Characterization of antimicrobial resistance in Salmonella enterica food and animal isolates from Colombia: identification of a qnrB19-mediated quinolone resistance marker in two novel serovars

M, Karczmarczyk , M, Martins, M, McCusker , S, Mattar , Leonard Amaral, N, Leonard , FM, Aarestrup , S Fanning

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Ninety-three Salmonella isolates recovered from commercial foods and exotic animals in Colombia were studied. The serotypes, resistance profiles and where applicable the quinolone resistance genes were determined. Salmonella Anatum (n=14), Uganda (19), Braenderup (10) and Newport (10) were the most prevalent serovars, and resistance to tetracycline (18.3%), ampicillin (17.2%) and nalidixic acid (14%) was most common. Nalidixic acid-resistant isolates displayed minimum inhibitory concentrations ranging from 32 to 1024 mu g mL-1. A Thr57 -> Ser substitution in ParC was the most frequent (12 of the 13 isolates). Six isolates possessed an Asp87 -> Tyr substitution in GyrA. No alterations in GyrA in a further seven nalidixic acid-resistant isolates were observed. Of these, four serovars including two Uganda, one Infantis and a serovar designated 6,7:d:-, all carried qnrB19 genes associated with 2.7 kb plasmids, two of which were completely sequenced. These exhibited 97% (serovar 6,7:d:- isolate) and 100% (serovar Infantis isolate) nucleotide sequence identity with previously identified ColE-like plasmids. This study demonstrates the occurrence of the qnrB19 gene associated with small ColE plasmids hitherto unrecognized in various Salmonella serovars in Colombia. We also report unusual high-level quinolone resistance in the absence of any DNA gyrase mutations in serovars S. Carrau, Muenchen and Uganda.
Original languageUnknown
Pages (from-to)10-19
JournalFEMS Microbiology Letters
Issue number1
Publication statusPublished - 1 Jan 2010

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