Chlamydia trachomatis Strains Show Specific Clustering for Men Who Have Sex with Men Compared to Heterosexual Populations in Sweden, the Netherlands, and the United States

Abstract

f High-resolution genotyping of Chlamydia trachomatis improves the characterization of strains infecting different patient groups and sexual networks. In this study, multilocus sequence typing (MLST) and ompA sequence determination were used for an analysis of C. trachomatis strains from 203 men who have sex with men (MSM) from Sweden, the Netherlands, and the United States. The results obtained were compared with data from 153 heterosexual women from Sweden and the Netherlands. The overlap in MLST/ompA profiles between MSM from Sweden and the Netherlands was 68%, while the overlap between heterosexual populations from these countries was only 18%. The distribution of genotypes in MSM from the United States was less similar to that in MSM from the European countries, with 45% and 46% overlaps for MSM in Sweden and the Netherlands, respectively. Minimum-spanning-tree analysis of MLST/ompA sequence types identified two large clusters that contained almost exclusively samples from MSM and comprised 74% of all MSM samples. Three other clusters were predominated by samples from women but also contained MSM specimens. Of 19 detected variants of the MLST target CT144, three variants were highly associated with MSM. Our study supports the hypotheses of both tissue tropism as well as epidemiological network structures as explanations for the linkage between specific genetic variants and sexual orientation.

Global Multilocus Sequence Type Analysis of Chlamydia trachomatis Strains from 16 Countries

“…The obtained index was well above 0.95, an "ideal" cutoff value for a molecular typing method (38). The lower D for the predominating clusters in Table 1 is explained by the inclusion of some epidemiologically related samples, especially among MSM who may be connected via extended international sexual networks (15,19).…”

“…The third scheme was developed by Klint et al (10); it is intended for short-term clinical epidemiology and outbreak investigations and is based on five highly variable genomic loci (hctB [CT046], CT058, CT144, CT172, and pbpB [CT682]). The MLST scheme has been slightly modified to facilitate rational processing with only 1% loss of discriminatory capacity (13), and the current setup can be found at the Uppsala University C. trachomatis MLST database (http: //mlstdb.bmc.uu.se).Since its development in 2007, the scheme has been applied to a variety of clinical specimens, including samples from cases of urogenital chlamydia (7,(13)(14)(15)(16)(17)(18)(19)(20)(21), LGV (22,23), and trachoma (24). It has been useful for different purposes: (i) identification of clonal spread of LGV (22) …”

“…It has been useful for different purposes: (i) identification of clonal spread of LGV (22) and the new variant of C. trachomatis (16,17); (ii) differentiation of strains within the predominating serotype, E (7,17); (iii) differentiation of strains infecting men who have sex with men (MSM) and heterosexuals (15,19); (iv) investigation of the role of tissue tropism (21); and (v) molecular epidemiology and antibiotic treatment of trachoma (24). At present, our database comprises 415 unique sequence types (STs) derived from 2,089 C. trachomatis specimens.…”

“…Since its development in 2007, the scheme has been applied to a variety of clinical specimens, including samples from cases of urogenital chlamydia (7,(13)(14)(15)(16)(17)(18)(19)(20)(21), LGV (22,23), and trachoma (24). It has been useful for different purposes: (i) identification of clonal spread of LGV (22) …”

“…Since its development in 2007, the scheme has been applied to a variety of clinical specimens, including samples from cases of urogenital chlamydia (7,(13)(14)(15)(16)(17)(18)(19)(20)(21), LGV (22,23), and trachoma (24). It has been useful for different purposes: (i) identification of clonal spread of LGV (22) and the new variant of C. trachomatis (16,17); (ii) differentiation of strains within the predominating serotype, E (7,17); (iii) differentiation of strains infecting men who have sex with men (MSM) and heterosexuals (15,19); (iv) investigation of the role of tissue tropism (21); and (v) molecular epidemiology and antibiotic treatment of trachoma (24).…”