The Wild Mouse (Micromys minutus): Reservoir of a Novel Campylobacter jejuni Strain

Abstract

Campylobacter jejuni is one of the most common zoonotic pathogens worldwide. Although the main sources of human C. jejuni infection are livestock, wildlife can also affect C. jejuni transmission in humans. However, it remains unclear whether wild mice harbor C. jejuni and are involved in the "environment-wildlife-livestock-human" transmission cycle of C. jejuni in humans. Here, we characterized C. jejuni from wild mice and identified genetic traces of wild mouse-derived C. jejuni in other hosts using a traditional approach, along with comparative genomics. We captured 115 wild mice (49 Mus musculus and 66 Micromys minutus) without any clinical symptoms from 22 sesame fields in Korea over 2 years. Among them, M. minutus were typically caught in remote areas of human houses and C. jejuni was solely isolated from M. minutus (42/66, 63.6%). We identified a single clone (MLST ST-8388) in all 42 C. jejuni isolates, which had not been previously reported, and all isolates had the same virulence/survival-factor profile, except for the plasmid-mediated virB11 gene. No isolates exhibited antibiotic resistance, either in phenotypic and genetic terms. Comparative-genomic analysis and MST revealed that C. jejuni derived from M. minutus (strain SCJK2) was not genetically related to those derived from other sources (registered in the NCBI genome database and PubMLST database). Therefore, we hypothesize that C. jejuni from M. minutus is a normal component of the gut flora following adaptation to the gastro-intestinal tract. Furthermore, M. minutus-derived C. jejuni had different ancestral lineages from those derived from other sources, and there was a low chance of C. jejuni transmission from M. minutus to humans/livestock because of their habitat. In conclusion, M. minutus may be a potential reservoir for a novel C. jejuni, which is genetically different from those of other sources, but may not be involved in the transmission of C. jejuni to other hosts, including humans and livestock. This study could form the basis for further studies focused on understanding the transmission cycle of C. jejuni, as well as other zoonotic pathogens originating from wild mice.

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

“…In our previous study, Campylobacter was isolated from mice fecal samples using two different culture methods ( Kim et al., 2020 ). Briefly, homogenized fecal samples (in phosphate-buffered saline—PBS) were directly spread onto modified cefoperazone–deoxycholate agar plates (mCCDA; Oxoid Ltd., Hampshire, United Kingdom) containing the CCDA-selective supplement (Oxoid, Ltd.) and plates were incubated at 42°C for 2 days under microaerobic conditions.…”

“…Although the most common cause of Campylobacter infection is the intake or handling of contaminated poultry, environmental sources such as wildlife, soil, and water are also important infection routes ( Whiley et al., 2013 ; Hofreuter, 2014 ; Skarp et al., 2016 ). As an environmental reservoir, wildlife is an emerging source of Campylobacter infection via the direct transmission of Campylobacter to humans or indirectly via the wildlife-livestock-human cycle ( Kim et al., 2020 ). While the majority of studies on Campylobacter reservoirs in wildlife have been conducted on wild birds, several studies on other hosts, such as deer, boars, and reptiles, have also been conducted ( French et al., 2009 ; Díaz-Sánchez et al., 2013 ; Patrick et al., 2013 ; Carbonero et al., 2014 ).…”

“…Most studies on Campylobacter in wildlife have been conducted using culture-dependent methods, such as the isolation and characterization of bacterial strain ( French et al., 2009 ; Díaz-Sánchez et al., 2013 ; Patrick et al., 2013 ; Carbonero et al., 2014 ). Previously, we reported a novel C. jejuni strain SCJK02 (MLST ST-8388) isolated from fecal samples of wild mice ( Micromys minutus ) ( Kim et al., 2020 ). In the previous study, Campylobacter was isolated from 63% of M .…”

Host-Dependent Clustering of Campylobacter Strains From Small Mammals in Finland

“…To our knowledge, MLST or WGS has only previously been used for typing Campylobacter isolates from small mammals in a South Korean study investigating isolates from M. minutus trapped in sesame fields ( Kim et al, 2020 ), and in a United Kingdom study targeting M. glareolus and A. sylvaticus caught from a woodland habitat and six cattle farms ( Williams et al, 2010 ). Our isolates, including those from M. minutus , differed in all seven loci of the MLST scheme from those reported from South Korea.…”

“…Also, antimicrobial resistance phenotypes can be predicted based on WGS data in Campylobacter species ( Zhao et al, 2015 ). Only a few studies exist worldwide that utilize new methods such as WGS-based typing on Campylobacter isolates from small wild mammals ( Kim et al, 2020 ). Their role as a source of Campylobacter spp.…”