Phylogenetic analysis of Neisseria gonorrhoeae transmission chains in Copenhagen, Denmark

Background. In the last couple of decades there has been a rise in the incidence of gonorrhoea. This has been the case globally as well as in Denmark. Concurrently, in many countries, antimicrobial resistance (AMR) to most of the antibiotics available for treatment is described in a high percentage of N. gonorrhoeae strains. Therefore, due to this public health issue, N. gonorrhoeae has gained increased attention internationally.A phylogenetic analysis made by whole-genome sequencing (WGS) is a well-known method to describe the genetic relationship between isolates from an organism. With WGS, clusters of N. gonorrhoeae strains can be identified as well as sexual networks if epidemiological data are linked. Furthermore, WGS can detect genotypic AMR, which can support phenotypic AMR surveillance.Aim. This study aimed to make a phylogenetic analysis of 179 gonococcal isolates and to provide knowledge of genotypic AMR used to support phenotypic AMR surveillance of the gonococci.Methods. From 3 April 2018 to 31 October, 179 gonococcal isolates were identified among 157 female and male patients in total attending clinics in Greater Copenhagen, Denmark. Phylogenetic analysis by WGS was performed and single nucleotide polymorphism (SNP) distance matrices were produced by the mapping of reads to the FA 1090 genome (NC_002946). Pairs or triplets of gonococcal isolates from individual patients were compared to each other and the internal SNP distance was noted. Using WGS, genotypic AMR was performed and phenotypic AMR was made by positive culture.Results. Four different sexual networks were identified among the 179 gonococcal isolates. In addition, genotypic AMR of the N. gonorrhoeae strains was detected and compared to the phenotypic AMR of the gonococci.