Neisseria gonorrhoeae antimicrobial resistance trends in Portugal over four decades, 1983–2025

Objectives Antimicrobial resistance (AMR) in Neisseria gonorrhoeae, the causative agent of gonorrhoea, represents a global public health challenge due to the pathogen’s remarkable ability to acquire resistance to antimicrobial therapies. In Portugal, the National Institute of Health established the Portuguese National Laboratory Network for Neisseria gonorrhoeae Collection (PTGONONET) in 2010 to monitor nationwide AMR trends and to support surveillance of multidrug-resistant gonococcal strains. The network currently includes 34 geographically distributed public/private laboratories, including the major national private laboratory groups, which voluntarily submit anonymised isolates for centralised antimicrobial susceptibility testing and epidemiological surveillance. This study compiles and updates Portuguese N. gonorrhoeae AMR data collected over four decades (1983–2025), representing the most comprehensive national dataset available to date. Methods 8502 isolates were analysed for susceptibility to azithromycin, benzylpenicillin, cefixime, ceftriaxone, ciprofloxacin, gentamicin, spectinomycin and tetracycline and for β-lactamase production. Most isolates were recovered from males (87.6%) and individuals aged 15–35 years (64.2%), with increasing nationwide coverage observed following PTGONONET implementation. Results Resistance trends showed persistently high resistance to benzylpenicillin and tetracycline, with ~80–90% of isolates resistant since 2016. Ciprofloxacin resistance increased substantially over time and remained consistently high during the last decade, ranging from 40% to 60% of isolates, contrasting sharply with the lower rates observed in the 1980s and 1990s. Azithromycin resistance, initially detected in 1990, remained relatively low until 2018 but increased markedly from 2019 onwards, reaching approximately 40% in both 2022 and 2023. Resistance to extended-spectrum cephalosporins remained sporadic, with only a small number of cefixime- or ceftriaxone-resistant isolates detected since 2019. No resistance to spectinomycin was identified throughout the study period. Increasing gentamicin minimum inhibitory concentrations were observed after 2018. Conclusions These findings highlight the value of long-term nationwide surveillance networks, such as PTGONONET, for monitoring evolving gonococcal AMR patterns, supporting treatment guideline updates and fulfilling international surveillance commitments.