title: Conjugative transferability of the A/C plasmids from Salmonella enterica isolates that possess or lack bla(CMY) in the A/C plasmid backbone.
abstract: The objective of this study was to understand the conjugative transmissibility of resistance plasmids present in 205 Salmonella enterica isolates from bovine sources. Polymerase chain reaction (PCR)-based replicon typing was used to type plasmid replicons. Conjugation experiments were preformed in triplicate at 30 degrees C and 37 degrees C on solid medium. PCR mapping of the A/C transfer gene operon was done on 17 Salmonella Newport isolates that were only positive for A/C. Eighty-six percent (n = 177) of the Salmonella isolates were multidrug resistant (MDR) with resistance to 3-12 antimicrobial agents. Of these, 82% (n = 146) were resistant to extended-spectrum cephalosporins and possessed a bla(CMY) gene. A/C was the predominant replicon detected, present in 90% (n = 160) of the MDR isolates. Twenty-three percent (n = 37) of the A/C-positive strains were positive for a second replicon. Replicons coresident with A/C included I1, N, B/O, HI1, and HI2. Only 31% (n = 54) of the MDR isolates produced transconjugants, and most of these donors carried multiple replicons. A/C cotransferred with B/O, N, and I1 at both 30 degrees C and 37 degrees C and with HI2 at 30 degrees C. Seven Salmonella Newport isolates that produced transconjugants possessed only the single A/C replicon and lacked bla(CMY). PCR mapping of the A/C transfer gene operon in ten Salmonella Newport isolates that carried bla(CMY) revealed a bla(CMY) inverted repeat element integrated between the traA and traC genes. These results suggest that A/C may have been a conjugative plasmid before the integration of bla(CMY) into the transfer gene operon. Additionally, transfer deficient A/C replicons may be mobilized in the presence of certain compatible conjugative plasmids.
authors.affiliation: Southern Plains Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, College Station, Texas 77845, USA. toni.poole@ars.usda.gov
authors.forename: Toni L
authors.initials: TL
authors.lastname: Poole
authors.forename: Tom S
authors.initials: TS
authors.lastname: Edrington
authors.forename: Dayna M
authors.initials: DM
authors.lastname: Brichta-Harhay
authors.forename: Alessandra
authors.initials: A
authors.lastname: Carattoli
authors.forename: Robin Carl
authors.initials: RC
authors.lastname: Anderson
authors.forename: David J
authors.initials: DJ
authors.lastname: Nisbet
mesh_terms: D000818:Animals; D002417:Cattle; D003227:Conjugation, Genetic; D004926:Escherichia coli / Q000235:genetics; D005243:Feces / Q000382:microbiology; D005260:Female; D022761:Gene Transfer, Horizontal; D019450:Genes, MDR; D005838:Genotype; D008297:Male; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D010957:Plasmids / Q000737:chemistry / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012093:Replicon / Q000235:genetics; D019779:Salmonella enterica / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D012867:Skin / Q000382:microbiology; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D001618:beta-Lactamases