AUTHOR=Cunha Federico , Zhai Yuting , Casaro Segundo , Jones Kristi L. , Hernandez Modesto , Bisinotto Rafael S. , Kariyawasam Subhashinie , Brown Mary B. , Phillips Ashley , Jeong Kwangcheol C. , Galvão Klibs N. 

TITLE=Pangenomic and biochemical analyses of Helcococcus ovis reveal widespread tetracycline resistance and a novel bacterial species, Helcococcus bovis

JOURNAL=Frontiers in Microbiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1456569

DOI=10.3389/fmicb.2024.1456569

ISSN=1664-302X

ABSTRACT=<p><italic>Helcococcus ovis</italic> (<italic>H. ovis</italic>) is an opportunistic bacterial pathogen of a wide range of animal hosts including domestic ruminants, swine, avians, and humans. In this study, we sequenced the genomes of 35 <italic>Helcococcus</italic> sp. clinical isolates from the uterus of dairy cows and explored their antimicrobial resistance and biochemical phenotypes <italic>in vitro</italic>. Phylogenetic and average nucleotide identity analyses classified four <italic>Helcococcus</italic> isolates within a cryptic clade representing an undescribed species, for which we propose the name <italic>Helcococcus bovis</italic> sp. nov. By establishing this new species clade, we also resolve the longstanding question of the classification of the Tongji strain responsible for a confirmed human conjunctival infection. This strain did not neatly fit into <italic>H. ovis</italic> and is instead a member of <italic>H. bovis</italic>. We applied whole genome comparative analyses to explore the pangenome, resistome, virulome, and taxonomic diversity of the remaining 31 <italic>H. ovis</italic> isolates. An overwhelming 97% of <italic>H. ovis</italic> strains (30 out of 31) harbor mobile tetracycline resistance genes and displayed significantly increased minimum inhibitory concentrations of tetracyclines <italic>in vitro</italic>. The high prevalence of mobile tetracycline resistance genes makes <italic>H. ovis</italic> a significant antimicrobial resistance gene reservoir in our food chain. Finally, the phylogenetic distribution of co-occurring high-virulence determinant genes of <italic>H. ovis</italic> across unlinked and distant loci highlights an instance of convergent gene loss in the species. In summary, this study showed that mobile genetic element-mediated tetracycline resistance is widespread in <italic>H. ovis</italic>, and that there is evidence of co-occurring virulence factors across clades suggesting convergent gene loss in the species. Finally, we introduced a novel <italic>Helcococcus</italic> species closely related to <italic>H. ovis</italic>, called <italic>H. bovis</italic> sp. nov., which has been reported to cause infection in humans.</p>