Impact of rapid susceptibility testing and antibiotic selection strategy on the emergence and spread of antibiotic resistance in gonorrhea

Abstract

Background: Increasing antibiotic resistance limits treatment options for gonorrhea. We examined the extent to which a hypothetical point-of-care (POC) test reporting antibiotic susceptibility profiles could slow the spread of resistance. Methods: We developed a deterministic compartmental model describing gonorrhea transmission in a single-sex population with three antibiotics available to treat infections. Probabilities of resistance emergence on treatment and fitness costs associated with resistance were based on characteristics of ciprofloxacin, azithromycin, and ceftriaxone. We evaluated time to 1% and 5% prevalence of resistant strains among all isolates with: (1) empiric treatment (azithromycin plus ceftriaxone), and treatment guided by POC tests determining susceptibility to (2) ciprofloxacin only and (3) all three antibiotics. Findings: Based on current gonococcal susceptibility patterns in the United States, the model indicated that continued empiric dual antibiotic treatment without POC testing resulted in >5% of isolates being resistant to both azithromycin and ceftriaxone within 15 years. When either POC test was used in 10% of identified cases, this was delayed by 5 years. The three antibiotic POC test delayed the time to reach 1% prevalence of triply-resistant strains by 6 years, while the ciprofloxacin-only test resulted in no delay. Results were less sensitive to assumptions about fitness costs and test characteristics with increasing test uptake. The main limitation of this study is that we made simplifying assumptions to describe gonorrhea transmission and the emergence and spread of resistance in the population. Conclusions: Rapid diagnostics that report antibiotic susceptibility have the potential to extend the usefulness of existing antibiotics for treatment of gonorrhea. Monitoring resistance patterns will be critical with the introduction of such tests.