Class 1 integrons in various Salmonella enterica serovars isolated from animals and identification of genomic island SGI1 in Salmonella enterica var. Meleagridis.
OBJECTIVE
To determine the prevalence of integron-mediated antibiotic resistance in a diverse sample set of Salmonella enterica isolated from animals.


METHODS
Multiplex PCR was used to detect class 1 integron gene sequences, and integron gene cassettes were identified by PCR mapping. Susceptibility to 18 antibiotics or antibiotic combinations commonly used in either human or veterinary medicine was measured using a microdilution method, and statistical comparisons of the frequency of resistance between groups were made using Fisher's two-sided probability test. Genotypic comparisons of isolates were made following pulsed-field gel electrophoresis of genomic DNA.


RESULTS
Thirty-two (30.8%) of 104 isolates contained class 1 integron sequences. Integron-positive isolates represented 15 different S. enterica serovars, were obtained from nine different animal species and had a higher frequency of non-integron-mediated antibiotic resistance (P < 0.05) compared with integron-negative isolates. One non-Typhimurium isolate (S. enterica Meleagridis) contained an SGI1 genomic island, including the antibiotic resistance gene cluster.


CONCLUSIONS
These data demonstrate that integron-mediated antibiotic resistance is common among diverse Salmonella serovars, many of them rare. In addition, SGI1 is not limited to Salmonella enterica Typhimurium DT104 or other commonly isolated serovars.
Ebner
Paul
P
Food Safety Center of Excellence, University of Tennessee, 2505 River Drive, Knoxville, TN 37996, USA. pebner@lsuhsc.edu
Garner
Kimberly
K
Mathew
Alan
A
D000818:Animals; D000829:Animals, Domestic; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005798:Genes, Bacterial / Q000235:genetics*; D032023:Integrons / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D005810:Multigene Family; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019779:Salmonella enterica / Q000187:drug effects / Q000235:genetics*
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial