Targeted Culture of Microscopy-Positive Neisseria Gonorrhoeae Specimens Creates Cost-Effective Opportunities for Antimicrobial Susceptibility Surveillance in Both Low- and High-Resource Settings

Background: Neisseria gonorrhoeae has developed antimicrobial resistance (AMR) to all drugs introduced for treatment of gonorrhea. In this serious situation, the World Health Organization (WHO) has published a global action plan and an essential component of this action plan is to substantially enhance the AMR surveillance globally. However, in many settings only microscopy or nucleic acid amplification tests are used for diagnosis. Herein, targeted culture of microscopy-positive N. gonorrhoeae specimens to provide isolates for AMR surveillance was evaluated.

Methods: Stained urogenital smears from 65 male patients (median age: 34.5 years; range: 18-51 years) showing Gram-negative diplococci in microscopy were cultured within three hours. After preparing the microscopy smears, the swabs were placed in a plastic box with a wet paper towel until cultured on selective agar media. Growth was confirmed as N. gonorrhoeae by Gram stained smear, oxidase and superoxol test. Calibrated dichotomous sensitivity (CDS) disc diffusion method and minimal inhibitory concentration (MIC) testing by Etest method was performed on all isolates. Beta-lactamase production was identified with nitrocefin discs. 

Results: N. gonorrhoeae isolates were recovered from 100%, 100%, 97% and 97% of the microscopy-positive samples within 0.5 hour, 1 hour, 2 hours and 3 hours, respectively. The proportions of AMR in N. gonorrhoeae isolates were as follows: ciprofloxacin 96.9%, penicillin G 75.4%, tetracycline 53.8%, and azithromycin 3.1%. No isolates resistant to ceftriaxone, cefixime, cefpodoxime or gentamicin were found, however, 4.6% of isolates showed a decreased susceptibility to all those extended-spectrum cephalosporins and gentamicin. All isolates were susceptible to spectinomycin. Of the gonococcal isolates, 67.7% produced beta-lactamase.

Conclusions: Targeted culture of microscopy-positive N. gonorrhoeae specimens provides cost-effective opportunities for AMR surveillance in both low- and high-resource settings, where culture of N. gonorrhoeae is not used for routine diagnosis. Enhanced AMR surveillance in N. gonorrhoeae globally is crucial for public health purposes.