Identification of a multidrug resistance genomic island harboring a nonfunctional optrA gene in Campylobacter coli of chicken origin.

Campylobacter spp., such as Campylobacter jejuni and Campylobacter coli , are important zoonotic Gram-negative pathogens that cause acute intestinal diseases in humans. In this study, a retrospective analysis was conducted on previously collected Campylobacter isolates from antimicrobial resistance surveillance. A total of 29 optrA -positive C. coli strains were identified and subjected to second-generation sequencing. Multilocus sequence typing and single nucleotide polymorphism analyses demonstrated that the 29 optrA -positive isolates were genetically homogeneous. Notably, among the 29 isolated strains, the Δ optrA variants exhibit a nonsense mutation at position 979 where the base C is substituted by T, leading to the formation of a premature termination codon. The alignment of sequences and genetic environmental characteristics suggested that Δ optrA located on a chromosomally carried multidrug-resistant genomic island. There are other resistant genes on the multidrug resistance genomic island, such as aph(2'')-If , aph(3′)-III , aadE , tet (O), tet (L), cat , erm (A), optrA and bla OXA-61. As a result, the 29 Δ optrA -positive strains displayed susceptibility to both florfenicol and linezolid. The Δ optrA gene is linked to the erm (A) gene, resulting in the formation of translocatable unit (TU) that are encompassed by two copies of IS 1216 mobile elements. Multiple occurrences of similar TUs have been documented in numerous C. coli and provided evidence for the significance of TUs in facilitating the transfer of drug resistance genes in C. coli. • The Δ optrA gene is located on the MDRGI of C. coli. • All the Δ optrA -positive C. coli strains belonged to ST872. • One transposition unit was formed through the involvement of the IS 1216 element. • C. coli integrates various resistance genes, leading to the formation of MDRGI. [ABSTRACT FROM AUTHOR]