Diversity of Ochrobactrum species in food animals, antibiotic resistance phenotypes and polymorphisms in the bla OCH gene

Abstract

Twenty-six lactose non-fermenting, oxidase, urease and citrate positive Gram negative rods, isolated from broiler chickens, pigs and cattle at slaughter, were subjected to MALDI-TOF mass spectrometry and 16S rDNA sequencing for identification. Susceptibility to 14 antimicrobials was determined by the disc diffusion method. Ochrobactrum isolates resistant to third generation cephalosporins were PCR-screened for the presence of the O. anthropi ampC gene (bla_OCH). A 547 bp internal segment of bla_OCH in the Ochrobactrum species was amplified with a newly designed primer set and a phylogenetic reconstruction based on the complete amino acid sequence of bla_OCH obtained from 9 Ochrobactrum strains in our collection and 20 O. anthropi available in the GenBank was undertaken. All the Ochrobactrum isolates were resistant to the expanded-spectrum beta-lactams and streptomycin. None of the isolates was resistant to imipenem while 41.7% to 50.0% of them were resistant to fluoroquinolones. The bla_OCH gene was detected in 16 (66.7%) and 20 (83.3%) of the 24 Ochrobactrum isolates using primers designed for O. anthropi and the newly designed primer set, respectively. Six AmpC variants grouped into two divergent clusters were identified. This is the first report of the complete nucleotide sequence of the non-Ochrobactrum anthropi species bla_OCH gene.

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