Comparison of a ligase chain reaction-based assay and cell culture for detection of pharyngeal carriage of Chlamydia trachomatis

What would be missed if we didn't screen men who have sex with men for oral chlamydia trachomatis? A cross-sectional study

Background This study aimed to describe oropharyngeal chlamydia (OCT) in gay and bisexually active men (GBM) attending a large urban sexual health clinic in Sydney and determine what proportion of cases would be missed if screening was not routine.

METHODS

Retrospective data were extracted for all GBM with a positive OCT result between 1 October 2012 and 31 April 2014. The control group consisted of patients who had a negative OCT result on their first visit during the study period, and each patient was only counted once.

RESULTS

A total of 74 of 2920 GBM (0.03, 95% CI: 0.02-0.03) were diagnosed with OCT. The 2920 GBM had a total of 11226 OCT tests performed, demonstrating OCT test positivity of 0.006 (95% CI: 0.005-0.008). A total of 62 sexually transmissible infections (STIs) were diagnosed at other sites: 34 rectal chlamydia (CT), 12 throat gonorrohea (GC), 7 urine CT, 7 rectal GC, 1 infectious syphilis and 1 non-gonoccal urethritis (NGU) case. Of the 74 OCT cases, 56 (0.76, 95% CI: 0.64-0.85) were treated with Azithromycin; 51 (69%) as part of standard treatment for their STI co-infection (34 rectal CT, 12 throat GC, 7 urine CT, 7 rectal GC, 1 NGU case) and a further five (7%) were treated as contacts. The remaining 18 people (0.24, 95% CI: 0.15-0.36) would not have been treated unless they were tested specifically for OCT.

CONCLUSION

Overall, two-thirds of the OCT cases received appropriate treatment and only a small number of cases would have been missed had routine screening not been performed. With an extremely low overall test positivity of 0.6%, screening for OCT at our service adds little to population level health control.

Usefulness of oral wash specimens for detecting Chlamydia trachomatis from high-risk groups in Japan

Orogenital sex is recognized as a route for the transmission of Chlamydia trachomatis (CT) which thus causes male chlamydial urethritis. Patients with a pharyngeal CT infection have no gross lesions, but CT was tested by pharyngeal swabs. In this study, the usefulness of oral wash specimens for detecting CT was compared to that of swab specimens. In addition, oral wash specimens were also used to screen for CT pharyngeal infection. Eighteen female commercial sex workers in whom CT was detected from pharyngeal swabs were re-examined using both methods. The positive rate for CT was 44% by swabs and 61% by oral wash specimens. Forty-eight male students with CT-positive urine were also screened for pharyngeal CT infection. The positive rates were 6% by swabs and 10% by oral wash specimens. Our findings therefore indicate that oral wash specimens more effectively detected pharyngeal CT infection than pharyngeal swabs.

Diagnóstico de la infección por Chlamydia trachomatis en un centro de diagnóstico y prevención de infecciones de transmisión sexual: evaluación de los exudados cervicales, uretrales y rectales mediante técnica de PCR

INTRODUCTION

The aim of this study is to analyze the clinical and epidemiological characteristics of Chlamydia trachomatis infection in patients attended in a clinic for sexually transmitted disease in Seville (Spain). Microbiological diagnosis was performed in various types of samples.

MATERIAL AND METHODS

The study included 3854 patients (50.8% women and 49.2% men, mean age 30.1 years) seen from 2002 to 2004. Among the total, 50% belonged to groups engaging in high risk sexual practices: female commercial sex workers (CSWs) (47%), men who maintain sexual relationships with other men (MSM) (45%), users of prostitution (4%), promiscuous heterosexual men (4%), those with a risk partner (2.7%) and injection drug users (IDU) (2.2%). We analyzed a total of 5978 samples (2384 cervical exudates, 2645 urethral exudates and 949 rectal exudates), for the detection of C. trachomatis by PCR technique with the COBAS Amplicor CT System.

RESULTS

Prevalence of C. trachomatis infection was 6% (4.3% in women and 7.8% in men). Among the total in women, 51.2% of positive samples were from women with high-risk sex factors and 73.8% of the women were asymptomatic. In men, the proportions were 70.5% and 36.9%, respectively. Cervical, urethral and rectal exudates yielded positive results in 4%, 4.9% and 4.3%, respectively.

CONCLUSIONS

Systematic sampling for C. trachomatis detection is necessary in symptomatic and asymptomatic patients practicing high-risk sex; periodic follow-up studies are also needed for early detection of sexually transmitted infection. Rectal sample collection is important for detecting this infection in MSM and in patients whose sexual habits make it advisable.

Enhanced enzyme immunoassay with negative-gray-zone testing compared to a single nucleic Acid amplification technique for community-based chlamydial screening of men

We evaluated a low-cost diagnostic strategy for detecting Chlamydia trachomatis in a low-prevalence population. We used an amplified enzyme immunoassay (EIA) with a reduced-cutoff "negative gray zone" to identify reactive specimens for confirmation by a nucleic acid amplification test. As part of the Chlamydia Screening Studies project, men provided a first-pass urine specimen, which they returned by post for testing. We tested 1,003 specimens by IDEIA PCE EIA (Dako) and Cobas PCR (Roche). There were 32 (3.2%) true positive specimens according to a combined standard using an algorithm requiring concordant results from at least two independent tests. All of these were positive by Cobas PCR and 24 were confirmed to be positive by PCE EIA, including 2 that gave results in the negative gray zone. There were 971 true negative specimens, 2 of which were positive by Cobas PCR and 19 of which were initially inhibitory for PCR. The relative sensitivity, specificity, positive predictive value, and negative predictive value of PCE EIA with PCR confirmation were 75.0% (95% confidence interval [CI], 56.6 to 88.5%), 100% (95% CI, 99.7 to 100%), 100% (95% CI, 88.3 to 100%), and 99.2% (95% CI, 98.4 to 99.6%), respectively. The corresponding values for Cobas PCR were 100% (95% CI, 89.1 to 100%), 99.8% (95% CI, 99.3 to 100%), 94.1% (95% CI, 76.9 to 98.2%), and 100% (95% CI, 99.6 to 100%), respectively, with 1.9% (19/1003) of the samples being initially indeterminate. When the prevalence of C. trachomatis is low, the use of an amplified EIA on urine specimens, with confirmation of results in the negative gray zone by use of a nucleic acid amplification technique, is not suitable for screening asymptomatic men. In addition, positive nucleic acid amplification test results should be confirmed and an inhibition control should be used.

Prevalence of rectal, urethral, and pharyngeal chlamydia and gonorrhea detected in 2 clinical settings among men who have sex with men: San Francisco, California, 2003

BACKGROUND

The Centers for Disease Control and Prevention developed screening and diagnostic testing guidelines for chlamydia and gonorrhea at urethral, rectal, and pharyngeal sites for men who have sex with men (MSM). However, in most clinical settings, rectal chlamydial testing is not performed for MSM, and primarily sexually transmitted disease (STD) clinics alone perform routine rectal and pharyngeal gonorrhea screening for asymptomatic men.

METHODS

We evaluated the prevalence of rectal, urethral, and pharyngeal chlamydial and gonococcal infections among MSM seen at the municipal STD clinic and the gay men's community health center. We also determined the proportion of asymptomatic rectal infections, described the patterns of single and multiple anatomic sites of infection, and evaluated the proportion of chlamydial infections that would be missed and not treated if MSM were not routinely tested for chlamydia. We tested specimens using previously validated nucleic acid amplification tests (NAATs).

RESULTS

The prevalence of infection varied by anatomic site (chlamydia: rectal, 7.9%; urethral, 5.2%; and pharyngeal, 1.4%; for gonorrhea, rectal, 6.9%; urethral, 6.0%; and pharyngeal, 9.2%). Approximately 85% of rectal infections were asymptomatic supporting the need for routine screening. Because 53% of chlamydial infections and 64% of gonococcal infections were at nonurethral sites, these infections would be missed and not treated if only urethral screening was performed. In addition, >70% of chlamydial infections would be missed and not treated if MSM were tested only for gonorrhea.

CONCLUSIONS

Because these infections enhance both HIV transmission and susceptibility, clinical settings serving MSM should evaluate the prevalence of chlamydial and gonococcal infections by anatomic site using validated NAATs.

Validation of roche COBAS Amplicor assay for detection of Chlamydia trachomatis in rectal and pharyngeal specimens by an omp1 PCR assay

Screening guidelines for men who have sex with men (MSM) recommend testing of extragenital sites (pharyngeal and rectal) for gonorrhoea and chlamydia. Testing of specimens from these sites is not validated by most commercial nucleic amplification tests, such as the COBAS Amplicor assay. To investigate the utility of the COBAS Amplicor assay for detection of Chlamydia trachomatis in extragenital specimens, this study developed and evaluated confirmatory tests using the omp1 gene as an alternative target for amplification by PCR. Of anal and throat swabs collected from men in male-only saunas, 52 swabs that tested C. trachomatis positive by COBAS Amplicor and 30 swabs that tested as negative were included for confirmatory omp1 PCR testing. A total of 49 (94%) COBAS Amplicor-positive samples were confirmed by the omp1 PCR. A substantial proportion of specimens were confirmed by using a nested omp1 PCR (27%). Not confirmed by any omp1 PCR were three anal swabs (6%). It is most probable that these samples contained lower bacterial levels that were near or below the detection level of the omp1 PCR assays. The findings of this study support the confident reporting of C. trachomatis detected by COBAS Amplicor in extragenital specimens and support the utility of this assay as a screening test for MSM.