Characterization of Canadian cefoxitin-resistant non-typhoidal Salmonella isolates, 2005-06.
OBJECTIVE
Resistance to extended-spectrum cephalosporins has increased in Salmonella worldwide, and is a concern in both hospital and community settings. The aim of this report was to investigate cefoxitin-resistant Salmonella isolates identified from human clinical cases across Canada.


METHODS
Cefoxitin-resistant isolates, defined as having an MIC > or = 32 mg/L, were screened for the ampC classes DHA, FOX, ENT and CIT in a multiplex PCR followed by sequence analysis. Plasmid analysis by restriction fragment length polymorphism (RFLP) and replicon typing was performed on a convenience sample of cefoxitin-resistant Salmonella.


RESULTS
In 2005, 5.3% (181/3442) and in 2006, 3.1% (102/3250) of Salmonella isolates collected from all provinces across Canada displayed cefoxitin resistance. Seventy-one out of 283 (25.1%) were multidrug resistant (MDR), as defined by resistance to at least three different antibiotic classes. The bla(CMY-2) gene was harboured by 96.8% (274/283) of the cefoxitin-resistant isolates. Analysis of CMY-2 plasmids revealed that 19.7% contained genes conferring resistance to multiple antimicrobials. Replicon typing of transformant CMY-2 plasmid DNA revealed the predominance of I1-Igamma and A/C. Of the MDR CMY-2 plasmids, 75% contained replicon type A/C. RFLP patterns of CMY-2 plasmids revealed clusters corresponding to the I1-Igamma and A/C replicon types.


CONCLUSIONS
Incompatibility group I1-Igamma is the most prevalent of the Salmonella CMY-2 plasmids, while A/C is associated with MDR CMY-2 plasmids.
Mataseje
L F
LF
University of Manitoba, Winnipeg, Canada.
Xiao
J
J
Kost
S
S
Ng
L-K
LK
Doré
K
K
Mulvey
M R
MR
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002170:Canada; D002440:Cefoxitin / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D005260:Female; D005798:Genes, Bacterial; D005838:Genotype; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D010957:Plasmids / Q000032:analysis / Q000145:classification; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012093:Replicon; D012475:Salmonella / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification; D012480:Salmonella Infections / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D055815:Young Adult
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D002440:Cefoxitin