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

Antimicrobial resistance (AMR) is a serious public health threat. 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 the number of ceftriaxone non-susceptible infections. There is an urgent need for better interpretation and use of surveillance data to estimate the prevalence of resistance. In this modeling study, we simulated the spread of a new strain of ceftriaxone non-susceptible gonorrhea in a population of 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 by the time the non-susceptible strain was discovered and (ii) the likelihood of strain persistence in the absence of newly reported cases. Upon detection of one ceftriaxone non-susceptible isolate, the undetected disease burden was an estimated 5.4 infections with substantial uncertainty (0-18 infections, 95% uncertainty interval). In the absence of additional reports of ceftriaxone non-susceptible infections over the subsequent 180 days, the estimate declined to 2.5 infections with a narrower uncertainty interval (0-10 infections). The likelihood of ongoing transmission also declined from 66% (26-86%) at first detection to 2% (0-10%) after 180 days. Enhanced monitoring of the magnitude and trends of AMR is a key priority to reduce the burden of resistance and extend the useful lifespan of last-line antibiotics.