Molecular characteristics of the ompA gene of serotype B Chlamydia trachomatis in Qinghai Tibetan primary school students

Abstract

To study the molecular characteristics of Chlamydia trachomatis, the major outer membrane protein gene (ompA) of C. trachomatis from primary school students with trachoma residing in the Qinghai Tibetan area was sequenced and compared with the same serotype in GenBank. In Jianshetang Primary School and Galeng Central Primary School in the Galeng Tibetan Township of Qinghai Haidong Sala Autonomous County, scraped samples were collected from the upper tarsal conjunctiva and lower conjunctival sac of both eyes of 45 students with trachoma, stored at 4°C, and transported to Beijing Tongren Hospital by air within 24 h. The samples were screened for C. trachomatis by real-time PCR. The ompA gene from the C. trachomatis-positive samples was amplified by nested PCR. The serotype was confirmed by National Center for Biotechnology Information (NCBI) BLAST search and homology analysis. The entire ompA gene sequence was compared with the corresponding gene sequences of serotype B strains available in GenBank. Of the 45 students aged 6-13 years with trachoma, 26 C. trachomatis-positive students were identified by the initial real-time PCR screening (average age, (9.09±1.63) years; sex ratio, 1.0), accounting for 57.78% (26/45). The cycle threshold values for real-time PCR were 16.79-37.77. Half (13/26) of C. trachomatis-positive students had a bacterial copy number of >10 5 . The compliance rate of the ompA gene sequences with the C. trachomatis serotype B strains in GenBank was up to 99%. Two novel genetic mutations were found when the ompA gene was compared with those of the 11 serotype B strains in GenBank. The two non-synonymous mutations were located at (i) position 271 in the second constant domain, an adenine (A) to guanine (G) substitution (ACTGCT), changing the amino acid at position 91 from threonine to alanine (ThrAla) in all 26 strains; and (ii) position 887 in the fourth variable domain, a cytosine (C) to thymine (T) substitution (GCAGTA), changing the amino acid at residue 296 from alanine to valine (AlaVal) in four of the 26 strains. Six mutations were identified relative to ATCC VR-573. The strains could be divided into two gene clusters according to the mutation at nucleotide position 887: CQZ-1 (China Qinghai Tibetan-1) and CQZ-2 (China Qinghai Tibetan-2). We thus detected two novel serotype B mutant strains of C. trachomatis among study subjects with trachoma.Chlamydia trachomatis, major outer membrane protein gene, sequencing, homology analysis Citation:

Survey, Culture, and Genome Analysis of Ocular Chlamydia trachomatis in Tibetan Boarding Primary Schools in Qinghai Province, China

“…A total of 115 trachoma swabs from each conjunctiva with one or more follicles and the corresponding conjunctival sac were collected. All samples were examined using a commercial qPCR kit detecting chlamydial plasmid and ompA sequencing for qPCR-positive conjunctiva swabs was performed, as previously described (Li et al, 2016; Wang N. et al, 2016). Forty-five swabs from 26 students were qPCR-positive for C. trachomatis infection and two type-B ompA variants were identified.…”

“…Li et al previously reported the identification of two type-B ompA variants in 37 qPCR-positive conjunctival samples (Li et al, 2016). Here, we report the finding of another ompA variant in a single sample of no.…”

“…Children resident in boarding schools investigated in this study were found to have clinical evidence of active trachoma (conjunctival lymphoid follicles) during this survey. Thus, a complete trachoma screening and sampling was performed in order to understand the prevalence and etiology of trachoma in these schools (Li et al, 2016; Wang M. et al, 2016). The Wang group identified 45 cases of follicular conjunctivitis, 26 of them were infected with ompA genovar B C. trachomatis , and identified other potential follicle-causing bacteria in both C. trachomatis -positive and—negative cases (Li et al, 2016; Wang, 2016; Wang M. et al, 2016; Wang N. et al, 2016).…”

“…Thus, a complete trachoma screening and sampling was performed in order to understand the prevalence and etiology of trachoma in these schools (Li et al, 2016; Wang M. et al, 2016). The Wang group identified 45 cases of follicular conjunctivitis, 26 of them were infected with ompA genovar B C. trachomatis , and identified other potential follicle-causing bacteria in both C. trachomatis -positive and—negative cases (Li et al, 2016; Wang, 2016; Wang M. et al, 2016; Wang N. et al, 2016). Their identification of non-chlamydial bacteria in clinically identified cases of follicular trachoma is congruent with other studies (Burton et al, 2011; Burr et al, 2013).…”

“…Swab samples of conjunctivas (left and right eye) or conjunctival sacs from trachoma patients and non-trachoma students were collected as previously described (Li et al, 2016). All swabs were stored in ice boxes in the field and were transported to laboratories by air within 48 h of collection.…”