Abstract
Investigations of the impact that patent infections by soil-transmitted gastrointestinal nematode parasites exert on the composition of the host gut commensal flora are attracting growing interest by the scientific community. However, information collected to date varies across experiments, and further studies are needed to identify consistent relationships between parasites and commensal microbial species. Here, we explore the qualitative and quantitative differences between the microbial community profiles of cohorts of human volunteers from Sri Lanka with patent infection by one or more parasitic nematode species (H+), as well as that of uninfected subjects (H-) and of volunteers who had been subjected to regular prophylactic anthelmintic treatment (Ht). High-throughput sequencing of the bacterial 16S rRNA gene, followed by bioinformatics and biostatistical analyses of sequence data revealed no significant differences in alpha diversity (Shannon) and richness between groups (P = 0.65, P = 0.13 respectively); however, beta diversity was significantly increased in H+ and Ht when individually compared to H-volunteers (P = 0.04). Among others, bacteria of the families Verrucomicrobiaceae and Enterobacteriaceae showed a trend towards increased abundance in H+, whereas the Leuconostocaceae and Bacteroidaceae showed a relative increase in H- and Ht respectively. Our findings add valuable knowledge to the vast, and yet little explored, research field of parasite—microbiota interactions and will provide a basis for the elucidation of the role such interactions play in pathogenic and immune-modulatory properties of parasitic nematodes in both human and animal hosts.
Highlights
Rarefaction curves generated following in silico subtraction of low-quality and contaminant sequences indicated that the majority of faecal bacterial communities were represented in the remaining sequence data, allowing us to undertake further analyses
Data from this study augments current knowledge of the effect that helminth infections and continued prophylactic treatment exert on the composition of the gut microbiota of the human host
Our relatively small sample size, dictated by the prevalence of helminth infections in the Sri Lankan community enrolled in this investigation, may have affected our statistical power; in addition, dietary variabilities, as well as differences in species of infecting helminths and parasite loads, while effectively representing a ‘real world’ scenario, may have introduced a range of confounding factors that, under the circumstances of this study, we were unable to fully evaluate
Summary
Ethics statementThis study was approved and carried out in strict accordance and compliance with the guidelines of the Institutional Ethical Review Committee, Faculty of Medicine, University of Peradeniya, Sri Lanka (Research Project No 2015/EC/58). Subjects were both men and women, of varying ages and social background, with no reported symptoms of GI disease or any other concomitant diseases, and who had not received antibiotic treatment over at least 6 months prior to the study (Table 1). Participants from the villages of Rangala, Lolgama, Elagolla, Lunugala and Hanthana were workers in tea estates, while those from Kandakuliya and Valalai were fishermen (cf Fig 1). Subjects from Mawanella and Akurana were living in congested urban areas characterised by poor sanitary living conditions. All participants were interviewed directly by YR, PKP and RSR using a standardised, pre-tested questionnaire aimed to identify means of access to water, knowledge of sanitary and hygiene standards, availability of and access to health care facilities, awareness of risks of infection by GI helminths, and frequency of anthelmintic treatments. A copy of the questionnaire is provided in S1 Fig
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