Comparable gonococcal resistance among PrEP users and non-users in Denmark: a phylogenomic study

Background

Antibiotic resistance in gonococci is a major public health concern and disproportionately affects men who have sex with men (MSM). In Denmark, users of HIV pre-exposure prophylaxis (PrEP) are at increased risk of gonorrhoea, but whether antimicrobial resistance is disproportionately higher among PrEP users warrants investigation. This study assessed the distribution of MSM subgroups across gonococcal clusters and differences in the prevalence of genetic resistance markers.

Methods

We sampled 243 gonococcal isolates from three MSM subgroups: those using pre-exposure prophylaxis (PrEP), MSM living with HIV, and HIV-seronegative MSM not using PrEP. We performed whole genome sequencing to identify clusters and genetic markers associated with antibiotic resistance. Comparing PrEP users to non-users, we used Poisson regression to estimate prevalence ratios for genetic resistance markers as well as phenotypic resistance to ceftriaxone, ciprofloxacin and azithromycin.

Results

Using a 9 SNP threshold, 184 (76%) isolates grouped into 28 clusters, ranging from 2 to 24 isolates in size. Among these, 10 (57%) included isolates from all three MSM subgroups, 16 (67%) from two subgroups, and 2 (7%) from only one subgroup. A Fisher’s exact test showed no evidence that MSM subgroup distribution across clusters differed from random. Comparing PrEP users to non-users, no differences were observed in the prevalence of 67 identified genetic markers or in phenotypic resistance to ceftriaxone, ciprofloxacin, and azithromycin.

Conclusions

Our results indicate that the three MSM subgroups are highly mixed within gonorrhoea clusters. We found no evidence that resistance markers or phenotypic resistance differed between PrEP users and non-users. Efforts to prevent the development of resistant gonococci in MSM should target this population broadly rather than a single subgroup.

Key messages

• MSM subgroups, including PrEP users, are highly mixed within gonococcal transmission clusters, indicating transmission across subgroups rather than within them.

• No differences in genetic or phenotypic antimicrobial resistance were observed between PrEP users and non-users.