Molecular epidemiology of genital Chlamydia trachomatis infection in high-risk women in Senegal, West Africa

Abstract

The prevalence and heterogeneity of Chlamydia trachomatis infections in a cohort of female sex workers in Dakar (Senegal) were determined by using endocervical-swab-based PCR DNA amplification assays. The overall prevalence of cervical chlamydial infection was 28.5% (206 of 722), and most of these infections were asymptomatic. An increased number of sexual partners was significantly associated with infection (adjusted odds ratio [AOR] = 1.37; 95% confidence interval [CI] = 1.06 to 1.77), while the presence of a yeast infection was negatively associated with chlamydial infection (AOR = 0.28; 95% CI = 0.10 to 0.83). Six different C. trachomatis genotypes were identified based on phylogenetic analysis of the omp1 gene sequences. Interestingly, genotype E predominated (47.6%) and was not associated with visible signs of cervical inflammation compared to non-E genotypes (P < 0.05). Overall, the high rate of asymptomatic C. trachomatis infection by genotype E may suggest genotype-specific properties that confer a transmission advantage in this high risk population.

FIG. 1

Phylogenetic tree based on the nucleotide sequence of the omp1 gene variable domains from 49 strains. The neighbor-joining tree was prepared by using the Kimura's two-parameter method and by removing positions at which gaps were created. Taxa in boldface represent the sequences from the 21 strains from this study and are denoted by their identification number. Other taxa are sequences obtained from previously published studies (, , , , , , , , –36, 47, 48). Branch lengths are proportional to the sequence divergence between taxa in the tree, as illustrated by the scale bar. Numbers at the nodes indicate bootstrap values, based on 1,000 bootstrap replicates. DNA sequence homology groups are labeled as classes B, C, and intermediate.