Transmission of Neisseria gonorrhoeae, the causative agent of gonorrhoea, remains a significant public health challenge. Despite increased access to preventative and therapeutic options, there has been a resurgence in gonorrhoea incidence rates in many countries, accompanied by increasing antimicrobial resistance. In Australia, gonorrhoea is a notifiable disease, with 33,692 notifications reported in 2022; this represents a 141.6% increase in the last decade.
To understand contemporary N. gonorrhoeae transmission in our setting, we carried out an observational study investigating the genetic diversity and antimicrobial resistance of N. gonorrhoeae isolates in Victoria, Australia (January 2017 to July 2021). The study period included 2020-2021 COVID-19 related border closures and other public health restrictions. A hierarchical clustering method based on cgMLST was used to define transmission groups, with an inverse weighting for time between sample collection to accommodate continuing evolution. Additionally, we present phenotypic and genotypic antimicrobial resistance testing data, alongside patient-level demographic and behavioural data. Bayesian statistical methods were applied to measure N. gonorrhoeae genetic diversity throughout the COVID-19 pandemic.
Of 5900 N. gonorrhoeae whole genomes, we identified 230 clusters (n ≥ 3; 4,779), 140 pairs (n = 2; 280 samples) and 841 singletons (n = 1). Individuals with N. gonorrhoeae were typically male (5060/5900; 85.5%), and of those males with reported sexual risk factor data, most identified as men who have sex with men (2206/2410; 91.5%). We observed distinct heterosexual-associated transmission groups, indicative of circulation in different sexual networks. Following COVID-19 public health restrictions, we observed a decrease in genomic diversity, including a decrease in diversity of antimicrobial resistance determinants, although no significant changes in phenotypic resistance.
Our findings have implications for public health including the treatment and prevention of N. gonorrhoeae, with valuable insights for targeted interventions. We observed a considerable shift in the circulating N. gonorrhoeae population and decrease in genomic diversity following COVID-19 lockdowns and border closures, underscoring the importance of ongoing surveillance and adaptation of control strategies. The use of genomics and patient-level data together highlight the complex epidemiological and behavioural factors that drive N. gonorrhoeae transmission, and the necessity for equally sophisticated approaches to prevention and control.