Campylobacter sputorum subsp. bovis subsp. nov., isolated from cattle, and an emended description of Campylobacter sputorum

Authors: Miller, William - Bill; Williams, Tina; Wood, Delilah - De; Chapman, Mary

Submitted to: International Journal of Systematic and Evolutionary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Strains of the species Campylobacter are commonly associated with human illness. Campylobacter jejuni is considered the leading cause of bacterial human gastroenteritis worldwide. In addition to C. jejuni, other Campylobacter species have also been linked with disease in both humans and livestock. One such species, Campylobacter sputorum, has been recovered from cattle, sheep and swine, and occasionally from humans, where it may be an infrequent cause of human illness. Six C. sputorum strains were recovered exclusively from cattle. Although placed within C. sputorum using standard lab tests, they were noticeably different from classical C. sputorum strains. DNA sequencing analysis and other analyses indicated that while they were C. sputorum, their differences warranted creation of a subspecies within C. sputorum, for which the name C. sputorum subsp. bovis is proposed. Existing C. sputorum strains would therefore be moved into a second novel C. sputorum subspecies, the newly created C. sputorum subsp. sputorum. Simple lab tests can be readily performed to distinguish members of the two subspecies. The capacity of these strains to cause illness in either livestock or humans is currently unknown but warrants further investigation, as their genetic background suggests potential virulence.

Technical Abstract: Six urease-negative Campylobacter strains were isolated from cattle feces over a 19-month time period from 2009 to 2010. These strains were initially identified as Campylobacter sputorum by 16S rRNA gene and atpA typing. Initial studies characterizing these strains by multi-locus sequence typing and genome sequencing further supported their classification as C. sputorum but indicated that these strains form a divergent clade within the species. A polyphasic study was undertaken here to clarify their taxonomic position. Phylogenetic analyses were performed based on 16S rRNA gene sequences and the concatenated sequences of 330 core genes, with the latter analysis also placing the six strains into a clade distinct from the three C. sputorum biovars. Pairwise digital DNA-DNA hybridization values identified these strains as C. sputorum, and pairwise average nucleotide identity values were consistent with those observed between current Campylobacter subspecies pairs. Standard phenotypic testing was also performed. All strains are microaerobic, anaerobic, motile, Gram-negative, spiral cells that are oxidase and catalase positive. Strains can be distinguished from the C. sputorum biovars by the presence of alkaline phosphate activity and TTC reduction and absence of nitrate reduction. The data presented here show that these strains represent a novel subspecies within Campylobacter sputorum, for which the name Campylobacter sputorum subsp. bovis subsp. nov. (type strain =RM8705T, =LMG 32300T, =CCUG 75470T) is proposed. This description would create a second subspecies Campylobacter sputorum subsp. sputorum subsp. nov., comprising the biovars sputorum, fecalis and paraureolyticus (type strain = LMG 7795T, =CCUG 9728T).