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Culture obtained from urethral swab of asymptomatic men who screen positive for Neisseria gonorrhoeae by urine nucleic acid amplification testing
  1. Ayoma Ratnappuli1,
  2. Melanie Bissessor1,
  3. Shehara Arumugam1,
  4. Deborah A Williamson2,
  5. Eric P F Chow1,3,
  6. Christopher K Fairley1,3,
  7. Jason J Ong1,4,
  8. Vesna De Petra2,
  9. Marcus Y Chen1,3
  1. 1 Sexual Health Unit, Melbourne Sexual Health Centre, Alfred Health, Carlton, Victoria, Australia
  2. 2 Melbourne Diagnostic Unit Public Health Laboratory, The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
  3. 3 Central Clinical School, Monash University, Melbourne, Victoria, Australia
  4. 4 Faculty of Medicine Dentistry and Health Sciences, The University of Melbourne, Melbourne, Victoria, Australia
  1. Correspondence to Dr Melanie Bissessor, Melbourne Sexual Health Centre, Carlton VIC 3053, Australia; mbissessor{at}


Background In a previous study of men attending Melbourne Sexual Health Centre who had Neisseria gonorrhoeae detected by urine Aptima Combo 2 (AC2) testing, 11% were asymptomatic. This study aimed to determine whether N. gonorrhoeae can be cultured from asymptomatic men screening positive for N. gonorrhoeae by nucleic acid amplification testing (NAAT) of urine.

Methods Between 1 July 2017 and 31 March 2019, all men attending Melbourne Sexual Health Centre were tested for N. gonorrhoeae by AC2 testing of urine whether urethral symptoms were reported or not. NAAT-positive men were recalled and a urethral swab performed for gonococcal culture using modified Thayer-Martin media with determination of minimum inhibitory concentrations (MICs) by agar dilution.

Results There were 1001 cases (860 individuals) positive for N. gonorrhoeae by urine AC2: 892 (89%) reported urethral symptoms; 109 (11%) did not. Twenty-five asymptomatic cases were excluded because of antibiotic use at or following screening. Of the remaining 84 asymptomatic men, 41 (49%) had a urethral swab performed a median of 5 days after screening. Twenty-one men had urethral discharge at the return visit, 11 of whom reported the discharge at the return visit. Of the 41 men who were swabbed, 31 (76%; 95% CI 60% to 88%) were culture positive for N. gonorrhoeae. Among the 21 men who subsequently developed discharge, 19 (90%; 95% CI 70% to 99%) were culture positive. Among the 20 men who remained asymptomatic, 12 (60%; 95% CI 36% to 81%) were culture positive. MIC profiles were obtained from all isolates.

Conclusions Gonorrhoea was isolated in most but not all asymptomatic men screening positive for N. gonorrhoeae by urine NAAT. Clinicians should consider performing urethral culture in such men to ensure optimal surveillance for antimicrobial resistance. Isolation of N. gonorrhoeae by culture in men without discharge indicates these are true infections with viable organisms.

  • neisseria gonorrhoeae
  • urethritis
  • testing

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  • Handling editor Nigel Field

  • Twitter @drdebwilliamson, @EricPFChow

  • Contributors MB, SA, AR and MYC designed and conceived the study and are responsible for the overall content of the study. DAW and VDP were involved in laboratory testing. MB, SA and AR wrote the first draft of the manuscript. MB, SA and AR performed the statistical analyses. MB, SA and AR performed chart review and prepared the tables. DAW and VDP oversaw the laboratory testing. DAW provided resources for laboratory testing. All authors were involved in data interpretation and contributed to the final version of the manuscript.

  • Funding EPFC and DAW are supported by an Australian National Health and Medical Research Council (NHMRC) Emerging Leadership Investigator Grant (GNT1172873 and GNT1174555, respectively). CKF is supported by Australian NHMRC Leadership Investigator Grants (GNT1172900).

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.