Transportation of cattle from the feedlot to the slaughter plant could influence hide contamination of Escherichia coli O157. A study was initiated to investigate the influence of transportation and lairage on shedding and hide contamination of E. coli O157. Fecal and hide samples were obtained from 40 pens of harvest-ready beef cattle at the feedlot prior to transport and again at the slaughter plant immediately after slaughter. Potential risk factors for hide contamination at the feedlot, during transport, and at slaughter were evaluated. A multilevel Poisson regression model was used to evaluate if transportation and lairage were associated with hide contamination by E. coli O157 in finished beef cattle. Lots of cattle held in E. coli O157-positive lairage pens had eight times greater risk of having positive slaughter hide samples compared with cattle held in culture-negative pens (relative risk, 8.0; 95% confidence interval, 1.6 to 38.8). Lots of cattle that were held in lairage pens contaminated with feces had three times greater risk for positive slaughter hide samples compared with cattle held in clean pens (relative risk, 3.1; 95% confidence interval, 1.2 to 7.9). Lots of cattle that were transported for long distances (> 160.9 km) had twice the risk of having positive hide samples at slaughter compared with cattle transported a shorter distance (relative risk, 2.4; 95% confidence interval, 1.1 to 5.1). These findings suggest that transportation and lairage should be considered in E. coli O157 control strategies.

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.

Transportation of cattle to the slaughter plant could influence hide contamination with Salmonella enterica. Fecal and hide samples were obtained from 40 lots of cattle at the feedlot and again at the slaughter plant. Potential risk factors for hide contamination were evaluated. A multilevel Poisson regression model was used to determine whether transportation and lairage were associated with hide contamination by Salmonella. Cattle with hide samples positive for Salmonella at the feedlot had twice the risk of having positive slaughter hide samples compared with cattle without positive feedlot hide samples (relative risk [RR], 1.9). Cattle transported in trailers from which samples positive for Salmonella were collected had twice the risk of having positive slaughter hide samples compared with cattle transported in culture-negative trailers (RR, 2.3). Cattle transported for long distances had twice the risk of having positive hide samples at slaughter compared with cattle transported shorter distances (RR, 2.3). Cattle held in lairage pens contaminated with feces had twice the risk of having positive slaughter hide samples compared with cattle held in clean pens (RR, 1.8). Cattle held off feed longer than 18 h before loading had twice the risk of having positive slaughter hide samples compared with cattle held off feed for shorter times (RR, 1.7). Cattle that were agitated during loading had twice the risk of having positive slaughter hide samples compared with cattle that were calm (RR, 2.2). These findings suggest that variables associated with transportation and lairage can impact the presence of Salmonella on the hides of cattle at slaughter.

Although dry/semidry fermented sausages are characterized as being of low-to-moderate risk for human listeriosis on a per-serving and per-annum basis, data are lacking relative to the fate of postprocessing Listeria monocytogenes contamination during storage of such products. This study evaluated the effect of inoculum preparation and storage conditions on the fate of L. monocytogenes on vacuum-packaged salami. Commercially produced salami was sliced and inoculated (4 +/- 1.3 log CFU/ cm2) with one of four types of inocula. All inocula consisted of the same 10-strain L. monocytogenes composite, cultivated as individual strains prior to mixing for inoculation. Active cultures of individual strains were prepared (30 degrees C, 24 h) in either tryptic soy broth (containing 0.25% glucose) plus 0.6% yeast extract (TSBYE), tryptic soy broth without glucose plus 0.6% yeast extract (TSBYE-G), TSBYE-G plus 1% glucose (TSBYE+G), or in TSBYE, and then habituated (7 degrees C, 72 h) in sterile salami homogenate (10% [wt/wt] with distilled water). Inoculated salami slices were vacuum packaged, stored at 4, 12, or 25 degrees C, and analyzed (three samples per treatment in each of two replicates) periodically for surviving bacterial counts. In general, pathogen levels decreased during storage and reached levels below the detection limit (-0.4 log CFU/cm2) between 27 and 90 days of storage, depending on temperature of storage and inoculum type. Death rates (log CFU/cm2/day) were found to increase as storage temperature increased, with the exception of the acid-adapted (TSBYE+G) cells, which decreased more rapidly at 4 degrees C than at 12 or 25 degrees C. The habituated inoculum was inactivated at a faster rate than other inocula at 12 and 25 degrees C, but performed similarly to nonadapted (TSBYE-G) and partially acid-adapted (TSBYE) inocula at 4 degrees C. These data may be used to supplement existing information for use in future risk assessments.

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This study evaluated the fate of inoculated Listeria monocytogenes on frankfurters stored under conditions simulating those that may be encountered between manufacturing and consumption. Frankfurters with or without 1.5% potassium lactate and 0.1% sodium diacetate (PL/SD) were inoculated (1.8 +/- 0.1 log CFU/cm(2)) with a 10-strain composite of L. monocytogenes, vacuum-packaged, and stored under conditions simulating predistribution storage (24 h, 4 degrees C), temperature abuse during transportation (7 h, 7 degrees C followed by 7 h, 12 degrees C), and storage before purchase (60 d, 4 degrees C; SBP). At 0, 20, 40, and 60 d of SBP, samples were exposed to conditions simulating delivery from stores to homes or food establishments (3 h, 23 degrees C), and then opened or held vacuum-packaged at 4 or 7 degrees C for 14 d (SHF). Pathogen counts remained relatively constant on frankfurters with PL/SD regardless of product age and storage conditions; however, they increased on product without antimicrobials. In vacuum-packaged samples, during SHF at 4 degrees C, the pathogen grew faster (P < 0.05) on older product (20 d of SBP) compared to product that was fresh (0 d of SBP); a similar trend was observed in opened packages. At 7 degrees C, the fastest growth (0.35 +/- 0.02 log CFU/cm(2)/d) was observed on fresh product in opened packages; in vacuum-packages, growth rates on fresh and aged products were similar. By day 40 of SBP the pathogen reached high numbers and increased slowly or remained unchanged during SHF. This information may be valuable in L. monocytogenes risk assessments and in development of guidelines for storage of frankfurters between package opening and product consumption.