A new OCH β-lactamase from a Brucella pseudintermedia (Ochrobactrum pseudintermedium) strain isolated from Zophobas morio larvae

Objectives: OCH class C β-lactamases have been reported in several species belonging to the Brucella genus that were formerly known as Ochrobactrum. Moreover, only one complete genome of Brucella pseudintermedia has been published. In this work, we describe the genome of a B. pseudintermedia strain possessing a new bla_OCH gene that was isolated from Zophobas morio larvae.

Methods: Hybrid whole-genome sequencing analysis (Illumina and Nanopore) was used to identify and characterise the strain (Ops-OCH-23). Phylogenetic analyses based on the 16S rRNA gene sequence and a core-genome alignment were performed to study the relationships among Ops-OCH-23 and deposited genomes. Moreover, all deposited bla_OCH genes were compared to the one found in Ops-OCH-23.

Results: Ops-OCH-23 showed a susceptibility profile consistent with the production of AmpC β-lactamase(s). Its genome consisted of two chromosomes, of which one carried the bla_OCH gene. Such gene encoded a new class C OCH β-lactamase among the fifteen so far reported. Two plasmids (120-Kb and 59-Kb) without any associated antimicrobial resistance genes were also found. Analysis of 16S rRNA revealed that Ops-OCH-23 shared 100% homology with four deposited B. pseudintermedia strains. Moreover, the core-genome analysis indicated that the closest match (279 ΔSNVs) to Ops-OCH-23 was strain CTOTU49018 isolated from an urban environment in Germany in 2013.

Conclusion: We described the second complete genome of a B. pseudintermedia that also encoded a new OCH β-lactamase variant. Overall, this report expands our knowledge regarding this rarely isolated Brucella species that have been reported so far only a few times in human sources.