Chlamydia trachomatis is responsible for both trachoma and sexually transmitted infections causing substantial morbidity and economic cost globally. Despite this, our knowledge of its population and evolutionary genetics is limited. Here we present a detailed whole genome phylogeny from representative strains of both trachoma and lymphogranuloma venereum (LGV) biovars from temporally and geographically diverse sources. Our analysis demonstrates that predicting phylogenetic structure using the ompA gene, traditionally used to classify Chlamydia, is misleading because extensive recombination in this region masks true relationships. We show that in many instances ompA is a chimera that can be exchanged in part or whole, both within and between biovars. We also provide evidence for exchange of, and recombination within, the cryptic plasmid, another important diagnostic target. We have used our phylogenetic framework to show how genetic exchange has manifested itself in ocular, urogenital and LGV C. trachomatis strains, including the epidemic LGV serotype L2b.
Nested polymerase chain reaction (nPCR) demonstrated the presence of Chlamydia pneumoniaespecific DNA in peripheral blood mononuclear cells (PBMC). PBMC samples were obtained from 103 consecutive patients (62 male, 41 female) aged 22 -85 years (mean, 64) admitted for coronary angiography because of suspected coronary heart disease and from 52 blood donors (43 male, 9 female) aged 40 -64 years (mean, 49). Of the 101 evaluable patients, 60 (59%) were identified by nPCR assay as C. pneumoniae DNA carriers; C. pneumoniae -specific microimmunofluorescence (MIF) serology confirmed exposure to the bacterium in 57 (95%) of the 60 nPCR-positive patients. Among the 52 blood donors, the nPCR assay identified 24 (46%) C. pneumoniae DNA carriers, all of whom were positive by C. pneumoniae-specific serology. Thirty-two patients (32%) and 23 blood donors (44%) were MIF antibody -positive but repeatedly nPCR-negative; Bartonella henselae -or Bartonella quintana -specific antibodies were not detected among any of these subjects. In this study, C. pneumoniae DNA was common in PBMC of patients with coronary heart disease and in middle-aged blood donors.Chlamydia pneumoniae has been established as a common polymerase chain reaction (PCR) detection is a technically feasible approach that is becoming an important tool in the diagnoand important pathogen causing upper and lower respiratory tract infections in humans [1]. Also, several recent studies have sis of pulmonary tuberculosis and for monitoring the efficacy of antituberculosis therapy. suggested that C. pneumoniae may be implicated in atherosclerotic disease [2 -5], and treatment with antichlamydial antibiot-The advent of PCR technology has resulted in major advantages in the diagnosis of chlamydial infections, and we have ics may reduce the risk of recurrent ''cardiac events'' in patients with established atherosclerotic coronary heart disease recently shown that nested PCR (nPCR) is a sensitive and specific method for diagnosing patients with acute respiratory [6, 7].A properly performed serology may be of value in diagnos-C. pneumoniae infections [8]. The purpose of the present study was to investigate prospectively whether blood-based nPCR is ing an acute C. pneumoniae infection [8]. In the case of persistent C. pneumoniae infection, however, serology is less useful useful in identifying individuals carrying circulating C. pneumoniae DNA. [9]. Therefore, there is an obvious need for methods that could identify individuals persistently infected by C. pneumoniae.C. pneumoniae may be harbored in human monocytes [10], Methods and monocytes are therefore a potential reservoir and source Samples. Venous whole blood (10 mL) was collected in for diagnostic efforts. Mycobacterium tuberculosis is a case in EDTA-treated tubes from 103 consecutive patients (62 male, 41 point. In a study of patients with active M. tuberculosis infecfemale) aged 22-85 years (mean, 64) who were admitted to Umeå tion, Condos et al. [11] showed that peripheral blood-based University Hospital for coronary ...
Background: Chlamydia trachomatis is the most common cause of sexually transmitted infections globally and the leading cause of preventable blindness in the developing world. There are two biovariants of C. trachomatis: 'trachoma', causing ocular and genital tract infections, and the invasive 'lymphogranuloma venereum' strains. Recently, a new variant of the genital tract C. trachomatis emerged in Sweden. This variant escaped routine diagnostic tests because it carries a plasmid with a deletion. Failure to detect this strain has meant it has spread rapidly across the country provoking a worldwide alert. In addition to being a key diagnostic target, the plasmid has been linked to chlamydial virulence. Analysis of chlamydial plasmids and their cognate chromosomes was undertaken to provide insights into the evolutionary relationship between chromosome and plasmid. This is essential knowledge if the plasmid is to be continued to be relied on as a key diagnostic marker, and for an understanding of the evolution of Chlamydia trachomatis.
Genotyping of Chlamydia trachomatis is limited by the low sequence variation in the genome, and no adequate method is available for analysis of the spread of chlamydial infections in the community. We have developed a multilocus sequence typing (MLST) system based on five target regions and compared it with analysis of ompA, the single gene most extensively used for genotyping. Sequence determination of 16 reference strains, comprising all major serotypes, serotypes A to L3, showed that the number of genetic variants in the five separate target regions ranged from 8 to 16. The genetic variation in 47 clinical C. trachomatis isolates of representative serotypes (14 serotype D, 12 serotype E, 11 serotype G, and 10 serotype K strains) was analyzed; and the MLST system detected 32 variants, whereas 12 variants were detected by using ompA analysis. Specimens of the predominant serotype, serotype E, were differentiated into seven genotypes by MLST but into only two by ompA analysis. The MLST system was applied to C. trachomatis specimens from a population of men who have sex with men and was able to differentiate 10 specimens of one predominant ompA genotype G variant into four distinct MLST variants. To conclude, our MLST system can be used to discriminate C. trachomatis strains and can be applied to high-resolution molecular epidemiology.Chlamydia trachomatis can be subdivided by serological typing, based on the major outer membrane protein, into at least 15 serotypes. Serotypes A to C are associated with ocular trachoma, serotypes D to K preferably colonize the urogenital tract, and serotypes L1 to L3 cause lymphogranuloma venereum.Serotyping of Chlamydia is laborious since it requires multiple passages in cell culture and the use of a large panel of monoclonal antibodies. Genotyping methods are more commonly used, and the major outer membrane protein gene, ompA, provides the best discriminatory capacity of the genes tested. Restriction fragment length polymorphism analysis of ompA is rapid, and its results show a high level of agreement with the results serotyping (9), while DNA sequencing of ompA has a higher resolution and can discriminate strains in clinically high-risk populations (2, 14). However, when it is applied to nonselected populations, the limited resolution of ompA sequencing restricts the amount of epidemiological information that can be obtained (6). This is especially true, given that the single serotype E comprises almost half of all urogenital chlamydial infections, and within this serotype, one genotypic variant appears to predominate (3, 4, 6). There is therefore an obvious need to develop better methods for evaluation of the molecular epidemiology of chlamydial infections. Furthermore, it has recently been shown that mutant strains evade systems commonly used for the detection of C. trachomatis (11). At present little is known about the spread of such changed chlamydial strains, but they are known to be prevalent in several regions of Sweden and are probably prevalent elsewhere. In this conte...
BackgroundDiagnosis of Mycoplasma pneumoniae (MP) infection is traditionally based on serology, which may require more than two weeks for diagnostic antibodies to develop. PCR-based methods offer earlier diagnosis. During a community outbreak of MP infection, we compared semi-nested and real-time PCR of oropharyngeal swabs with serology for diagnosis of MP infection at different time points after disease onset. PCR-positive individuals were followed longitudinally to assess the persistence of MP DNA in throat secretions. We also studied carriage of MP among household contacts and school children.ResultsMP infection was diagnosed in 48 of 164 patients with respiratory tract infection. Forty-five (29%) had detectable MP DNA in oropharynx. A significant increase in MP IgG IgG titre or MP IgM antibodies was detected in 44/154 (27%) subjects. Two MP PCR-positive patients lacked antibody responses. Sera were missing from another two patients. The agreement between serology and PCR was good, κ = 0.90.During the first three weeks after disease onset the performance of PCR was excellent and all patients but one were detected. In contrast, only 21% of the patients with confirmed MP infection were positive by serum 1 during the first symptomatic week (56% during the second and 100% during the third week). Only 1/237 (0.4%) school children was positive by PCR. This child had respiratory symptoms. Eighteen of 22 (75%) symptomatic household contacts were MP PCR positive.Persistence of MP DNA in the throat was common. Median time for carriage of MP DNA was 7 weeks after disease onset (range 2 days – 7 months). Adequate antibiotic treatment did not shorten the period of persistence. Bacterial load, measured by quantitative real-time PCR declined gradually, and all followed patients eventually became PCR-negative.ConclusionPCR is superior to serology for diagnosis of MP infection during the early phases of infection. Persistent, sometimes long-term, carriage of MP DNA in the throat is common following acute infection, and is not affected by antibiotic therapy. Asymptomatic carriage of MP even during an outbreak is uncommon.
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