Molecular epidemiology of Chlamydia trachomatis

Chlamydia trachomatis infections are the most prevalent bacterial sexually transmitted infections (STT) worldwide. A better understand of the transmission of C. trachomatis may contribute to improved screening and prevention programs in the future and ultimately alleviate this burden. Through the use of various typing methods, better understanding can be achieved by discriminating between clinically, biologically or epidemiologically different C. trachomatis strains. By applying these typing methods in large epidemiological studies, the transmission patterns of these different C. trachomatis strains can be discerned. We evaluated a multilocus sequence typing (MLST) method that was most suitable for molecular epidemiological analysis of C. trachomatis transmission patterns in sexual networks. We used this method in various studies and found major differences between C. trachomatis transmission patterns among heterosexuals and men who have sex with men (MSM). We found that the MSM and heterosexual populations harbour distinct C. trachomatis strains. In addition, within the MSM-associated C. trachomatis strains less variation was observed compared to the heterosexual-associated strains. Among heterosexuals, the distribution of strains varied between countries and between subgroups within one country. This variation was absent among MSM. These differences could arise from biological differences between the risk group-associated strains or can be accounted to differences in the transmission networks between the two risk populations. Future research should elucidate these differences and how these findings can be exploited to improve screening and prevention programs.