Molecular detection of Campylobacter species from human and cattle faecal samples in Kilosa District, Tanzania

Abstract

A growing number of Campylobacter species other than C. jejuni and C. coli have been considered as emerging human and animal pathogens but their contribution to human gastroenteritis is poorly documented. This study aimed at detecting Campylobacter species from human and cattle faecal samples in Kilosa District, Tanzania using molecular techniques without culture. Seventy (70) faecal samples were collected from five diarrheic and 65 non-diarrheic human patients attending Kilosa District Hospital in Tanzania from July to October 2019. During the same period, 30 faecal samples were also collected from healthy cattle in the same district. Genus and species identification of Campylobacter was conducted on the samples using molecular techniques [the polymerase chain reaction (PCR) and 16S rRNA sequencing]. Phylogenetic analysis was carried out by comparison of the 16S rRNA gene sequences to reference strains by the Neighbor-Joining method in MEGA X. Campylobacter species detection rate by PCR was 65.7% (46/70) and 20% (6/30) in humans and cattle, respectively.  There were five human diarrheic cases, four of which were positive for Campylobacter and of these, two were children ≤15 years of age. In humans, 16S rRNA sequencing revealed that C. concisus was the most predominant species occurring at a frequency of 37.8% (14/37), followed by uncultured Campylobacter spp. 24.3% (9/37) and C. hominis 21.6% (8/37). The least represented species were C. jejuni and C. lanienae, all occurring at 2.7% (1/37). In cattle, five (100%) sequenced PCR products matched with C. lanienae. Phylogenetic analysis revealed that with the exception of C. lanienae, 16S rRNA sequences of Campylobacter species were closely related to the reference strains used (Percent identity: 90.51-96.56%). Based on our findings, we recommend that molecular techniques, mainly PCR be adopted for the direct detection of Campylobacter species during laboratory screening and surveillance studies.