Gonococcal Antimicrobial Susceptibility Similar in MSW and Women; Higher in MSM

PHILADELPHIA, PA—Surveillance based on antimicrobial susceptibility of urogenital Neisseria gonorrhoeae in men who have sex with women (MSW) may represent susceptibility of urogenital N. gonorrhoeae in women, for whom data are few, a study reported at IDWeek 2014.

Gonorrhea is the second most notifiable disease in the U.S., with 333,004 cases reported to the Centers for Disease Control and Prevention (CDC) in 2013 alone. Effective treatment options remain limited; in fact, there is only one recommended first-line regimen, dual treatment with intramuscular ceftriaxone 250mg with oral azithromycin 1g.

In the U.S., surveillance of gonococcal antimicrobial susceptibility is exclusive to men with symptomatic urethral infection, who yield the highest gonococcal culture. Susceptibility of female urogenital isolates, and whether susceptibility among MSW is representative of women, remain largely unknown.

To address this, Sarah Kidd, MD, of the CDC’s National Center for HIV/AIDS, Hepatitis, STD, and TB Prevention in the Division of STD Prevention, Atlanta, GA, and colleagues compared susceptibility of urogenital gonococcal isolates from women, MSW, and men who have sex with men (MSM) by secondary analysis of data from a recent gonorrhea treatment trial.

From 2010–2012, pretreatment isolates were collected from trial participants in 5 U.S. cities: Birmingham, AL; Pittsburgh, PA; Baltimore, MD; San Francisco, CA; and Los Angeles, CA. A total of 56 women, 252 MSW, and 170 MSM were included in the analysis. Minimum inhibitory concentrations (MICs) were determined by agar dilution, and geometric mean MICs were adjusted for geographic location using general linear models.

Among women, the majority of the urogenital isolates were from Birmingham (66.1%) and Pittsburgh (19.6%). Among MSW, 41.3% of the isolates were from Birmingham, 31.0% from San Francisco, and 24.2% from Pittsburgh. For MSM, 83.5% of the isolates were from San Francisco.

The adjusted geometric mean ceftriaxone MIC was significantly higher among MSM (0.010µg/mL, 95% CI 0.008–0.012µg/mL) than MSW (0.006µg/mL, 95% CI 0.005–0.007µg/mL), but similar among MSW and women (0.007µg/mL, 95% CI 0.005–0.009µg/mL).

A similar pattern was reported for cefixime (women: 0.016µg/mL, 95% CI 0.011–0.024µg/mL; MSW: 0.017 µg/mL, 95% CI 0.016–0.019 µg/mL; MSM: 0.023µg/mL, 95% CI 0.020–0.028µg/mL) and azithromycin (women: 0.157µg/mL, 95% CI 0.108–0.228µg/mL; MSW: 0.174µg/mL, 95% CI 0.155–0.195µg/mL; MSM: 0.280µg/mL, 95% CI 0.241–0.325µg/mL).

Ceftriaxone, cefixime, and azithromycin MICs were significantly higher among MSM than MSW, as seen previously, but MICs were similar among MSW and women, a trend previously described in the Gonococcal Isolate Surveillance Project, a sentinel surveillance system located in 25–30 U.S. cities, and in Europe.

These findings “suggest susceptibility among MSW urethral isolates adequately represents susceptibility among female urogenital isolates,” Dr. Kidd said, as well as support the current CDC treatment recommendations.