Culture yield of Neisseria gonorrhoeae: culture yield varies by anatomical site and time to culture collection

BACKGROUND: Neisseria gonorrhoeae (NG) is one of the World Health Organization's high-priority bacterial pathogens due to the emergence of multidrug-resistant strains. The culture of NG remains important for providing antimicrobial resistance surveillance data. OBJECTIVE: To determine the NG culture yield following a positive NG nucleic acid amplification test (NAAT) within 30 days, stratified by culture specimen collection sites, the time interval between NAAT and culture, and gender. METHODS: A retrospective data analysis of positive NG NAAT specimens of individuals attending the Melbourne Sexual Health Centre between April 2015 and March 2023. We calculated the NG culture yield within 30 days and stratified by culture specimen collection sites. RESULTS: The NG culture yield was lowest in the pharynx (37.9%, 95% confidence interval (CI) 36.6-39.2, 1964/5185) followed by the vagina (41.6%, 95% CI 37.0-46.3, 186/447), cervix (60.1%, 95% CI 52.2-67.7, 98/163), rectum (68.0%, 95% CI 66.6-69.3, 3223/4742) and urethra (97.0%, 95% CI 96.4-97.6, 3282/3382). The overall NG culture yield was 77.8% (95% CI 76.8-78.8, 5254/6754) when the culture was performed on the same date as the NAAT test, and it decreased significantly to 53.6% (95% CI 51.5-55.7, 1193/2224) 1-3 days after the NAAT-positive specimens were collected, then to 37.1% (95% CI 30.7-43.7, 83/224) 15-30 days after the NAAT-positive specimens were collected (Ptrend <0.001). CONCLUSIONS: The culture specimen collection sites and time to culture collection influenced the culture yield. NG culture should be performed as close as possible to NAAT testing to improve NG culture yield. In addition, combining molecular resistance testing with culture-based techniques may be necessary to ensure adequate antimicrobial resistance detection.