C. trachomatis serodiagnosis.

Association of Chlamydia pneumoniae immunoglobulin G antibodies with the risk of lung cancer among non-smoking women in Liaoning, China

The role of Chlamydia pneumoniae in the cause of lung cancer is controversial. In this study, we investigated the association between C. pneumoniae immunoglobulin (Ig) G antibodies and risk of lung cancer among non-smoking women. C. pneumoniae IgG antibody levels were compared between 192 adult Chinese women who met the diagnostic criteria of lung cancer and 90 healthy controls. C. pneumoniae IgG antibodies were tested with the use of an enzyme-linked immunosorbent assay. The prevalence of C. pneumoniae IgG seropositivity was 61.98% of cases and 28.89% of controls (P < 0.05). According to the results of the multiple logistic analysis model, the odds ratios for C. pneumoniae IgG antibody seropositivity, body mass index, and educational levels were 3.919 (P < 0.001), 0.731 (P= 0.274), and 1.646 (P= 0.069), respectively. C. pneumoniae infection may be a risk factor for lung cancer.

Automated Image Analysis for Determination of Antibody Titers Against Occupational Bacterial Antigens Using Indirect Immunofluorescence

Employees who are exposed to high concentrations of microorganisms in bioaerosols frequently suffer from respiratory disorders. However, etiology and in particular potential roles of microorganisms in pathogenesis still need to be elucidated. Thus, determination of employees' antibody titers against specific occupational microbial antigens may lead to identification of potentially harmful species. Since indirect immunofluorescence (IIF) is easy to implement, we used this technique to analyze immunoreactions in human sera. In order to address disadvantageous inter-observer variations as well as the absence of quantifiable fluorescence data in conventional titer determination by eye, we specifically developed a software tool for automated image analysis. The 'Fluorolyzer' software is able to reliably quantify fluorescence intensities of antibody-bound bacterial cells on digital images. Subsequently, fluorescence values of single cells have been used to calculate non-discrete IgG titers. We tested this approach on multiple bacterial workplace isolates and determined titers in sera from 20 volunteers. Furthermore, we compared image-based results with the conventional manual readout and found significant correlation as well as statistically confirmed reproducibility. In conclusion, we successfully employed 'Fluorolyzer' for determination of titers against various bacterial species and demonstrated its applicability as a useful tool for reliable and efficient analysis of immune response toward occupational exposure to bioaerosols.

Background review for the '2015 European guideline on the management of Chlamydia trachomatis infections'

SummaryChlamydia trachomatis infections are major public health concerns globally. Of particular grave concern is that the majority of persons with anogenital Chlamydia trachomatis infections are asymptomatic and accordingly not aware of their infection, and this silent infection can subsequently result in severe reproductive tract complications and sequelae. The current review paper provides all background, evidence base and discussions for the 2015 European guideline on the management of Chlamydia trachomatis infections (Lanjouw E, et al. Int J STD AIDS 2015). Comprehensive information and recommendations are included regarding the diagnosis, treatment and prevention of anogenital, pharyngeal and conjunctival Chlamydia trachomatis infections in European countries. However, Chlamydia trachomatis also causes the eye infection trachoma, which is not a sexually transmitted infection. The 2015 European Chlamydia trachomatis guideline provides up-to-date guidance regarding broader indications for testing and treatment of Chlamydia trachomatis infections; clearer recommendation of using validated nucleic acid amplification tests only for diagnosis; advice on (repeated) Chlamydia trachomatis testing; recommendation of increased testing to reduce the incidence of pelvic inflammatory disease and prevent exposure to infection and recommendations to identify, verify and report Chlamydia trachomatis variants. Improvement of access to testing, test performance, diagnostics, antimicrobial treatment and follow-up of Chlamydia trachomatis patients are crucial to control its spread.

Laboratory diagnosis of persistent human chlamydial infection

Diagnostic assays for persistent chlamydial infection are much needed to conduct high-quality, large-scale studies investigating the persistent state in vivo, its disease associations and the response to therapy. Yet in most studies the distinction between acute and persistent infection is based on the interpretation of the data obtained by the assays developed to diagnose acute infections or on complex assays available for research only and/or difficult to establish for clinical use. Novel biomarkers for detection of persistent chlamydial infection are urgently needed. Chlamydial whole genome proteome arrays are now available and they can identify chlamydial antigens that are differentially expressed between acute infection and persistent infection. Utilizing these data will lead to the development of novel diagnostic assays. Carefully selected specimens from well-studied patient populations are clearly needed in the process of translating the proteomic data into assays useful for clinical practice. Before such antigens are identified and validated assays become available, we face a challenge of deciding whether the persistent infection truly induced appearance of the proposed marker or do we just base our diagnosis of persistent infection on the presence of the suggested markers. Consequently, we must bear this in mind when interpreting the available data.

A review of serological tests to assist diagnosis of reactive arthritis: critical appraisal on methodologies

On a population-based level, the incidence of reactive arthritis (ReA) is 0.6–27/100,000. The definition of ReA varies and its pathogenesis is not yet clear. Attempts in basic immunology to suggest hypotheses for proliferation of forbidden B cell clones, molecular mimicry, and involvement of cross-reactive antibodies are helpful but not sufficient. Importantly, for the clinical diagnosis of the preceding infection, serology is widely used. Unfortunately, the accuracy of associations between serologic findings and clinical conclusions is plagued by poor standardization of methods. So far, few attempts have been done to examine the pitfalls of different approaches. Here, we review several serologic techniques, their performance and limitations. We will focus on serology for Yersinia, Campylobacter, Salmonella, Shigella, and Chlamydia trachomatis because these bacteria have a longer history of being associated with ReA. We also address controversies regarding the role of serology for some other bacteria linked to autoimmune disorders.

Effect of time since exposure to Chlamydia trachomatis on chlamydia antibody detection in women: a cross-sectional study

OBJECTIVES

To investigate what factors influence the detection of Chlamydia trachomatis antibody following genital tract infection.

METHODS

One hundred and sixty-four women with a previous history of C trachomatis infection contributed to an earlier report on the performance of chlamydia antibody ELISA assays. We undertook further analysis to explore how chlamydia antibody assay sensitivity changes with time since infection.

RESULTS

Chlamydia antibody was detected in more women soon after the last detection of chlamydia at the lower genital tract than at later times. This holds true for all tests, but the Anilabsystems IgG EIA, Medac pELISA plus ELISA and the Savyon SeroCT-IgG ELISA were less sensitive than the pgp3 ELISA and the Anilabsystems microimmunofluorescence (MIF) assay at all time points except during current infection. Fall in seropositivity in women generally occurred in the early weeks and months following the last episode of chlamydia infection. There was no clear pattern of further reduction in seropositivity after 6 months. Multiple previous episodes were associated with increased seropositivity in the pgp3 assay (two or more vs one, OR 19, p<0.001) and other tests, but the effect was significantly smaller for the Anilabs, Medac and SeroCT MOMP peptide ELISAs, but not for the MIF assay.

CONCLUSIONS

Chlamydia antibody detection decreases with time since infection and this is most apparent in the first 6 months. In women who have had more than one infection, antibody remained detectable longer for all tests, but this was more marked for the pgp3 ELISA and MIF assay.

Serological diagnosis of Chlamydia pneumoniae infection: limitations and perspectives

Chlamydia pneumoniae is an obligate intracellular human pathogen responsible for a wide range of acute and chronic human diseases, including pneumonia and other respiratory diseases. Serological methods for the diagnosis of C. pneumoniae infection vary widely, and several authors have reported significant inter- and intra-laboratory variability in diagnostic methods and criteria. Over the past 10 years, numerous studies have focused on the identification of specific antigens for application in serodiagnosis, including the diagnosis of persistent infections. The use of proteomics may enable the development of serological diagnosis kits that offer reliable sensitivity and specificity and might even differentiate between the various stages of infection with this pathogen.

Combination antibiotics as a treatment for chronic Chlamydia-induced reactive arthritis: a double-blind, placebo-controlled, prospective trial

OBJECTIVE

Chlamydia trachomatis and Chlamydophila (Chlamydia) pneumoniae are known triggers of reactive arthritis (ReA) and exist in a persistent metabolically active infection state in the synovium, suggesting that they may be susceptible to antimicrobial agents. The goal of this study was to investigate whether a 6-month course of combination antibiotics is an effective treatment for patients with chronic Chlamydia-induced ReA.

METHODS

This study was a 9-month, prospective, double-blind, triple-placebo trial assessing a 6-month course of combination antibiotics as a treatment for Chlamydia-induced ReA. Eligible patients had to be positive for C trachomatis or C pneumoniae by polymerase chain reaction (PCR). Groups received 1) doxycycline and rifampin plus placebo instead of azithromycin; 2) azithromycin and rifampin plus placebo instead of doxycycline; or 3) placebos instead of azithromycin, doxycycline, and rifampin. The primary end point was the number of patients who improved by 20% or more in at least 4 of 6 variables without worsening in any 1 variable in both combination antibiotic groups combined and in the placebo group at month 6 compared with baseline.

RESULTS

The primary end point was achieved in 17 of 27 patients (63%) receiving combination antibiotics and in 3 of 15 patients (20%) receiving placebo. Secondary efficacy end points showed similar results. Six of 27 patients (22%) randomized to combination antibiotics believed that their disease went into complete remission during the trial, whereas no patient in the placebo arm achieved remission. Significantly more patients in the active treatment group became negative for C trachomatis or C pneumoniae by PCR at month 6. Adverse events were mild, with no significant differences between the groups.

CONCLUSION

These data suggest that a 6-month course of combination antibiotics is an effective treatment for chronic Chlamydia-induced ReA.

Chlamydophila pneumoniae

Chlamydophila pneumoniae is estimated to cause about 10% of community-acquired pneumonia (CAP) cases and 5% of bronchitis cases, although most patients with C pneumoniae infection are asymptomatic, and the course of respiratory illness is relatively mild. The incubation period of C pneumoniae infection is around 21 days, and such symptoms as cough and malaise show a gradual onset, yet may persist for several weeks or months despite appropriate antibiotic therapy. Diagnosis by nasopharyngeal specimen culture, serum antibody titers, or molecular techniques is usually delayed with respect to the onset of symptoms, antibiotic treatment, or disease resolution and there is no accurate, standardized, commercial US Food and Drug Administration-cleared diagnostic method available. Erythromycin, tetracycline, and doxycycline are used as first-line therapy, although some investigators report no clinical or survival benefits from treating CAP caused by atypical pathogens. Meanwhile, adequate prospective studies have met with ethical and logistic barriers. Despite these limitations, North American guidelines recommend the antimicrobial treatment of patients with acute C pneumoniae respiratory infection.

Chlamydophila pneumoniae Infection and Its Role in Neurological Disorders

Chlamydophila pneumoniae is an intracellular pathogen responsible for a number of different acute and chronic infections. The recent deepening of knowledge on the biology and the use of increasingly more sensitive and specific molecular techniques has allowed demonstration of C. pneumoniae in a large number of persons suffering from different diseases including cardiovascular (atherosclerosis and stroke) and central nervous system (CNS) disorders. Despite this, many important issues remain unanswered with regard to the role that C. pneumoniae may play in initiating atheroma or in the progression of the disease. A growing body of evidence concerns the involvement of this pathogen in chronic neurological disorders and particularly in Alzheimer's disease (AD) and Multiple Sclerosis (MS). Monocytes may traffic C. pneumoniae across the blood-brain-barrier, shed the organism in the CNS and induce neuroinflammation. The demonstration of C. pneumoniae by histopathological, molecular and culture techniques in the late-onset AD dementia has suggested a relationship between CNS infection with C. pneumoniae and the AD neuropathogenesis. In particular subsets of MS patients, C. pneumoniae could induce a chronic persistent brain infection acting as a cofactor in the development of the disease. The role of Chlamydia in the pathogenesis of mental or neurobehavioral disorders including schizophrenia and autism is uncertain and fragmentary and will require further confirmation.

Chlamydia pneumoniae infection is associated with elevated body mass index in young men

Chlamydia pneumoniae infection is said to be associated with obesity. We studied the association between C. pneumoniae infection and inflammation and increased BMI in 891 Finnish military recruits. IgG seropositivity in arrival and departure serum samples during 6-12 months of military service was considered as persistence of antibodies and a possible indication of chronic infection. Persistently high C-reactive protein (CRP) level (elevated on arrival and departure) (OR 2.2, 95% CI 1.3-3.9), and persistent C. pneumoniae antibodies (OR 2.1, 95% CI 1.5-2.8) were significant risk factors for overweight (BMI 25 kg/m2). In addition, those who had persistent antibodies and persistently elevated CRP levels, or those who had either of them, had a significantly higher BMI (kg/m2) compared to those who had neither of them (25.8 vs. 24.6 vs. 23.5, respectively; P<0.001). These results provide new information about the association between possible chronic C. pneumoniae infection and obesity in young men.

Chlamydial infection: the link with ocular adnexal lymphomas

Chlamydiae are obligate intracellular bacteria that grow in eukaryotic cells and cause a wide spectrum of diseases. They can establish persistent infections, are mitogenic in vitro, promote polyclonal cell proliferation in vivo and induce resistance to apoptosis in infected cells-properties that might contribute to tumorigenesis. In fact, Chlamydophila psittaci (Cp) has been linked to the development and maintenance of ocular adnexal marginal zone B-cell lymphoma (OAMZL). In this indolent malignancy, Cp is transported by monocytes and macrophages and causes both local and systemic infection. Cp elementary bodies are viable and infectious in the conjunctiva and peripheral blood of patients with OAMZL. Bacterial eradication with antibiotic therapy is often followed by lymphoma regression. Despite recent advances in the understanding of this bacterium-lymphoma association, several questions remain unanswered. For instance, prevalence variations among different geographical areas and related diagnostic and therapeutic implications remain a major investigational issue. We will focus on clinical and therapeutic implications of chlamydial infections in patients with lymphomas and summarize the current knowledge on the association between Cp infection and OAMZL. Available data on the epidemiology, biology and pathogenesis of this association are analyzed and new investigative and clinical approaches are discussed.

Chlamydophila pneumoniae infection and COPD: more evidence for lack of evidence?

Chlamydophila pneumoniae has been recognized as a common cause of respiratory tract infections affecting all age groups. The organism has been implicated as an infectious trigger for acute exacerbations of COPD. Moreover, the intracellular existence of this pathogen and the ability to cause chronic respiratory infections have led to a number of studies that investigated its possible association with disease development. The present paper examines and discusses the possible association of acute C. pneumoniae infection in episodes of acute exacerbation of COPD. It also reviews the existing evidence of chronic C. pneumoniae infection with disease pathogenesis and severity. The significant interstudy variation of the choice of diagnostic methods and criteria applied is most likely responsible for the great diversity of results observed. The use of well-standardized, commercially available diagnostic tools, as well as the adoption of a more unified diagnostic approach is probably the key element missing in order to clarify the exact role of C. pneumoniae in COPD.

Infectious Risk Factors for Atherosclerotic Vascular Disease in Hemodialysis Patients—Chlamydia pneumoniaebut notHelicobacter pylorior Cytomegalovirus is Associated with Increased C‐Reactive Protein

BACKGROUND

Cardiovascular disease is a major problem in patients with chronic renal failure leading to increased mortality. Several infectious agents have been implicated to be associated with atherosclerosis. We were interested to evaluate whether there is a correlation between a past infection with Chlamydia pneumoniae (Cpn), Helicobacter pylori (Hp) or cytomegalovirus (CMV) and the manifestation of a symptomatic atherosclerotic disease in patients with endstage renal failure.

METHODS AND RESULTS

Patients (n=267) on hemodialysis were investigated. In 101 patients with an apparent atherosclerotic disease (case group) increased IgA levels against Cpn were found (p < or = 0.0001 vs. controls; n=33). Nearly 45% of the case group had a history of myocardial infarction (MI) (p < or = 0.0001). Prior stroke was found in about 30% of patients in the case group (p < or = 0.002). Elevated CRP levels were identified as an independent risk factor for atherosclerosis in all groups. IgA seropositivity against Cpn correlated with elevated CRP values for all atherosclerotic patients (p < or = 0.001), especially in the group of patients with MI (p < or = 0.019) and peripheral vascular disease (p < or = 0.005). There was no correlation between CMV (IgG, IgM) or Hp (IgA, IgG) seropositivity and atherosclerotic disease.

CONCLUSION

IgA seropositivity for Cpn and elevated CRP values but not Hp or CMV was associated with an increased rate of symptomatic atherosclerotic manifestations as MI, stroke, cerebral or peripheral atherosclerosis in patients with endstage renal disease on hemodialysis.

Prevalence of Chlamydophila psittaci infections in a human population in contact with domestic and companion birds

Chlamydophila psittaci infections in humans are underestimated. We investigated the occurrence of C. psittaci in a Belgian population of 540 individuals. Data were from a population survey (n=2524) of apparently healthy community-dwelling subjects aged 35-55 years. Pharyngeal swabs and blood were taken. Individuals completed a questionnaire on professional and nonprofessional activities, smoking habits, medical history and contact frequency with different bird species. Swabs were analysed by a C. psittaci-specific and a Chlamydophila pneumoniae-specific PCR. Sera were tested by a recombinant C. psittaci major outer-membrane protein-based ELISA, a C. psittaci whole organism-based ELISA (Serion) and a micro-immunofluorescence test (Focus Diagnostics). Results confirmed our suspicion about the underestimation of psittacosis in Belgium. Psittaciformes and racing pigeons were the main infection source. Women with excessive alcohol intake defined as a mean intake of >2 units daily were more frequently infected than men. We analysed the effect of seropositivity and/or PCR positivity on inflammation (white blood cell count, high-sensitivity C-reactive protein, fibrinogen). In general, seropositivity showed a trend to slightly higher levels of inflammatory variables (all non-significant), whilst PCR positivity showed a trend to no effect or even lower inflammatory levels.

Multiplexed whole bacterial antigen microarray, a new format for the automation of serodiagnosis: the culture-negative endocarditis paradigm

The serological diagnosis of blood culture-negative endocarditis due to Coxiella burnetii, Bartonella spp., Brucella melitensis and Legionella pneumophila is based on a manual immunofluorescence assay (IFA), which is taken to be the reference method. The automated IFA InoDiag multiplexed antigenic microarray, which includes a slide with all the above bacteria and four internal controls, an incubator, a fluorescent reader and software with an algorithm of interpretation for infectious endocarditis (IE) was evaluated. A single serum dilution at 1/128 was used. Eleven patients with Bartonella spp. IE and ten with C. burnetii IE, diagnosed using the modified Duke criteria, as well as one patient with B. melitensis infection and three patients with L. pneumophila IE were tested. In total, 236 sera were used as negative controls, with the reference method. The results of IgG detection were: C. burnetii phase I, 'sensitivity (Se) = 88% and specificity (Sp) = 99%', and C. burnetii phase II, Se = 88% and Sp = 99%; for Bartonella henselae, Se = 100% and Sp = 100%; for Bartonella quintana, Se = 78% and Sp = 96%; for B. melitensis, Se = 100% and Sp = 99%; and for L. pneumophila, Se = 100% and Sp = 99%. With the algorithm interpretation, the negative and positive predictive values of the test 'were 100% for the diagnosis of IE caused by the four bacteria tested. These results were confirmed by two other assays, one using triplicate testing and one blind testing performed by another centre. This multiplexed test is therefore a valuable tool for the rapid diagnosis of blood-culture negative IE.

Comparison of the new InoDiag automated fluorescence multiplexed antigen microarray to the reference technique in the serodiagnosis of atypical bacterial pneumonia

The aetiological diagnosis of pneumonia depends largely on culture-, antigen- or PCR-based tests. Atypical agents of pneumonia include Coxiella burnetii, Chlamydophila pneumoniae, Chlamydia psittaci, Legionella pneumophila, Francisella tularensis and Mycoplasma pneumoniae. In these cases, serological tests are commonly used for diagnosis. All of the above species were comparatively screened for by using the InoDiag multiplexed automatic immunofluorescence assay and established reference techniques. The InoDiag assay required 5 microL of serum, took 76 min per serum sample, and required an incubator, a fluorescence reader and interpretation software. In total, 248 single sera from patients were tested, for the diagnosis of pneumonia, and the results obtained with selected serum samples were compared with results obtained with the reference method. It was shown that, for the detection of Coxiella burnetii IgM, the automated assay had a sensitivity and specificity of 100%. For the detection of M. pneumoniae IgM, sensitivity was 100% and specificity was 98%. For the detection of Chlamydophila pneumoniae and Chlamydia psittaci IgG, sensitivity was 81% and specificity was 94%. For the detection of L. pneumoniae IgG, sensitivity was 63% and specificity was 98%. For the detection of F. tularensis IgG and IgM, sensitivity was 100% for both, and specificity was 95% and 100%, respectively. The performance of this serological assay was comparable to that of other assays reported in the literature. This preliminary study shows that the automatic InoDiag assay opens the way to immunofluorescence assay standardization.

Evaluation and optimization of a commercial enzyme linked immunosorbent assay for detection of Chlamydophila pneumoniae IgA antibodies

BACKGROUND

Serologic diagnosis of Chlamydophila pneumoniae (Cpn) infection routinely involves assays for the presence of IgG and IgM antibodies to Cpn. Although IgA antibodies to Cpn have been found to be of interest in the diagnosis of chronic infections, their significance in serological diagnosis remains unclear. The microimmunofluorescence (MIF) test is the current method for the measurement of Cpn antibodies. While commercial enzyme linked immunosorbent assays (ELISA) have been developed, they have not been fully validated. We therefore evaluated and optimized a commercial ELISA kit, the SeroCP IgA test, for the detection of Cpn IgA antibodies.

METHODS

Serum samples from 94 patients with anti-Cpn IgG titers > or = 256 (study group) and from 100 healthy blood donors (control group) were tested for the presence of IgA antibodies to Cpn, using our in-house MIF test and the SeroCP IgA test. Two graph receiver operating characteristic (TG-ROC) curves were created to optimize the cut off given by the manufacturer.

RESULTS

The MIF and SeroCP IgA tests detected Cpn IgA antibodies in 72% and 89%, respectively, of sera from the study group, and in 9% and 35%, respectively, of sera from the control group. Using the MIF test as the reference method and the cut-off value of the ELISA test specified by the manufacturer for seropositivity and negativity, the two tests correlated in 76% of the samples, with an agreement of K = 0.54. When we applied the optimized cut-off value using TG-ROC analysis, 1.65, we observed better concordance (86%) and agreement (0.72) between the MIF and SeroCP IgA tests.

CONCLUSION

Use of TG-ROC analysis may help standardize and optimize ELISAs, which are simpler, more objective and less time consuming than the MIF test. Standardization and optimization of commercial ELISA kits may result in better performance.

Role of respiratory pathogens in infants hospitalized for a first episode of wheezing and their impact on recurrences

In order to evaluate the infectious agents associated with the first episode of severe acute wheezing in otherwise healthy infants and to define the role of each of them in recurrences, 85 patients in Italy, aged <12 months, hospitalized because of a first acute episode of wheezing, were prospectively enrolled between 1 October 2005 and 31 March 2006. Upon enrollment, nasopharyngeal swabs were collected for the real-time PCR detection of respiratory syncytial virus (RSV) types A and B, influenza virus types A and B, adenovirus, parainfluenza viruses types 1, 2, 3 and 4, rhinovirus, human metapneumovirus, human coronavirus types 229E, OC43, NL63, and HKU1, bocavirus, enterovirus, and paraechovirus; nasopharyngeal aspirates were also obtained to detect atypical bacteria. At least one infectious agent was identified in 76 children (89.4%). RSV was the most frequently detected pathogen and its prevalence was significantly higher than that of the other pathogens in both age groups, and significantly higher in the children aged 3-12 months than in those aged <3 months. Only the children with RSV infection experienced recurrent wheezing. Viral load was significantly higher in children with than in those without recurrent wheezing. This study shows that RSV is the main reason for hospitalization during the first wheezing episode in infants, and that it appears to be the only pathogen associated with a high frequency of recurrences. A high viral load seems to be strictly related to the likelihood of recurrence.

Increased infiltration of Chlamydophila pneumoniae in the vessel wall of human veins after perfusion

BACKGROUND

Several studies have suggested an association between Chlamydophila pneumoniae (Cp) infection and atherosclerosis. A recent study detected Cp DNA in the saphenous vein of 12% of all patients before bypass grafting and in 38% of failed grafts. We used a system in which human veins were perfused with autologous blood under arterial pressure.

MATERIALS AND METHODS

Veins were surplus segments of saphenous veins of coronary artery bypass grafting (CABG) patients. Vein grafts were perfused with the blood of the same patient after CABG procedures. Veins were analysed for Cp-specific membrane protein using immunohistochemical and PCR analysis. Veins were analysed before and after perfusion (up to 4 h). The number of Cp positive cells was then quantified in the vein layers.

RESULTS

Cp protein was detected within macrophages only. In non-perfused veins, Cp was present in the adventitia in 91% of all patients, in the circular (64%) and longitudinal (23%) layer of the media. No positivity was found in the intima. Perfusion subsequently resulted in a significant increase of Cp positive cells within the circular layer of the media that, however, differed strongly between different patients. Cp DNA was not detected by PCR in those specimens.

CONCLUSION

Cp protein was present in 91% of veins, but the number of positive cells differed remarkably between patients. Perfusion of veins resulted in increased infiltration of Cp into the circular layer. These results may point to a putative discriminating role of Cp with respect to graft failure between different patients.

Immunoproteomic identification and serological responses to novel Chlamydia pneumoniae antigens that are associated with persistent C. pneumoniae infections

The controversial discussion about the role of Chlamydia pneumoniae in atherosclerosis cannot be solved without a reliable diagnosis that allows discrimination between past and persistent infections. Using a proteomic approach and immunoblotting with human sera, we identified 31 major C. pneumoniae Ags originating from 27 different C. pneumoniae proteins. More than half of the proteins represent Chlamydia Ags not described previously. Using a comparative analysis of spot reactivity Pmp6, OMP2, GroEL, DnaK, RpoA, EF-Tu, as well as CpB0704 and CpB0837, were found to be immunodominant. The comparison of Ab-response patterns of sera from subjects with and without evidence for persisting C. pneumoniae, determined by multiple PCR analysis of PBMC and vasculatory samples, resulted in differential reactivity for 12 proteins, which is not reflected by reactivity of the sera in the microimmunofluorescence test, the current gold standard for serodiagnosis. Although reactivity of sera from PCR-positive donors was increased toward RpoA, MOMP, YscC, Pmp10, PorB, Pmp21, GroEL, and Cpaf, the reactivity toward YscL, Rho, LCrE, and CpB0837 was decreased, reflecting the altered protein expression of persisting C. pneumoniae in vitro. Our data provide the first evidence of a unique Ab-response pattern associated with persistent C. pneumoniae infections, which is a prerequisite for the serological determination of persistently infected patients.

Role of Chlamydia pneumoniae in atherosclerosis

Cardiovascular disease, resulting from atherosclerosis, is a leading cause of global morbidity and mortality. Genetic predisposition and classical environmental risk factors explain much of the attributable risk for cardiovascular events in populations, but other risk factors for the development and progression of atherosclerosis, which can be identified and modified, may be important therapeutic targets. Infectious agents, such as Chlamydia pneumoniae, have been proposed as contributory factors in the pathogenesis of atherosclerosis. In the present review, we consider the experimental evidence that has accumulated over the last 20 years evaluating the role of C. pneumoniae in atherosclerosis and suggest areas for future research in this field.

Endothelial cells are protected against phagocyte-transmitted Chlamydophila pneumoniae infections by laminar shear stress Gueinzius: Shear stress protects from C. pneumoniae infection

The respiratory pathogen Chlamydophila pneumoniae can be detected in atherosclerotic vessels, but the mechanism of dissemination from lung to vasculature remains unknown. Disturbance of vascular shear stress is a risk factor for atherosclerosis. We investigated whether polymorphonuclear neutrophils (PMN) might serve as carriers, transmitting C. pneumoniae to endothelial cells and how this is affected by shear stress. PMN were prepared from blood and incubated with C. pneumoniae. Real-time PCR and Pathfinder staining showed that after 1h, 20% of C. pneumoniae were ingested and started to form inclusions. When infected PMN were co-incubated with HUVEC for 96h, 10% of PMN-ingested C. pneumoniae were transmitted to HUVEC as shown by PCR and confocal microscopy. Infection of HEp-2 cells with C. pneumoniae harvested from HUVEC resulted in C. pneumoniae replication and confirmed that the bacteria remained infective. Exposure to laminar shear stress in a rotating cone-and-plate apparatus did not affect the transmission of C. pneumoniae from PMN to HUVEC, but led to a 75% reduction of inclusion formation. This can explain the focal distribution of C. pneumoniae in the vasculature and links two risk factors of atherosclerosis, i.e. the lack of laminar flow and infection.

Is serological testing a reliable tool in laboratory diagnosis of syphilis? Meta-analysis of eight external quality control surveys performed by the german infection serology proficiency testing program

The accuracy of diagnostic tests is critical for successful control of epidemic outbreaks of syphilis. The reliability of syphilis serology in the nonspecialist laboratory has always been questioned, but actual data dealing with this issue are sparse. Here, the results of eight proficiency testing sentinel surveys for diagnostic laboratories in Germany between 2000 and 2003 were analyzed. Screening tests such as Treponema pallidum hemagglutination assay (mean accuracy, 91.4% [qualitative], 75.4% [quantitative]), Treponema pallidum particle agglutination assay (mean accuracy, 98.1% [qualitative], 82.9% [quantitative]), and enzyme-linked immunosorbent assays (ELISAs) (mean qualitative accuracy, 95%) were more reliable than Venereal Disease Research Laboratory (VDRL) testing (mean accuracy, 89.6% [qualitative], 71.1% [quantitative]), the fluorescent treponemal antibody absorption test (FTA-ABS) (mean accuracy, 88% [qualitative], 65.8% [quantitative]), and immunoblot assays (mean qualitative accuracy, 87.3%). Clearly, immunoglobulin M (IgM) tests were more difficult to manage than IgG tests. False-negative results for samples that have been unambiguously determined to be IgM and anti-lipoid antibody positive accounted for 4.7% of results in the IgM ELISA, 6.9% in the VDRL test, 18.5% in the IgM FTA-ABS, and 23.0% in the IgM immunoblot assay. For negative samples, the mean percentage of false-positive results was 4.1% in the VDRL test, 5.4% in the IgM ELISA, 0.7% in the IgM FTA-ABS, and 1.4% in the IgM immunoblot assay. On average, 18.3% of participants misclassified samples from patients with active syphilis as past infection without indicating the need for further treatment. Moreover, 10.2% of laboratories wrongly reported serological evidence for active infection in samples from patients with past syphilis or in sera from seronegative blood donors. Consequently, the continuous participation of laboratories in proficiency testing and further standardization of tests is strongly recommended to achieve better quality of syphilis serology.

Chlamydia pneumoniae antibody levels before coronary events in the Helsinki Heart Study as measured by different methods

The lack of specific tests for the diagnosis of chronic Chlamydia pneumoniae infection has led to the use of enzyme immunoassay (EIA) instead of the gold standard, that is, microimmunofluorescence (MIF), in the measurement of C. pneumoniae antibodies. We assessed the predictive values of C. pneumoniae antibody levels and seroconversions measured by MIF and EIA for coronary events in the prospective Helsinki Heart Study. Sera from 239 cases with coronary events and 239 controls were available at the baseline and data from 210 cases and 211 controls before and after the event. The agreement between MIF and EIA antibody levels was best in high antibody titers. In conditional logistic regression analysis, only high IgA MIF titers (>/=40) at the baseline predicted future coronary events, and the participants with MIF seroconversion between consecutive sera had a higher (nonsignificant) risk for coronary events than the controls. The difference in the kinetics of EIA and MIF antibodies demonstrated that MIF should remain the gold standard.

Low prevalence of Chlamydia pneumoniae in adults with community-acquired pneumonia

The incidence of community-acquired pneumonia (CAP) due to Chlamydia pneumoniae was determined in a prospective study of 546 adult patients with CAP included in the German CAP Competence Network (CAPNETZ) project. Three different PCR protocols for detection of C. pneumoniae in respiratory specimens were compared by a multicenter, inter-laboratory comparison involving three laboratories. A case was defined as a patient with a respiratory sample positive by PCR in at least two laboratories. CAP was caused by C. pneumoniae in 5/546 cases (0.9%). Antibody testing by microimmunofluorescence was done in 376 of 546 patients. All patients were negative for IgM antibodies. In the five PCR-positive patients, neither specific IgG nor IgA antibodies were found. Patients with CAP caused by C. pneumoniae had a lower median age (36 years) than the general study population (62 years). C. pneumoniae is currently a rare cause of CAP in adult patients in Germany. Analysis of a single serum sample is not useful for diagnosis of acute C. pneumoniae infection in CAP.

Community epidemiology of Chlamydia and Mycoplasma pneumoniae in LRTI in France over 29 months

BACKGROUND

The role of Chlamydia pneumoniae (CP) and Mycoplasma pneumoniae (MP) in lower respiratory tract infections (LRTI) is still little known in community settings.

METHODS

In all, 3207 adult cases of LRTI (871 with pneumonia, and 2336 with acute bronchitis) were prospectively included in the ETIIC1 ETIIC : ETude de l'Incidence des Infections respiratoires basses d'origine Communautaire dues A Chlamydia pneumoniae et Mycoplasma pneumoniae (Incidence of CP and MP in LRTI in community settings) program by 303 general practitioners and 24 hospital physicians in France between September 1997 and February 2000. The polymerase chain reaction and immunoassays were used to detect CP or MP in 3198 pharyngeal specimens obtained by gargling.

RESULTS

Of these 3198 patients, 232 (7.3%), were PCR-positive for CP and/or MP. Immunoassays were far less sensitive than PCRs (Se = 2 and 13% for MP and CP). Among the 2336 patients with acute bronchitis, PCR was positive for CP in 95 (4.1%), and for MP, in 54 (2.3%). Among the 671 patients with radiologically confirmed pneumonia, PCR was positive for CP in 23 (3.4%), and for MP in 49 (7.3%). CP and MP displayed significant geographic heterogeneity. Independent clinical determinants of positive PCR for CP and/or MP were age below 45 years, previous antimicrobial therapy (especially betalactams). Clinical signs were not of practical use in distinguishing accurately between etiologic diagnoses.

CONCLUSIONS

CP or MP diagnosed by PCR were found in more than 7% of patients with LRTI in community settings with a significant geographical heterogeneity and significant temporal trends in the incidence.

Detection of Chlamydophila pneumoniae IgG in paired serum samples: comparison of serological techniques in pneumonia cases

Serological diagnosis of Chamydophila pneumoniae is usually undertaken by complement fixation test (CFT) or by microimmunofluorescence (MIF). A number of commercial methods for detecting C. pneumoniae-specific IgG have been developed. The aim of this study was to compare the performance characteristics of six methods for the diagnosis of pneumonia due to C. pneumoniae, including CFT (in house), MIF (Vircell, Spain), and four ELISAs (Medac, Germany; Savyon, Israel; Serion, Germany; and DRG, Germany). ELISA-Medac, ELISA-Savyon, ELISA-DRG and MIF use C. pneumoniae antigens while ELISA-Serion and CFT use Chlamydophila genus-specific antigen. Acute and convalescent samples from 85 pneumonia patients were studied. Using CFT, cases were initially classified as due to Chlamydophila (43 cases); to other agents (23 cases) (influenza A and B, Mycoplasma pneumoniae, respiratory syncytial virus, adenovirus and Legionella pneumophila); or as negative (19 cases). Cases were considered positive if they showed seroconversion, a significant rise in titer or high titer; and were finally classified as positive if they gave a positive result in at least three assays. Sensitivity values ranged from 87% to 97.8%; and specificity from 84.6% to 97.4%. In conclusion, the assays compared appear to be useful tools for the diagnosis of pneumonia due to Chlamydophila.

Simkania negevensis and newly diagnosed asthma: a case-control study in 1- to 6-year-old children

BACKGROUND

Simkania negevensis is an intracellular bacterium, sharing many characteristics with Chlamydophila and Chlamydia species. S. negevensis infection has been associated with bronchiolitis in infants and with pneumonia and exacerbations of COPD in adults.

OBJECTIVE

The aim of the present study was to evaluate, in a case-control setting, whether S. negevensis serology had any association with the onset of asthma in children.

METHODS

S. negevensis-specific IgM, IgA and IgG antibodies were measured by microimmunofluorescence in 104 children below school-age with newly diagnosed asthma, and in 122 control children.

RESULTS

S. negevensis-specific IgM was detected in two (2%) cases and in nine (8%) of the controls. IgG was detected in 12 (12%) cases and 12 (10%) of the controls. IgA antibodies were absent in all children. The age distribution of the 35 children with S. negevensis-specific antibodies was even, the positivity rate being 11% in the 12- to 23-month-old group and 20-23% in the children aged between 2 and 5 years.

CONCLUSION

Although S. negevensis appears to cause infections in the Finnish preschool-aged population, there was no association with asthma.

Chlamydia pneumoniae infection after lung transplantation

BACKGROUND

Chlamydia pneumoniae is established as a common agent of acute respiratory tract infection and has been implicated in the pathogenesis of asthma and chronic obstructive pulmonary disease. Airway disease is a prominent cause of morbidity and mortality after lung transplantation. We investigated the role of C pneumoniae as a pulmonary pathogen after lung transplantation.

METHODS

Eighty lung transplant recipients underwent 232 bronchoscopies with bronchoalveolar lavage with or without transbronchial lung biopsy during 1 year for surveillance of rejection and infection, or where clinically indicated.

RESULTS

C pneumoniae was detected using nested polymerase chain reaction in 9 of 36 (25%) recipients studied within 30 days of lung transplantation, 3 of whom remained positive on repeat lavage and died from airway disease in the first year post-operatively. By comparison, all 27 recipients with negative lavage survived >1 year. Lavage was positive for C pneumoniae in 18 of 71 (25%) recipients studied >30 days after lung transplantation, 5 of whom had pneumonia and 8 of whom had bronchiolitis obliterans syndrome. Eleven also had acute pulmonary allograft rejection.

CONCLUSIONS

Persistent infection with C pneumoniae (whether donor-derived, de novo or re-activated) appears deleterious to pulmonary allograft function and is associated with early mortality, rejection and bronchiolitis obliterans syndrome after lung transplantation. A trial of empiric antibiotic therapy for C pneumoniae may therefore be warranted in the attempt to prevent progressive inflammatory airway disease.

Chlamydia pneumoniae and lung cancer: epidemiologic evidence

Chlamydia pneumoniae is a common cause of acute respiratory infection and has been hypothesized to cause several chronic diseases, including lung cancer. The purpose of this article is to identify, describe, and critically examine the published studies on the association between C. pneumoniae infection and risk of lung cancer. In the six studies identified, previous C. pneumoniae infection was defined on the basis of serologic criteria, which varied between studies. All studies reported elevated relative risk estimates for the association of serologic evidence of infection and risk of lung cancer. The three studies in which past infection was defined based on testing of prediagnostic blood specimens tended to have weaker results (odds ratio range, 1.2-2.1) than those based on postdiagnostic blood specimens (odds ratio range, 1.4-9.9). Selection bias, measurement error, and inadequate control for confounding are concerns in some of these studies. Nevertheless, results were relatively consistent, supporting a causal association. Inflammation caused by chronic infection with C. pneumoniae may be involved in the carcinogenic process but this relationship will be difficult to further define through serologic data. To better understand the nature of this association, both experimental study designs, such as those based on animal models or randomized controlled antibiotic treatment trials in humans, and observational study designs (e.g., studies that involve detection of C. pneumoniae in pulmonary specimens obtained before cancer onset) could be explored and may shed additional light on this important association.

Microbiological profile of community-acquired pneumonia in adults over the last 20 years

OBJECTIVES

To assess any change in the microbiological profile of community-acquired pneumonia (CAP) in our region over the last 20 years.

METHODS

We compared hospital admissions aged between 15 and 74 (n = 61) in Norfolk (UK) for CAP over a 19-month period in 1982-3 (ST1) with all admissions aged over 16 (n = 99) over a 14-month period in 1999-2000 (ST2). Data were collected for ST1 as part of a prospective multicentred research study, in a period of high Mycoplasma pneumoniae activity. ST2 was a prospective study of clinical practice. Chlamydophila species were differentiated in ST2 using whole-cell immunofluorescence.

RESULTS

A microbiological diagnosis was made in 38 (62%) in ST1 compared with 48 (48%) in ST2. Streptococcus pneumoniae remained the most common pathogen (26% in ST1, 25% in ST2). The incidence of M. pneumoniae was 18% in ST1 and 4% in ST2. The proportion of viral pathogens identified was similar: nine (15%) in ST1 and 14 (14%) in ST2. No cases of Chlamydophila pneumoniae were diagnosed in ST2.

CONCLUSIONS

The microbiological profile of CAP in Norfolk (UK) has not changed over the last 20 years and C. pneumoniae is not a frequent pathogen.

Interlaboratory reliability of microimmunofluorescence test for measurement of Chlamydia pneumoniae-specific immunoglobulin A and G antibody titers

To evaluate the reliability of Chlamydia pneumoniae-specific immunoglobulin G (IgG) and IgA antibody titers as measured by the microimmunofluorescence (MIF) test, we compared results from 392 individuals using a standard MIF protocol at two academic laboratories. The kappas for dichotomous titers (>/=16 versus <16) were 0.39 for IgA and 0.53 for IgG. Measurement error likely attenuates C. pneumoniae-disease associations; the magnitude of attenuation can be estimated from results of studies such as this one.

Impact of serological methodology on assessment of the link between Chlamydia pneumoniae and vascular diseases

We assessed the impact of five serologic tests on the link between Chlamydia pneumoniae and abdominal aortic aneurysms (AAA). The results of the tests were inconsistent. Agreement among the five tests was generally poor. Detection of the link between C. pneumoniae and AAA depends on the serologic methodology chosen.

Evaluation and optimization of ELISA for detection of anti-Chlamydophila pneumoniae IgG and IgA in patients with coronary heart diseases

We have evaluated and optimized a commercial enzyme-linked immunosorbent assay (ELISA; SeroCP Savyon, Israel), using the commercial microimmunofluorescence test (MIF; Labsystems; Helsinki, Finland) as reference method. This was done for the detection of anti-Chlamydophila pneumoniae IgG and IgA antibodies in patients with coronary heart disease (CHD). After optimization, a good agreement between the ELISA and MIF tests [IgG (P(0.05)=0.0008 and r=0.93) and IgA (P(0.05)=0.00072 and r=0.72)] was found. These ELISA tests proved to be a useful semiquantitative method for seroprevalence studies in CHD patients, with remarkable advantages over MIF test in terms of objective measurement, thus reproducibility, performance and interpretation.

Comparison of quantitative and semiquantitative enzyme-linked immunosorbent assays for immunoglobulin G against Chlamydophila pneumoniae to a microimmunofluorescence test for use with patients with respiratory tract infections

We previously reported a high degree of variation in the sensitivities of serodiagnostic kits for the detection of Chlamydophila pneumoniae in sera from healthy donors. Since a low predictive value of a test can impair its diagnostic value, we have extended our studies to samples from patients with pneumonia. We focused on the most promising enzyme-linked immunosorbent assays (ELISAs) (SeroCP and SeroCP Quant; Savyon) identified in our previous study and included a new ELISA (sELISA; Medac). The agreement between all ELISAs for immunoglobulin G (IgG) and a reference microimmunofluorescence (MIF) test for IgG (SeroFIA; Savyon) was > or = 90% for a collective of 80 patients. The positive predictive values were all > or = 93%. The negative predictive values ranged from 68 to 83%. False-negative results were obtained only for samples that had low titers in the MIF test. The correlation of the IgG antibody titers determined by the MIF and SeroCP Quant tests was high (r(sp) = 0.9). Since the semiquantitative SeroCP and quantitative SeroCP Quant ELISAs achieved the highest sensitivities, they were evaluated further by using a second batch of sera from 50 patients with predominantly medium and low antibody titers in the MIF test and a control collection of sera from 80 children with negative MIF results. Again, the tests showed a high concordance with the MIF results (96%), and the antibody titers in the SeroCP Quant and MIF tests correlated well (r(sp) = 0.8). The specificities determined with the negative sera were > or = 99% for the SeroCP Quant test and 86% for the SeroCP test. These results show that ELISAs that are fast and objective deliver seroprevalence results, sensitivities, and specificities that are very similar to those of the MIF test.