In China, Chlamydia trachomatis infections are endemic in the general population, but most infections are found in specific risk groups, such as female sex workers. The most prevalent C. trachomatis genovar strains, as defined by ompA genotyping, were described to be E, D, and F, which are also common in high risk groups in other parts of the world. We wondered whether by using high resolution multilocus sequence typing (MLST) we could distinguish distinct new CT strains in China

In this study we investigated Chinese strains from 101 heterosexual visitors of the sexually transmitted infections (STI) clinic in Nanjing using MLST. These strains were compared with 256 typed strains from heterosexual visitors of the STI clinic in Amsterdam, the Netherlands. Epidemiological data were obtained from structured questionnaires.

Full MLST data were obtained for 90 samples from 58 men and 32 women from Nanjing, showing 34 sequence types. These types were dispersed over 5 C. trachomatis clusters in a minimum spanning tree. When combining MLST data from the Chinese samples with the Dutch samples, distinct new clusters for Nanjing appeared, but some Chlamydia strains clustered with and thus were identical to those from Amsterdam. More than half of the Nanjing participants paid or received money for sex in the previous 6 months. None of the patient characteristics was related to a specific Chlamydia cluster. High resolution typing revealed both distinct and shared C. trachomatis strains in China. These shared strains proved to be highly prevalent among heterosexuals in all countries investigated so far, using this MLST typing. Geographical variation in circulating C. trachomatis strains could not have been detected using ompA genotyping only.