To Örebro University

Sexually transmitted infections (STIs) are a public health issue of great importance worldwide, with effects on fertility and reproduction. Chlamydia trachomatis and Neisseria gonorrhoeae, causative agents of chlamydia and gonorrhoea, respectively, are the most common bacterial STIs with an estimated 127 million new global cases of chlamydia and 87 million new gonorrhoea cases. The continued emergence of antimicrobial resistance (AMR) in N. gonorrhoeae may in the future lead to an untreatable infection. Prevention of these infections and controlling the development of AMR rely on several strategies developed by the World Health Organization (WHO). This thesis aimed to implement several of these strategies, including supporting vaccine development for C. trachomatis and N. gonorrhoeae, evaluating molecular methods for detecting N. gonorrhoeae, predicting AMR and supporting surveillance of the spread and prevalence of AMR in N. gonorrhoeae. The present studies on a C. trachomatis recombinant vaccine antigen and the investigation of similarities of N. gonorrhoeae antigen amino acid sequences to the antigens included in the meningococcal vaccine 4CMenB contributed to the field of vaccine development for STIs. The assay SpeeDx ResistancePlus® GC performed well in detecting N. gonorrhoeae and predicting ciprofloxacin resistance and could be used in AMR surveillance and individualised treatment. In 2016, the first national genomic surveillance of all N. gonorrhoeae isolates in Sweden was performed. This national surveillance study included whole-genome sequencing combined with phenotypic AMR and epidemiological data, which provides valuable information on circulating strains, epidemiology and phylogeny. Greater knowledge of gonorrhoea and gonococcal AMR epidemiology could inform decisions on guidelines and prevention. It is essential to continue to implement WHO strategies at the national and global levels to prevent and control chlamydia and gonorrhoea infections.