title: Prevalence and antimicrobial resistance profiles of Escherichia coil O157:H7 and Salmonella isolated from feedlot lambs.
abstract: The present study examined the incidence of Escherichia coli O:H7 and Salmonella in feedlot lambs. Fifty-six feedlot lambs from eight sheep farming operations were grouped in a single drylot pen, fed, and managed as is typical in the southwestern United States. Fecal samples were collected on days 0, 46, 87, and 122 of the feeding period via rectal palpation. Wool samples (ventral midline) were collected one time only at the feedlot, immediately prior to shipping to the processing plant, and carcass swabs were collected following slaughter. All samples were cultured for E. coli O157:H7, Salmonella, and fecal coliforms, and select isolates were examined for antimicrobial susceptibility. Overall, the percentages of fecal and wool samples positive for E. coli O157:H7 averaged 9 and 18%, respectively. One carcass swab was E. coli O157:H7 positive. Of the 155 fecal samples collected, 11 (7%) were Salmonella positive. Salmonella was detected in nearly 50% of the wool samples collected prior to slaughter, while none of the carcasses were Salmonella positive 24 h postslaughter. All isolates (E. coli O157:H7, Salmonella, and fecal coliforms) were susceptible to ceftiofur, enrofloxacin, and trimethoprim-sulfamethoxazole. One E. coli O157:H7 isolate cultured from a carcass swab was resistant to seven antibiotics, and seven wool E. coli O157:H7 isolates were multidrug resistant. Results of this research demonstrate that feedlot sheep are naturally colonized with E. coli O157:H7 and Salmonella and wool can be a source of carcass contamination; however, in-plant processing procedures and intervention strategies were largely effective in preventing carcass contamination.
authors.affiliation: Food and Feed Safety Research Unit, Southern Plains Agricultural Research Center, U.S. Department of Agriculture, Agricultural Research Service, College Station, Texas 77845, USA. edrington@ffsru.tamu.edu
authors.forename: Tom S
authors.initials: TS
authors.lastname: Edrington
authors.forename: Melissa
authors.initials: M
authors.lastname: Long
authors.forename: Tim T
authors.initials: TT
authors.lastname: Ross
authors.forename: Jack D
authors.initials: JD
authors.lastname: Thomas
authors.forename: Todd R
authors.initials: TR
authors.lastname: Callaway
authors.forename: Robin C
authors.initials: RC
authors.lastname: Anderson
authors.forename: Frank
authors.initials: F
authors.lastname: Craddock
authors.forename: Mike W
authors.initials: MW
authors.lastname: Salisbury
authors.forename: David J
authors.initials: DJ
authors.lastname: Nisbet
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015169:Colony Count, Microbial; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D019453:Escherichia coli O157 / Q000187:drug effects*; D005243:Feces / Q000382:microbiology; D005506:Food Contamination / Q000517:prevention & control; D008826:Microbial Sensitivity Tests; D015995:Prevalence; D012475:Salmonella / Q000187:drug effects* / Q000302:isolation & purification; D012756:Sheep / Q000382:microbiology*; D014935:Wool / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents