Estimating the undetected burden and the likelihood of strain persistence of drug-resistant Neisseria gonorrhoeae

Neisseria gonorrhoeae has developed resistance to all antibiotics recommended for treatment and reports of reduced susceptibility to ceftriaxone, the last-line treatment, are increasing. Since many asymptomatic infections remain undiagnosed and most diagnosed infections do not undergo antibiotic susceptibility testing, surveillance systems may underestimate resistant infections. In this modeling study, we simulated the spread of a new strain of ceftriaxone non-susceptible N. gonorrhoeae in a population comprising men who have sex with men as well as heterosexual men and women. We compared scenarios with varying strain characteristics and surveillance capacity. For each scenario, we estimated (i) the number of undetected infections of the novel strain and (ii) the likelihood of strain persistence in the absence of newly reported cases. Upon detection of one non-susceptible isolate, the undetected burden was an estimated 5.4 infections with substantial uncertainty (0-18 infections, 95% uncertainty interval). Without additional reports of non-susceptible infections over the subsequent 180 days, the estimate declined to 2.5 infections (0-10 infections). The likelihood of ongoing transmission also declined from 66% (26-86%) at first detection to 2% (0-10%) after 180 days. To extend the useful lifespan of last-line antibiotics, our model estimated the infection landscapes that could underlie data from surveillance systems.