Molecular epidemiology and pharmacokinetic-pharmacodynamic analysis of Neisseria gonorrhoeae strains in Northern Spain.

PURPOSE: To analyse the epidemiology, antimicrobial susceptibility and molecular diversity of Neisseria gonorrhoeae isolates recovered in 2016-2017 at a tertiary hospital in northern Spain, and to perform a seven-year pharmacokinetic/pharmacodynamic (PK/PD) evaluation using susceptibility data from previous studies conducted in the same hospital setting.

METHODS

A total of 231 non-duplicated isolates from 227 patients were studied. Antimicrobial susceptibility was determined by MIC gradient strip tests and molecular typing was performed by NG-MAST v2.0. Epidemiological variables were analysed, and considering the MIC distribution of the isolates, the cumulative fraction of response (CFR) for relevant antimicrobials was estimated.

RESULTS

Most infections occurred in men (80.5%), particularly among men who have sex with men (50.3%), with the highest incidence in patients aged 25-34 years. All isolates were susceptible to ceftriaxone and cefixime (100%), while susceptibility to azithromycin remained above 95% throughout the study period. In contrast, ciprofloxacin resistance remained high, ranging from 46.2% to 72.7% over the seven-year period. PK/PD analysis showed that CFR values ≥ 90% were achieved only with cephalosporins. Molecular typing identified 91 STs, including 15 previously undescribed STs. Six genogroups accounted for 51.9% of isolates and were associated with distinct epidemiological and resistance patterns.

CONCLUSION

Ceftriaxone remains the preferred empirical treatment option for gonococcal infection. The favourable PK/PD performance observed for cefixime supports its activity against the studied isolates, although current treatment recommendations continue to prioritize ceftriaxone, particularly for extragenital infections; whereas ciprofloxacin should not be recommended for empirical use because of persistently high resistance rates. Continued molecular and antimicrobial resistance surveillance is essential for monitoring the emergence and dissemination of NG-MAST genogroups associated with antimicrobial resistance and for guiding future treatment strategies.