Genotyping of Chlamydia trachomatis detected in South African pregnant women.

Abstract

Background Chlamydia trachomatis (C. trachomatis) is a common cause of bacterial sexually transmitted infections (STIs). The genetic characterisation of C. trachomatis serovars reveals significant genetic diversity in this organism. Untreated C. trachomatis infection in pregnant women has been linked to miscarriage, low birth weight babies, premature rupture of membranes, postpartum endometritis, and transmission to the new-born babies. Currently, there is limited data and analyses on the serovars of C. trachomatis circulating in South African pregnant women. In this study, the prevalence of C. trachomatis infection was determined, and the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of the outer membrane protein gene (omp1) was performed in order to identify the different serovars circulating in the population of pregnant women. Methods In this study, 385 vaginal swab samples were analysed for the presence of C. trachomatis. The swabs were collected from human immunodeficiency virus (HIV)-positive pregnant women at the King Edward VIII hospital in Durban, South Africa. Chlamydia trachomatis was detected using commercial primers and probes (TaqMan Assay, assay ID Ba04646249_s1) which targets the gene encoding the translocated actin-recruiting phosphoprotein of C. trachomatis. Genotyping of C. trachomatis positive samples was performed by an omp1 semi-nested polymerase chain reaction (PCR) assay followed by restriction fragment length polymorphism (RFLP) analysis. The omp1 from C. trachomatis was amplified with gene-specific primers in the first round PCR to yield a 1033 base pair (bp) fragment. Following the first round PCR, 1 μL of the first-round PCR product was used for the semi-nested PCR, amplifying a 978 bp fragment. The 978 bp omp1 amplicons were digested with AluI, DdeI and HinfI, and the banding patterns were compared across the three digests for assignment of serovars. Associations between categorical variables was assessed using chi square (𝑥2) tests. All statistical analysis was conducted using RStudio, version 3.6.3. All p-values were considered significant at < 0.05. Results The actin-recruiting phosphoprotein of C. trachomatis was detected in 47/385 swab samples using the TaqMan Assay. The prevalence of C. trachomatis in the study population was 12.2%. All negative no-template controls did not produce any amplification. Factors associated with testing positive for C. trachomatis included, having a low level of education, being unemployed, being unmarried, not cohabitating with sex partner, early age of first sex, high number of lifetime sex partners, partner having other partners, lack of condom use, lacking symptoms of STIs, lacking treatment for STIs and women having a perceived risk of getting STIs. Serovar E (20/43) - 46.5% was the most frequent serovar in our study population, followed by serovar F (9/43) - 20.9%, G (6/43) - 14.0%, D (5/43) - 11.6%, and the least frequent serovar I (2/43) - 4.7% which was detected in two samples. From the five women that carried serovar D, 20.0% (1/5) reported past treatment of STIs. From the 20 women that carried serovar E, 20.0% (4/20) reported having abnormal vaginal discharge. Of the women with serovar E, 20.0% (4/20) reported past treatment of STIs. From the nine women that carried serovar F, 11.1% (1/9) reported having abnormal vaginal discharge and 22.2% (2/9) reported past treatment of STIs. From the six women that carried serovar G, 16.7% (1/6) reported past treatment of STIs. From the two women that carried serovar I, 50.0% (1/2) reported having abnormal vaginal discharge. Conclusion This study detected an overall 12.2% prevalence rate for C. trachomatis in the pregnant women. The identification of factors associated with infection provided evidence on the importance of antenatal clinics to screen women during their routine check-ups for vaginal infections and provide continuous risk reduction counselling to this vulnerable population. Five different serovars were observed in the studied population with serovars E and F being the most prevalent. The observed diversity of serovars reported within specific populations can be challenging for future vaccine design and development for chlamydia. However, many of the South African serovars detected correlated with serovars found in studies conducted throughout the world. This suggests the possibility of conserved C. trachomatis strains from various geographical areas, which may offer some hope for future vaccine development and diagnostic research aimed at the entire C. trachomatis population.