Background Diagnosisof urogenital Chlamydia infection can be a challenging task in some cases due to difficulties in detection of the pathogen at the anatomical sites of humans. The goal of this study was to compare the efficiency of detection of C. trachomatis in samples obtained from different anatomical sites of patients.

Methods Clinical specimens from both genital (urethra, cervix) and extragenital sites (pharynx, conjunctive) were collected from patients with either urogenital (Group 1, n = 7) or extragenital Chlamydia infection (Group 2, n = 2). Presence of Chlamydia in these samples was determined by PCR with primers to the C. trachomatis cryptic plasmid genes, as well as by commercial direct fluorescent test (DFT) and dot-ELISA.

Results Among Group 1 patients, 85.7% urethral & cervical, 75% conjunctive and 50% pharyngeal samples were positive in PCR. Notably, DNA isolated from specimens of one individual showed negative result to Chlamydia at anatomical site, yet displayed a positive reaction in samples taken from both extragenital sites. Moreover, 100% of samples obtained from all different sites reacted positively in dot-ELISA for each patient. Six out of seven patients were positive for Chlamydia by DFT assay in samples acquired from the genital site (urethral & cervical scrapes). Group 2 patients gave 100% positive response in PCR tests with DNA from genital and at least from one of the extragenital sites.

Conclusions We found that in patients with urogenital Chlamydia infection positive reactions could be detected with high frequency at extragenital sites by both PCR and antibody-based assays. Thus, testing clinical specimens obtained from extragenital sites can facilitate detection of Chlamydia, resulting in a significant increase of the efficiency of laboratory diagnosis of Chlamydia for Public Health.

This work was supported by the Project #3846 NIH/BTEP/ISTC.