Detection of Chlamydiaceae and Chlamydia-like organisms on the ocular surface of children and adults from a trachoma-endemic region

Ehsan Ghasemian,Gilbert Greub,Balgesa Elkheir Babiker,Elisabeth Stein,Florian Tagini,Aleksandra Inic-Kanada,Hadeel Alchalabi,Darja Keše,Astrid Collingro,Nadine Schuerer,Nicole Borel,Talin Barisani-Asenbauer

doi:10.1038/s41598-018-23887-1

Abstract

Trachoma, the leading infectious cause of blindness, is caused by Chlamydia trachomatis (Ct), a bacterium of the phylum Chlamydiae. Recent investigations revealed the existence of additional families within the phylum Chlamydiae, also termed Chlamydia-like organisms (CLOs). In this study, the frequency of Ct and CLOs was examined in the eyes of healthy Sudanese (control) participants and those with trachoma (case). We tested 96 children (54 cases and 42 controls) and 93 adults (51 cases and 42 controls) using broad-range Chlamydiae and Ct-specific (omcB) real-time PCR. Samples positive by broad-range Chlamydiae testing were subjected to DNA sequencing. Overall Chlamydiae prevalence was 36%. Sequences corresponded to unclassified and classified Chlamydiae. Ct infection rate was significantly higher in children (31.5%) compared to adults (0%) with trachoma (p < 0.0001). In general, 21.5% of adults and 4.2% of children tested positive for CLOs (p = 0.0003). Our findings are consistent with previous investigations describing the central role of Ct in trachoma among children. This is the first study examining human eyes for the presence of CLOs. We found an age-dependent distribution of CLO DNA in human eyes with significantly higher positivity in adults. Further studies are needed to understand the impact of CLOs in trachoma pathogenicity and/or protection.

Highlights

Trachoma constitutes the leading infectious cause of blindness worldwide[1]
All the nucleic acid extraction negative controls and real-time polymerase chain reaction (PCR) negative controls remained negative when tested with Chlamydiae real-time PCR
No swab has been taken as a field control, the risk of contamination can be ruled out because of existing differences in the distribution of positive samples for Chlamydiae real-time PCR and various profiles of sequences corresponding to different Chlamydiae families among children and adults as well as cases and controls

Summary

Introduction

Trachoma constitutes the leading infectious cause of blindness worldwide[1]. It is considered a public health problem in 41 countries and is responsible for the visual impairment of approximately 1.9 million people, of whom 0.450 million are blind[2]. Results from two separate studies in Tanzania, one, a cross-sectional study on children[30] and the other a case-control study on adults[31], revealed a strong association between non-chlamydial bacterial infections (such as Streptococcus pneumoniae and Haemophilus influenza) and clinical signs of trachoma in children and adults. Trichiasis, the introversion of the eyelashes, has been described repeatedly as a direct route for conjunctival colonization with pathogens in the eyes of patients with trachoma[34,35] Such surveys provide insights into the possible role of various chlamydial species on ocular surface pathogenicity. The main aim of this case-control study was to investigate the frequency of C. trachomatis and other Chlamydiae in ocular samples of children and adults from Al Qadarif region in Sudan (Fig. 1) with trachoma and healthy participants

Methods

Results

Conclusion