Background: CDC recommends test-of-cure (TOC) for persons with pharyngeal gonorrhea (GC) by culture or nucleic acid amplification test (NAAT) 7–14 days after initial treatment. We investigated the yield of routine pharyngeal GC TOC to detect treatment failures through the multi-site Pharyngeal Gonorrhea TOC Project.
Methods: During May 1, 2021–July 31, 2022, four U.S. public STD Clinics implemented pharyngeal GC TOC. Implementation varied by jurisdiction; all sites collected demographic, clinical, and behavioral data on all pharyngeal GC and positive TOC cases using a standardized data-collection form. Clinicians dispositioned cases with the suspected reason for positive TOC as follows: (1) re-infection (any sexual activity in interim), (2) false positive due to residual genetic material (negative repeat test prior to re-treatment), (3) treatment failure due to non-recommended treatment, (4) treatment failure after recommended treatment (with or without cephalosporin resistance).
Results: The four sites diagnosed 1,968 pharyngeal GC infections during the study period. The majority (90.3%) received recommended treatment (ceftriaxone). Among 1,829 treated cases, 45.7% (n=836) returned for TOC, which varied by site (range: 35.5%– 70.8%). Median time between treatment and TOC was 14 days (interquartile range: 14–18). Among those with TOC, 4.7% (n=39) were positive by NAAT. Of these, 48.7% had culture attempted; six positive TOC (15.4%) were also positive by culture. Most positive TOC (64.1%) were attributed to re-infection (n=12) or false positive results (n=13). Eight (20.5%) were treatment failures: two due to non-recommended treatment (gentamicin plus azithromycin), and six failed recommended treatment. Of the six that failed recommended treatment, four had positive GC culture, of which two had antimicrobial susceptibility testing results indicating ceftriaxone susceptibility. Six positive TOC (15.4%) could not be dispositioned due to missing data (i.e., lost-to-follow-up).
Conclusion: Routine pharyngeal GC TOC identified 5% of tested cases with positive TOC, though ceftriaxone treatment failure was rare (< 1%), and there were no cases of cephalosporin-resistant GC. However, low return rates and a lack of culture from over half of positive GC TOC cases highlight the challenges of determining the cause of a positive GC TOC, and the limitations of routine pharyngeal TOC to identify cephalosporin resistance.
