Metagenomic Analysis of the Gut Microbiota of Wild Mice, a Newly Identified Reservoir of Campylobacter

Abstract

<i>Campylobacter</i>, the most common etiologic agent of zoonotic gastroenteritis in humans, is present in many reservoirs including livestock animals, wildlife, soil, and water. Previously, we reported a novel <i>Campylobacter jejuni</i> strain SCJK02 (MLST ST-8388) from the gut of wild mice (<i>Micromys minutus</i>) using culture-dependent methods. However, due to fastidious growth conditions and the presence of viable but non-culturable <i>Campylobacter</i> spp., it is unclear whether <i>M. minutus</i> is a <i>Campylobacter</i> reservoir. This study aimed to: 1) determine the distribution and proportion of <i>Campylobacter</i> spp. in the gut microbiota of wild mice using culture-independent methods and 2) investigate the gut microbiota of wild mice and the relationship of <i>Campylobacter</i> spp. with other gut microbes. The gut microbiota of 38 wild mice captured from perilla fields in Korea and without any clinical symptoms (18 <i>M. minutus</i> and 20 <i>Mus musculus</i>) were analyzed. Metagenomic analysis showed that 77.8% (14 of 18) of the captured <i>M. minutus</i> harbored <i>Campylobacter</i> spp. (0.24-32.92%) in the gut metagenome, whereas none of the captured <i>M. musculus</i> carried <i>Campylobacter</i> spp. in their guts. Notably, 75% (6 of 8) of <i>M. minutus</i> determined to be <i>Campylobacter</i>-negative using culture-dependent methods showed a high proportion of <i>Campylobacter</i> through metagenome analysis. The results of metagenome analysis and the absence of clinical symptoms suggest that <i>Campylobacter</i> may be a component of the normal gut flora of wild <i>M. minutus</i>. Furthermore, linear discriminant analysis (LDA) showed that <i>Campylobacter</i> was the most enriched genus in the gut microbiota of <i>M. minutus</i> (LDA score, 5.37), whereas <i>Lactobacillus</i> was the most enriched genus in <i>M. musculus</i> (LDA score, -5.96). The differences in the presence of <i>Campylobacter</i> between the two species of wild mice may be attributed to the differential abundance of <i>Campylobacter</i> and <i>Lactobacillus</i> in their respective gut microbiota. In conclusion, the results indicate that wild <i>M. minutus</i> may serve as a potential <i>Campylobacter</i> reservoir. This study presents the first metagenomics analysis of the <i>M. minutus</i> gut microbiota to explore its possible role as an environmental <i>Campylobacter</i> reservoir and provides a basis for future studies using culture-independent methods to determine the role of environmental reservoirs in <i>Campylobacter</i> transmission.