Predictors of positive culture in NAAT-confirmed rectal N. gonorrhoeae infection among men who have sex with men

Background Gonorrhoea is a common sexually transmitted infection (STI) among men who have sex with men (MSM). Nucleic acid amplification tests (NAATs) are the recommended diagnostic method; however, the interpretation of positive results in asymptomatic individuals remains uncertain. The aim of this study was to identify factors associated with positive culture results in NAAT-confirmed rectal gonorrhoea. Methods This retrospective study included individuals receiving HIV care, pre-exposure prophylaxis or STI screening at the Infectious Diseases Unit of San Raffaele Hospital, Milan, Italy, between January 2021 and January 2025. Individuals with NAAT-confirmed rectal Neisseria gonorrhoeae who also underwent culture testing were included. Demographic and clinical data were collected. Group comparisons were performed between individuals with positive or negative cultures. Results Among 556 individuals with NAAT-confirmed rectal N. gonorrhoeae (552 MSM and 4 women who have sex with men), 200 (35.3%) had a positive culture. The median age was 35.7 years (IQR=30.7–41.9). Individuals with a positive culture were younger (34.9 vs 36.4 years; p=0.013) and more frequently symptomatic (56.5% vs 16.6%; p<0.001), particularly reporting anal burning, gastrointestinal symptoms, tenesmus and anal discharge (all p<0.001). Conclusions Gonococcal culture was positive in about one-third of NAAT-confirmed rectal infections. The presence of STI-related symptoms was associated with a positive culture. These findings corroborate the limited sensitivity of gonococcal culture and may help guide resistance surveillance strategies.