Description of sp. nov., carrying a novel class C β-lactamase gene variant, isolated from gut samples of Atlantic mackerel ().

Three β-lactam resistant bacterial strains isolated from gut samples of wild Atlantic mackerel () collected from the northern North Sea were characterized by polyphasic analyses. The strains were determined to belong to the genus but could not be assigned to a known species. The nearly-complete 16S rRNA gene sequence showed the highest similarity (99.9%) to four different species, although partial sequence exhibited relatively low similarities to (93.4%) and other spp. Genome sequencing and subsequent digital DNA-DNA hybridization (dDDH), average nucleotide identity (ANI) analysis and core genome analysis confirmed that these strains represent a novel species within the genus . The three strains demonstrated ANIb values >99.5% with each other, confirming that all three strains (CCUG 74779 = CECT 30571, CCUG 74780 and CCUG 74781) belong to the same genomospecies. Phylogenomic analysis confirmed that the strains form a distinct genomic clade, representing a novel taxonomic species, for which the name sp. nov., is proposed, with strain CCUG 74779 (=CECT 30571) designated as the type strain. We report the complete genome sequence of the type strain of sp. nov. and show that it carries a gene encoding a novel variant of a chromosomally-encoded class C β-lactamase, which has been designated as PFL-7.