The Use of Real-Time PCR to Screen Nesseria Gonorrhoeae Isolates for PenA Alterations — San Francisco, 2009

Background: First-line treatment regimens for Neisseria gonorrhoeae include only the third-generation cephalosporins. However, resistance to oral cephalosporins has been reported globally and is associated with a “mosaic” penA gene. We previously reported isolates in San Francisco with a similar penA gene, but have identified no known clinical treatment failures.

Objectives: To identify patients potentially at risk for treatment failure, we sought to test clinical specimens for penA alterations.

Methods: Using a real-time PCR melting curve assay for mosaic penA, we tested gonorrhea-positive clinical specimens collected at the San Francisco municipal STD clinic for culture or transcription mediated amplification (TMA). To facilitate assessment of treatment outcome and because parameters for using TMA as a test of cure are unknown, only specimens from persons with symptoms were tested.

Results: During April-August 2009, 332 specimens tested positive for gonorrhea; 154 (46.2%) were from patients with symptoms. Of those, 127 (82.5%; 53 culture and 74 TMA specimens) were tested by PCR for mosaic penA. Of those127 specimens, 18 (14.2%) were negative for gonorrhea by PCR (all were gonorrhea-positive TMA specimens). Of the remaining 109, four (3.7%) tested positive for a mosaic penA allele associated with decreased cephalosporin susceptibility. Among these 4 patients, 3 were men; 2 were men who had sex with men. All were African American. None reported international travel in the prior 1 month; none were HIV infected. All had received cefpodoxime 400mg + azithromycin 1gm on symptomatic presentation to the clinic. Among the 3 patients contacted for follow up information, no treatment failures were identified.

Conclusions: Real-time PCR can be used to identify patients at potential risk for oral cephalosporin treatment failure.

Implications for Programs, Policy, and/or Research: Use of molecular methods to identify possible cephalosporin resistance might be a useful and timely adjunct to culture-based susceptibility surveillance.