Assessment of rectalChlamydia trachomatisviable load in women by viability-PCR

Abstract

ObjectivesIn recent years, studies have demonstrated frequent rectal Chlamydia trachomatis (CT) detection in women, irrespective of reported anal sex or rectal symptoms. However, the clinical relevance and public health implication of rectal CT detection in women remain under debate. Therefore, evaluating CT viability may provide more insight into the relevance of standard routine nucleic acid amplification test (NAAT)–positive results.MethodsIn this cross-sectional explorative study, a convenience sample of female patients at our STI clinic aged 18 years or older, diagnosed with vaginal and/or rectal CT, were invited to participate. On return for treatment, rectal CT-diagnosed women were instructed to self-collect rectal swab samples before being treated. Standard COBAS 4800 CT/NG routine NAAT testing was applied for CT diagnosis. Rectal viable CT load was evaluated by using viability-PCR (V-PCR).Results53 women with rectal CT were included in this study; 86.8% (46/53) had a quantifiable rectal total CT load. Of women with quantifiable samples, 52.2% (24/46) had viable CT detected from rectal swabs by V-PCR, with a mean rectal viable CT load of 3.31 log10 CT/mL (range 1.16–6.22). No statistically significant difference (p=0.73) was observed in the mean rectal viable CT load of women with an indication for rectal testing (n=9) and without (n=15), 3.20 log10 CT/mL (range 2.06–4.36) and 3.38 log10 CT/mL (range 1.16–6.22), respectively. CT culture yielded positive test results from rectal swabs in 22.6% (12/53) of rectal CT NAAT-diagnosed women. Of women with viable rectal CT by V-PCR (n=24), 50% (12/24) were positive by CT culture.ConclusionsOverall, the detection of high rectal viable CT loads in this study indicates that rectal CT in some women might represent a currently ongoing infection rather than just the presence of remnant DNA from dead bacteria or only contamination from an active vaginal CT infection.

Chlamydia and gonorrhea epidemiology

“…In a study conducted by our researchers, a sample (n=105) of concurrently infected STI clinic women showed that in the majority of cases (in 79% and 56% of women reporting anorectal intercourse and no anorectal intercourse, respectively), the anorectal CT load was in the same range as the urogenital CT load, suggesting similar clinical relevance. 33 Moreover, in the current study, we confirmed this finding and also showed that the anorectal CT load in men equals that of women. We saw as many low as high anorectal loads in both men and women as suggested in an earlier smaller study based on CT qPCR.…”

“…For example, a study did not observe a difference in anorectal NG between MSM who had receptive penile-anal sex (8.8%) and MSM who did not (6.6%). 33 This could indicate that other factors, such as receptive fingering, may also play a role the transmission of anorectal NG. 11 Oropharyngeal NG is mainly transmitted via condomless oral-genital contact.…”

Viability PCR shows that non-ocular surfaces could contribute to transmission of Chlamydia trachomatis infection in trachoma

“…A vial of PMA (0.5 mg) was reconstituted in 782μl 20% DMSO to obtain a stock concentration of 1250 μM and subsequently stored in the dark at 4˚C. Treatment conditions were optimized, and PMA concentrations were in line with previous studies [17,18,26,27]. PMA stock solution was added to each sample to a final concentration of 50 μM, with resulting mixtures then incubated for 15 minutes in the dark on ice.…”

“…Traditionally, cell culture is the gold standard for the assessment of Ct viability, but the sensitivity of culture compared to RNA-or DNA-based nucleic acid amplification tests is low, varying in head-to-head comparisons from 20-83% [11][12][13][14][15][16]. One promising method to overcome this problem with Ct diagnostics is viability PCR which uses propidium monoazide (PMA) as a sample pre-treatment before performing PCR, as recently described by Janssen et al [17,18]. PMA irreversibly crosslinks with DNA from membrane-impaired (non-viable) bacteria, and by occupying potential primer binding sites, makes it unavailable for amplification and detection by PCR.…”

Spontaneous clearance ofChlamydia trachomatisaccounting for bacterial viability in vaginally or rectally infected women (FemCure)

“…Hence, we may propose another definition of clearance to the detection of viable CT only (ie, to consider clearance having occurred when there is no more viable CT and ignore remnant bacterial DNA). Recently, we validated a PCR method for assessment of CT viability (V-PCR) in clinical swab samples 15 16. This method combines the high sensitivity and specificity of PCR with the ability to exclude detection of nucleic acid remnants from non-viable CT.…”