title: Molecular Characterization of Salmonella enterica Serovars Isolated from a Turkey Production Facility in the Absence of Selective Antimicrobial Pressure.
abstract: This study evaluated antimicrobial resistance and virulence factors in Salmonella enterica isolated from a turkey flock in which the birds were raised in an environment where antimicrobials were not administered to the birds, either through feed or water. Salmonella was isolated from turkeys and various environmental samples in the facility using conventional microbiological procedures. Isolates were serotyped and analyzed phenotypically by antimicrobial resistance profiling and genotypically by pulsed-field gel electrophoresis (PFGE) fingerprinting, integron analysis, plasmid profiling, replicon-based incompatibility (Inc) group typing, and virulence gene profiling. Ninety-five S. enterica isolates were isolated from cecal contents (n = 29), feed (n = 22), leftover feed (n = 13), litter (n = 12), drinkers (n = 10), environment (n = 8), and an insect. The following serotypes were identified: Montevideo (24%), Anatum (22%), Agona (17%), Kentucky and Worthington (12%), Senftenberg (11%), and rough phenotypes (3%). The majority of isolates (61/95; 64%) were susceptible to 12 antimicrobials tested; however, despite the absence of antimicrobials in the facility, approximately 36% of the isolates were resistant to two to five antimicrobials. Class 1 integrons were detected in 8% of the isolates. The integron sequence analysis revealed dihydrofolate reductase (dhfr) and aminoglycoside adenylyl transferase (aadA2) genes, which encode trimethoprim and streptomycin resistance, respectively. Furthermore, 71% of the isolates had at least one plasmid. There were five plasmid replicon types identified among the isolates, including IncI1, IncHI2, IncFIIA, IncB/O, and IncP, with variable prevalence among the serotypes. All 95 isolates tested polymerase chain reaction-positive for 19 virulence genes and negative for virD4 and virB4. The virulence gene profiles were similar within the isolates from the same serotype. Within particular serotypes, PFGE patterns revealed 100% similarity, even when the bacterial strains were isolated from different sources, indicating cross-colonization of sources within the turkey facility. On this antibiotic-free turkey farm, turkeys and feed appeared to be the major reservoirs of multidrug-resistant Salmonella, which harbored multiple virulence genes.
authors.affiliation: 1 Division of Microbiology, National Center for Toxicological Research , U.S. Food and Drug Administration, Jefferson, Arkansas.
authors.forename: Yasser M
authors.initials: YM
authors.lastname: Sanad
authors.affiliation: 1 Division of Microbiology, National Center for Toxicological Research , U.S. Food and Drug Administration, Jefferson, Arkansas.
authors.forename: Kelly
authors.initials: K
authors.lastname: Johnson
authors.affiliation: 2 Center for Food Safety and Department of Food Science, University of Arkansas , Fayetteville, Arkansas.
authors.forename: Si Hong
authors.initials: SH
authors.lastname: Park
authors.affiliation: 1 Division of Microbiology, National Center for Toxicological Research , U.S. Food and Drug Administration, Jefferson, Arkansas.
authors.forename: Jing
authors.initials: J
authors.lastname: Han
authors.affiliation: 1 Division of Microbiology, National Center for Toxicological Research , U.S. Food and Drug Administration, Jefferson, Arkansas.
authors.forename: Joanna
authors.initials: J
authors.lastname: Deck
authors.affiliation: 1 Division of Microbiology, National Center for Toxicological Research , U.S. Food and Drug Administration, Jefferson, Arkansas.
authors.forename: Steven L
authors.initials: SL
authors.lastname: Foley
authors.affiliation: 3 Department of Animal and Nutritional Science, West Virginia University , Morgantown, West Virginia.
authors.forename: Brett
authors.initials: B
authors.lastname: Kenney
authors.affiliation: 2 Center for Food Safety and Department of Food Science, University of Arkansas , Fayetteville, Arkansas.
authors.forename: Steven
authors.initials: S
authors.lastname: Ricke
authors.affiliation: 1 Division of Microbiology, National Center for Toxicological Research , U.S. Food and Drug Administration, Jefferson, Arkansas.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Nayak
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000276:immunology; D002432:Cecum / Q000382:microbiology; D004269:DNA, Bacterial / Q000302:isolation & purification; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004777:Environment; D005516:Food Microbiology; D005525:Food-Processing Industry; D005838:Genotype; D032023:Integrons / Q000235:genetics; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics; D012093:Replicon / Q000235:genetics; D019779:Salmonella enterica / Q000235:genetics* / Q000302:isolation & purification; D065288:Serogroup; D014422:Turkeys / Q000382:microbiology*; D037521:Virulence Factors
chemical_list: D000890:Anti-Infective Agents; D004269:DNA, Bacterial; D037521:Virulence Factors