RESUMEN
This study was conducted to identify the origin of Escherichia coli O157:H7 contamination on steer hides at the time of harvest. Samples were collected from the feedlot, transport trailers, and packing plant holding pens and from the colons and hides of feedlot steers. A total of 50 hide samples were positive for E. coli O157:H7 in two geographical locations: the Midwest (25 positive hides) and Southwest (25 positive hides). Hide samples were screened, and the presence of E. coli O157: H7 was confirmed. E. coli O157:H7 isolates were fingerprinted by pulsed-field gel electrophoresis and subjected to multiplex PCR procedures for amplification of E. coli O157:H7 genes stx1, stx2, eaeA, fliC, rfbEO157, and hlyA. Feedlot water trough, pen floor, feed bunk, loading chute, truck trailer side wall and floor, packing plant holding pen floor and side rail, and packing plant cattle drinking water samples were positive for E. coli O157:H7. Pulsed-field gel electrophoresis banding patterns were analyzed after classifying isolates according to the marker genes present and according to packing plant. In this study, hide samples positive for E. coli O157:H7 were traced to other E. coli O157:H7-positive hide, colon, feedlot pen floor fecal, packing plant holding pen drinking water, and transport trailer side wall samples. Links were found between packing plant side rails, feedlot loading chutes, and feedlot pens and between truck trailer, different feedlots, and colons of multiple cattle. This study is the first in which genotypic matches have been made between E. coli O157:H7 isolates obtained from transport trailer side walls and those from cattle hide samples within the packing plant.
Asunto(s)
Crianza de Animales Domésticos/normas , Enfermedades de los Bovinos/microbiología , ADN Bacteriano/análisis , Infecciones por Escherichia coli/veterinaria , Escherichia coli O157/aislamiento & purificación , Piel/microbiología , Animales , Técnicas de Tipificación Bacteriana , Bovinos , Enfermedades de los Bovinos/epidemiología , Recuento de Colonia Microbiana , Electroforesis en Gel de Campo Pulsado , Microbiología Ambiental , Infecciones por Escherichia coli/epidemiología , Infecciones por Escherichia coli/microbiología , Escherichia coli O157/genética , Pisos y Cubiertas de Piso , Contaminación de Alimentos , Microbiología de Alimentos , Amplificación de Genes , Cabello/microbiología , Vivienda para Animales , Masculino , Reacción en Cadena de la PolimerasaRESUMEN
A multilaboratory study was conducted to compare the automated BAX system and the standard cultural methods for detection of Listeria monocytogenes in foods. Six food types (frankfurters, soft cheese, smoked salmon, raw, ground beef, fresh radishes, and frozen peas) were analyzed by each method. For each food type, 3 inoculation levels were tested: high (average of 2 CFU/g), low (average of 0.2 CFU/g) and uninoculated controls. A total of 25 laboratories representing government and industry participated. Of the 2335 samples analyzed, 1109 were positive by the BAX system and 1115 were positive by the standard method. A Chi square analysis of each of the 6 food types, at the 3 inoculation levels tested, was performed. For all foods, except radishes, the BAX system performed as well as or better than the standard reference methods based on the Chi square results.