Antimicrobial resistance in nontyphoidal Salmonella from food sources in Colombia: Evidence for an unusual plasmid-localized class 1 integron in serotypes typhimurium and anatum

Rebecca O'Mahony, Teresa Quinn, Denise Drudy, Ciara Walsh, Paul Whyte, Salim Mattar, Séamus Fanning

Research output: Contribution to journalArticlepeer-review

Abstract

Seventy-two isolates representing 18 serotypes recovered from various food samples collected in Colombia were tested for antimicrobial susceptibilities. The collection was further characterized for extended-spectrum cephalosporin, aminoglycoside, and tetracycline resistance markers. Multidrug resistant (MDR) isolates were further investigated for class 1 integrons and were evaluated for the presence of conjugative plasmids along with a determination of the incompatibility group by polymerase chain reaction (PCR). Antibiogram analysis showed that the incidence rate of ceftiofur resistance was moderately high (15%). A similar level of resistance to neomycin and oxytetracycline (11% and 10%, respectively) was also observed. There was a high prevalence of gene cassettes as part of one or more class 1 integrons (61%), many of which contained determinants that contributed to the resistance profile. Class 1 integrons identified in MDR Salmonella enterica serotypes Typhimurium and Anatum isolates were characterized. Sequencing identified several incomplete open reading frames (ORFs) as part of a gene cassette (bla-imp-13, dfr7, blr1088, and aac8) along with a complete gene cassette (bla-oxa2) in each case. A mosaic of gene cassettes was identical in the two Salmonella serotypes. These integrons were located to a conjugative replicon. Plasmid profiling and incompatibility typing identified three plasmids belonging to Inc groups A/C, P, and W. Our study highlights the role of integrons, contributing to a MDR phenotype that is capable of dissemination to other bacteria.

Original languageEnglish
Pages (from-to)269-277
Number of pages9
JournalMicrobial Drug Resistance
Volume12
Issue number4
DOIs
Publication statusPublished - Dec 2006
Externally publishedYes

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