Introduction: Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG) and Mycoplasma genitalium (MG) represent the most common agents of bacterial sexually transmitted infections (STIs), worldwide. In women, uro-genital infections caused by these microorganisms are often asymptomatic and, left untreated, can lead to several sequelae. Nucleic acid amplification techniques (NAATs) have become the reference methods for the diagnosis, thanks to the suitability for different specimens and the outstanding sensitivity and specificity. The aim of this study was to assess the performance of Aptima Assays for CT, NG and MG detection in a group of selected women, by a head-to-head comparison with other NAATs. Moreover, an evaluation about the suitability for the Aptima assays with one of the most used swab collection device (E-Swab; Copan) was carried out.
Methods Routinely, all the women attending the STI Outpatients Clinic of Sant’Orsola-Malpighi Hospital of Bologna (Italy) complaining of genital STI-related symptoms or reporting unsafe intercourse, are managed as follows. After a clinical visit, a sample of first-void urines and a vaginal swab collected in E-swab, are obtained for CT, NG and MG detection. A duplex real-time PCR (Versant CT/GC DNA 1.0 assay; Siemens) is used for CT and NG detection, while, MG presence is investigated by a home-made PCR, starting from the remaining eluate of Versant PCR plate. From January 2016, a total of 100 patients were selected and their samples were also tested with Aptima assays. Previously frozen samples were thawed and transferred to the suitable collection devices for Aptima assays: in particular, 2 ml of urines and 100 µl of vaginal E-swab were used. All the specimens were processed by Aptima Combo2® for CT and NG detection and by the Aptima® Mycoplasma genitalium assay for MG infection diagnosis. These assays were run on Panther system (Hologic). A comparison between the different molecular methods, stratified by type of sample and microorganism, was conducted.
Results In the group of 100 women selected, 25 patients were positive for CT, 4 for NG and 6 for MG. One case of CT-NG and two cases of CT-MG co-infections were found. Interestingly, more than 50% of CT-positive women were completely asymptomatic. By the routine tests, all positive cases were simultaneously found both on the urine sample and on the vaginal swab, except for 3 CT, 1 NG and 1 MG infections, detected only on the vaginal swab. A complete concordance with Aptima assays, both for the type of sample and microorganism was found, with only one discordant result (a CT case detected by Versant on urines and vaginal swab, found by Aptima only on urines). Any interference due to the different liquid components of E-Swab was excluded.
Conclusion Given the outstanding performance, Aptima assays can represent an excellent choice for CT, NG and MG molecular detection. Moreover, it is noteworthy that Aptima assays allow testing of specimens collected by E-Swab, enabling the possibility to use the same sample for both NG molecular detection and culture.
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