Background: Neisseria gonorrhoeae (Ng) is a public health priority due to the rapid evolution of antimicrobial resistance, the emergence of antibiotic resistance and the absence of a vaccine against Ng. The aim of this study was to investigate trends in the minimum inhibitory concentration (MIC) and resistance (R) or reduced susceptibility (DS) of Ng cases to ceftriaxone (CRO), azithromycin (AZM), tetracycline (TET), benzylpenicillin (PenG), ciprofloxacin (CIP) over a 10-year period.
Methods: Retrospective analysis on an open cohort of Ng cases diagnosed on rectal, urethral and pharyngeal samples at San Raffaele Scientific Institute, between September 2012-February 2023. MICs of antibiotics were determined by gradient-test strips. Bivariate linear regression models, applied on logarithmic MICs values; Cochran-Armitage test was used to determine a linear trend in the proportions of resistant strains.
Results: 436 Ng isolates from 352 individuals were analyzed. MICs of CRO and PenG reduced over time (p < 0.001, p = 0.030), AZM increased (p = 0.001), CIP and TET did not change (p = 0.473, p = 0.272). The percentages of resistant strains were: PenG 89.9%, TET 90.8%, CIP 48.2%, AZM 4.4%; CRO-DS strains were 8.7%, only one CRO-R. The proportion of resistant strains increased over time for AZM (p = 0.007), TET (p = 0.001), CIP (p < 0.001), whereas decreased for PenG (p < 0.001) and CRO-DS/R strains (p < 0.001).
Conclusions: Ng strains showed high susceptibility to CRO, although we identified cases of DS/R and observed high levels of susceptibility to AZM. Overall, the recommended primary regimen for Ng treatment confirmed to be effective.
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