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Prevalence of Escherichia Coli O157 and Other Shiga-Toxin-Producing E. Coli in Lambs at Slaughter

1999; SAGE Publishing; Volume: 11; Issue: 6 Linguagem: Inglês

10.1177/104063879901100619

1943-4936

Brian J. McCluskey, Daniel H. Rice, Dale D. Hancock, Carolyn J. Hovde, Thomas E. Besser, Steacy Gray, Roger P. Johnson,

Viral gastroenteritis research and epidemiology

Ground beef has been implicated in most outbreaks of Shiga-toxin-producing Escherichia coli O157 infections in humans.1–3 No outbreaks of infection with this organism have been linked to lamb; however, ruminants such as sheep may contribute to transmission of this organism to humans. Shiga-toxin-producing E. coli (STEC) have been reported to be more prevalent in sheep and goats than in cattle and have been isolated from several retail meats, including lamb.4,5 Sheep can be colonized by E. coli O157 experimentally and through natural exposure, and this serotype has been isolated from retail lamb in the United States.6–8 Here, we describe a pilot study conducted to determine the prevalence of E. coli O157 and other STEC serotypes in market lambs just prior to slaughter and to evaluate specific factors that may be associated with a higher or lower prevalence of E. coli O157 in lambs at slaughter. Lambs were sampled at a slaughter facility that processed lambs only located in the midwestern United States. All samples were collected over 3 days in October 1995. Sixty lambs were sampled from lots that exceeded 100 lambs; otherwise, 30 lambs were sampled per lot. Each lot was categorized by source (single farm flock vs. commercial feedlot), distance shipped, and elapsed time from farm to slaughter. Fecal samples were collected by rectal extraction of fecal pellets or, if feces were not in pellet form, by rectal swab with a cotton-tipped swab. For detection of E. coli O157, a single fecal pellet or fecal swab was placed in a culture tube containing 3 ml of tryptic soy brotha to which had been added 40 mg/ml vancomycinb and 50 ng/ml cefiximec (TSBcv). From every 10 lamb in order of sampling, a larger volume of feces was obtained with a gloved hand for culture of 10 g of feces (in addition to the pellet or swab cultures on the same lambs). The larger samples were placed into a polypropylene tube containing 20 ml of TSBcv to which was also added 2.5 mg/ml potassium tellurited (TSBcvt). From each of the same systematically selected lambs, a single fecal pellet was placed into a culture tube containing 10 ml of EC broth containing 20 mg/ml of novobiocind (ECBn). Samples in ECBn were used to determine the presence of STEC