Pharyngeal N. gonorrhoeae infections are believed to contribute to the development of antimicrobial resistance (AMR). However, exact mechanisms behind this remain unknown. Most epidemiological studies showing associations between pharyngeal infections and AMR only include one anatomical location per patient, potentially biasing these results. More information on within-host dynamics is needed to understand the role of extragenital gonorrhoea infections in AMR development. This study aims to gain insight in within-host patterns of gonorrhoea antimicrobial susceptibility, using unique within-person data.
Methods
We used Dutch gonococcal resistance to antimicrobials surveillance (GRAS) data from 2016 to July 2022. Resistance was measured by MIC-values (Minimum Inhibitory Concentration, measured by E-test). We included records with multiple MICs reported at different anatomical locations. We describe the proportion of persons with distinct MICs between two anatomical locations for ceftriaxone, defined as ≥2 MIC dilution difference. Logistic regression analyses were used to identify determinants (demographics and sexual behaviour, e.g. number of partners) of distinct MICs stratified by MSM and women.
Results
A total of 951 persons with multiple MICs were reported (77% MSM, 22% women). In ~20% of persons MICs differed between anatomical locations. Within persons, pharyngeal MICs were more often higher than urogenital MICs (14% [95%CI 9%-21%]) than vice versa (5% [2%-9%]) (n=162). This was not seen between pharyngeal and anorectal MICs (n=503) or anorectal and urogenital MICs (n=374). Regression analyses did not identify predictors of distinct MICs among MSM. Among women, not being tested for STI in the past year (vs. tested negative, aOR 3.73 [95%CI 1.20-11.61]) was associated with distinct MICs. Having a migration background (0.48 [0.22-1.07]) or a partner with migration background (0.37 [0.17-0.78]) were (borderline) protective of distinct MICs.
Conclusions
Distinct MICs between anatomical locations within persons were observed. No behaviours leading to increased STI risk were associated with distinct MICs. An association was found with no recent history of STI testing, which could be a proxy for longer infection duration. These findings might be suggestive of within-host processes leading to shifting MIC-values, rather than, for example, simultaneous infections from different partners. However, further studies explaining the observed within-host MIC differences are needed.
