No abstract

Urogenital infection due to Chlamydia trachomatis (CT) is one of the most common bacterial sexually transmitted infections (STIs) and is a major public health problem worldwide. Molecular characterisation of CT is important for understanding the pathophysiological mechanisms of chlamydial disease and its transmission dynamics in sexual networks. Traditionally, strain typing of CT was based on serotyping methods characterising the major outer membrane protein (MOMP). With the advent of polymerase chain reaction and sequencing the era of molecular typing began. Molecular characterization of CT strains is based on sequence analysis of ompA gene encoding MOMP. However, in due course of time, improvements were made to enhance the discriminatory power of sequencing and quality of epidemiological information. New high-resolution genotyping methods using multiple loci such as multilocus sequence typing (MLST) and multiple loci variable number of tandem repeats (MLVA) were developed but were unable to differentiate mixed infections (MIs). The development of DNA-hybridisation methods emerged as a major breakthrough in detecting MIs. Although MLST and MLVA are more discriminative than other genotyping methods, they are laborious and expensive. DNA microarray technique is an affordable alternative for genotyping. Since recombination is widespread in the CT genome, ompA is not a reliable marker for phylogenetic studies; hence, whole genome sequencing may provide maximum phylogenetic resolution of CT strains. A descriptive review is provided of the various molecular CT typing methods. The vital information gained can be used for formulating screening programmes, targeted prevention and optimising therapeutic measures aiming to reduce disease transmission.

To determine the prevalence and distribution of Chlamydia trachomatis genovars in patients with infertility by PCR-RFLP and ompA gene sequencing. Prevalence of other etiological agents (viz., Ureaplasma spp. and Mycoplasma hominis) were also assessed. Endocervical swabs were collected from 477 women and urine was collected from 151 men attending the Infertility Clinic. The samples were screened for C. trachomatis by cryptic plasmid, ompA gene and nested ompA gene PCR. Genotyping was performed by PCR-RFLP and sequencing. Samples were screened for Ureaplasma spp. and M. hominis. The prevalence of C. trachomatis in infertile women and their male partners were 15.7% (75 of 477) and 10.0% (15 of 151) respectively. Secondary infertility was significantly associated with chlamydial infection. Genovar E was the most prevalent followed by genovar D and F. Twenty-four C. trachomatis strains were selected for ompA gene sequencing. No mixed infection was picked. Variability in ompA sequences was seen in 50.0%. Both PCR-RFLP and ompA gene sequencing showed concordant results. High prevalence of C. trachomatis in infertile couples warrants routine screening for C. trachomatis infection in all infertile couples. Genotyping of the ompA gene of C. trachomatis may be a valuable tool in understanding the natural history of C. trachomatis infection.