Objectives To investigate the performance of the Bio-Rad Dx CT/NG/MG Assay with an internal control for the detection of Chlamydia trachomatis (CT) and Mycoplasma genitalium (MG) in urogenital samples in comparison with the Roche Cobas TaqMan CT test and an in-house TaqMan PCR test for MG. For Neisseria gonorrhoeae (NG), only positive PCR results were controlled by culture.

Methods In this prospective study, urogenital samples were obtained from symptomatic and asymptomatic patients attending the STI center of Bordeaux, France, from January to April 2010. For symptomatic women and men, two endocervical swabs and two urethral swabs were collected, respectively. All patients and women collected first-catch urines and two vaginal swabs, respectively. Two swabs per site were used, a flocked swab in the universal transport medium and the Bio-Rad flocked swab in its transport medium. For the Bio-Rad CT/NG/MG assay, the DNA was manually extracted and amplified according to the manufacturer's instructions. For the comparator PCR tests, DNA was extracted using the MagNa Pure LC instrument (Roche Diagnostics) and amplified with the Cobas TaqMan CT 48 assay (Roche Diagnostics) and with a MgPa-targeted PCR assay on an ABI Prism 7000 (Applied Biosystems) for MG. The patient was considered as infected if at least two of the 4 or 6 PCR tests performed according to the gender and characteristics of patients, were positive. For asymptomatic men, in case of discrepancy, the urine sample was retested by both methods and the patient was considered infected if at least two of the four PCR results were positive for the considered microorganism.

Results A total of 658 clinical specimens (259 male and 180 female urines, 191 vaginal, 21 cervix and seven urethral swabs) from 453 patients were analysed. The prevalence of CT and MG infections was 7.7% (20/260) and 1.9% (5/260) in men and 10.3% (20/193) and 2% (4/193) in women, respectively. The Bio-Rad Dx CT/NG/MG test sensitivity was 100% for CT and MG in men and women. In male urines, the specificity was 99.6% for CT and 100% for MG. In women, the specificity was 99.5% for swabs and 100% for urines for CT and MG. All 7 NG-PCR positive samples were positive by culture. Patients were co-infected in 5/56 (9%) with CT/MG in three cases and CT/NG in two cases.

Conclusion The Bio-Rad Dx CT/NG/MG Assay was found to be very effective for the simultaneous detection of CT, MG, and NG infections in urogenital specimens.