title: Characterization of extended-spectrum cephalosporin-resistant Salmonella enterica serovar Heidelberg isolated from food animals, retail meat, and humans in the United States 2009.
abstract: Salmonella enterica is one of the most common causes of foodborne illness in the United States. Although salmonellosis is usually self-limiting, severe infections typically require antimicrobial treatment, and ceftriaxone, an extended-spectrum cephalosporin (ESC), is commonly used in both adults and children. Surveillance conducted by the National Antimicrobial Resistance Monitoring System (NARMS) has shown a recent increase in ESC resistance among Salmonella Heidelberg isolated from food animals at slaughter, retail meat, and humans. ESC resistance among Salmonella in the United States is usually mediated by a plasmid-encoded bla(CMY) β-lactamase. In 2009, we identified 47 ESC-resistant bla(CMY)-positive Heidelberg isolates from humans (n=18), food animals at slaughter (n=16), and retail meats (n=13) associated with a spike in the prevalence of this serovar. Almost 90% (26/29) of the animal and meat isolates were isolated from chicken carcasses or retail chicken meat. We screened NARMS isolates for the presence of bla(CMY), determined whether the gene was plasmid-encoded, examined pulsed-field gel electrophoresis patterns to assess the genetic diversities of the isolates, and categorized the bla(CMY) plasmids by plasmid incompatibility groups and plasmid multi-locus sequence typing (pMLST). All 47 bla(CMY) genes were found to be plasmid encoded. Incompatibility/replicon typing demonstrated that 41 were IncI1 plasmids, 40 of which only conferred bla(CMY)-associated resistance. Six were IncA/C plasmids that carried additional resistance genes. pMLST of the IncI1-bla(CMY) plasmids showed that 27 (65.8%) were sequence type (ST) 12, the most common ST among bla(CMY)-IncI1 plasmids from Heidelberg isolated from humans. Ten plasmids had a new ST profile, ST66, a type very similar to ST12. This work showed that the 2009 increase in ESC resistance among Salmonella Heidelberg was caused mainly by the dissemination of bla(CMY) on IncI1 and IncA/C plasmids in a variety of genetic backgrounds, and is likely not the result of clonal expansion.
authors: Division of Foodborne, Waterborne, and Environmental Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30329, USA. gux8@cdc.gov
authors: J P
authors: JP
authors: Folster
authors: G
authors: G
authors: Pecic
authors: A
authors: A
authors: Singh
authors: B
authors: B
authors: Duval
authors: R
authors: R
authors: Rickert
authors: S
authors: S
authors: Ayers
authors: J
authors: J
authors: Abbott
authors: B
authors: B
authors: McGlinchey
authors: J
authors: J
authors: Bauer-Turpin
authors: J
authors: J
authors: Haro
authors: K
authors: K
authors: Hise
authors: S
authors: S
authors: Zhao
authors: P J
authors: PJ
authors: Fedorka-Cray
authors: J
authors: J
authors: Whichard
authors: P F
authors: PF
authors: McDermott
mesh_terms: D000328:Adult; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D018550:Cephalosporin Resistance / Q000235:genetics*; D002511:Cephalosporins / Q000494:pharmacology*; D002645:Chickens / Q000382:microbiology; D004269:DNA, Bacterial / Q000302:isolation & purification; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D014644:Genetic Variation; D006801:Humans; D008297:Male; D008460:Meat / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing / Q000379:methods; D010957:Plasmids; D012478:Salmonella Food Poisoning / Q000382:microbiology; D019779:Salmonella enterica / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D014481:United States; D001618:beta-Lactamases / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D004269:DNA, Bacterial; D001618:beta-Lactamases