Background Despite nucleic acid amplification tests (NAAT) are widely used to detect Neisseria gonorrhoeae infections, so far no commercial kit has been cleared for testing rectal or pharyngeal swab samples, even if anal and/or oral sex practises are common.
In this study, a comparison between Real Time PCR Versant CT/GC DNA 1.0 (Siemens) and N. gonorrhoeae culture performances has been conducted, testing rectal or pharyngeal secretions collected by E-swabs (Copan).
Methods Study group. A prospective study was performed with 171 subjects (130 males and 41 females) attending the STD Outpatients Clinic of St. Orsola Hospital, Bologna. All the patients were enrolled because having unsafe receptive anal and/or pharyngeal sex intercourses.
NAAT methods. All the specimens were tested by Versant CT/GC DNA 1.0. As a confirmation, all the specimens scored positive for N. gonorrhoeae were retested, using the same extraction, by a “home-made” PCR assay, targeting cppB gene.
N. gonorrhoeae culture. Bacteria were isolated in Thayer-Martin medium and identified by API NH assay (bioMérieux). Antimicrobial susceptibility was assessed by Kirby-Bauer Test.
Results A total of 227 samples were obtained. In particular, 56 patients provided both the specimens, 89 patients provided only pharyngeal swabs, whereas only rectal specimens were collected from the remaining 26 patients.
Versant CT/GC DNA 1.0 gave positive results for N. gonorrhoeae in 13 pharyngeal in 7 rectal samples, all from MSM. All the Versant reactive results were confirmed by “home-made” PCR. Prevalence of rectal infection was 8.5% (7 positive out of 82 patients), whereas prevalence of pharyngeal infection was 9.0% (13/145). Culture was far less sensitive than NAAT, since only 4 samples were identified. All of them were resistant to quinolones, but susceptible to cephalosporins (cefixime and ceftriaxone).
Conclusions Pharyngeal and/or rectal screening for gonorrhoea should be considered essential in consultations for MSM in STD clinics.
- nucleic acid amplification tests
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