Infection with a plasmid-free variant Chlamydia related to Chlamydia trachomatis identified by using multiple assays for nucleic acid detection

Abstract

Clinical samples in transport media from 40 patients exhibiting pathologies potentially caused by Chlamydia trachomatis infection were analyzed for chlamydial nucleic acid, and the results were compared with those of culture. Chlamydial culture was performed by a shell vial centrifugation method with HeLa 229 host cells. Polymerase chain reaction (PCR) assays were used to detect either regions on a 7.5-kb plasmid characteristic of C. trachomatis (plasmid-PCR) or a segment of the 16S rRNA genes (rRNA-PCR). All PCR results were confirmed by hybridization with probes for the specific amplified products in either a Southern or a dot blot format. An RNase protection (RNP) assay was used to detect genus-specific chlamydial 16S rRNA directly from the clinical samples. The PCR assays detected C. trachomatis but not other bacteria, including Chlamydia spp. C. trachomatis was isolated from six samples which were positive by the rDNA-PCR and plasmid-PCR assays. Five of the culture-positive specimens were positive by the RNP assay. Twenty-two samples were negative by all criteria. Surprisingly, nine samples were positive by rRNA-PCR and RNP assays only. Nucleic acid sequencing of the rRNA-PCR-amplified products indicated a close relationship between the variants and C. trachomatis. The data may indicate an unrecognized process in C. trachomatis infection or that these patients were infected by a variant strain of C. trachomatis which lacks the C. trachomatis-specific plasmid.

Sensitivities of PCR, MicroTrak, ChlamydiaEIA, IDEIA, and PACE 2 for purified Chlamydia trachomatis elementary bodies in urine, peripheral blood, peripheral blood leukocytes, and synovial fluid

“…The PCR used in this study was found to be the most sensitive method for all compartments analyzed, with detection limits comparable to those reported for other C. trachomatisspecific PCRs (1,18,23,26).…”

Unraveling the basic biology and clinical significance of the chlamydial plasmid

“…Within C. trachomatis clinical isolates, the plasmid is virtually ubiquitous. There are occasional studies showing plasmid-negative clinical strains, but little is known about the epidemiology and significance of these relatively rare isolates (Peterson et al, 1990; An et al, 1992; Farencena et al, 1997). Chlamydial plasmids are nonconjugative and nonintegrative.…”

Molecular genetic methods for diagnosis and characterisation of Chlamydia trachomatis and Neisseria gonorrhoeae: impact on epidemiological surveillance and interventions

“…Using the plasmid as target DNA could theoretically increase the sensitivity compared to using a single chromosomal gene such as the omp1 gene (19). However, some studies suggest that plasmid‐free variants of C. trachomatis may on rare occasions be present in clinical samples (20), and these will not be detected if the plasmid is used as target DNA. NAATs available for detection of the cryptic plasmid in C. trachomatis in clinical specimens are the COBAS Amplicor ® Chlamydia trachomatis Test (Roche Diagnostic Systems), which is a PCR, and the Becton Dickinson BDProbeTec TM ET (Becton Dickinson) test, which uses strand displacement amplification (SDA).…”