Genotypic Analyses of
            <i>Escherichia coli</i>
            O157:H7 and O157 Nonmotile Isolates Recovered from Beef Cattle and Carcasses at Processing Plants in the Midwestern States of the United States

Rivera-Betancourt

et al. 2003

Self Cite

401

305

The seasonal prevalence of Escherichia coli O157:H7, Salmonella, non-O157 E. coli (STEC), and stx-harboring cells was monitored at three Midwestern fed-beef processing plants. Overall, E. coli O157:H7 was recovered from 5.9% of fecal samples, 60.6% of hide samples, and 26.7% of carcasses sampled before the preevisceration wash. This pathogen also was recovered from 1.2% (15 of 1,232) of carcasses sampled at chilling (postintervention) at approximate levels of ,3.0 cells per 100 cm 2 . In one case, the E. coli O157:H7 concentration dropped from ca. 1,100 cells per 320 cm 2 at the preevisceration stage to a level that was undetectable on ca. 2,500 cm 2 at the postintervention stage. The prevalence of E. coli O157:H7 in feces peaked in the summer, whereas its prevalence on hide was high from the spring through the fall. Overall, Salmonella was recovered from 4.4, 71.0, and 12.7% of fecal, hide, and preevisceration carcass samples, respectively. Salmonella was recovered from one postintervention carcass (of 1,016 sampled). Salmonella prevalence peaked in feces in the summer and was highest on hide and preevisceration carcasses in the summer and the fall. Non-O157 STEC prevalence also appeared to vary by season, but the ef ciency in the recovery of isolates from stx-positive samples ranged from 37.5 to 83.8% and could have in uenced these results. Cells harboring stx genes were detected by PCR in 34.3, 92.0, 96.6, and 16.2% of fecal, hide, preevisceration carcass, and postintervention carcass samples, respectively. The approximate level of non-O157 STEC and stx-harboring cells on postintervention carcasses was $3.0 cells per 100 cm 2 for only 8 of 199 carcasses (4.0%). Overall, the prevalence of E. coli O157:H7, Salmonella, and non-O157 STEC varied by season, was higher on hides than in feces, and decreased dramatically, along with pathogen levels, during processing and during the application of antimicrobial interventions. These results demonstrate the effectiveness of the current interventions used by the industry and highlight the signi cance of hides as a major source of pathogens on beef carcasses.

Section: Discussionmentioning

confidence: 99%

Seasonal Prevalence of Shiga Toxin–Producing Escherichia coli, Including O157:H7 and Non-O157 Serotypes, and Salmonella in Commercial Beef Processing Plants

Barkocy-Gallagher

Rivera-Betancourt

et al. 2003

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401

305

“…When contamination exceeds this limit, the interventions will be overwhelmed and carcass contamination will not be eliminated. The incoming E. coli O157:H7 contamination of most concern is that found on the hides of cattle entering the processing facility (4,5,7,20). Recently, postharvest interventions have been focused on the hide in an attempt to keep contamination levels from overwhelming downstream antimicrobial interventions applied to the carcass (7)(8)(9).…”

Section: Discussionmentioning

confidence: 99%

“…Samples were processed according to methods previously described with slight modifications (5,6). Carcass, hide, and truck sponge samples were enriched with 80 ml of TSB after the 250-l aliquot for enumeration was removed.…”

Section: Animalsmentioning

confidence: 99%

Transportation and Lairage Environment Effects on Prevalence, Numbers, and Diversity of Escherichia coli O157:H7 on Hides and Carcasses of Beef Cattle at Processing

Bosilevac

Brichta-Harhay

et al. 2007

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124

Hide has been established as the main source of carcass contamination during cattle processing; therefore, it is crucial to minimize the amount of Escherichia coli O157:H7 on cattle hides before slaughter. Several potential sources of E. coli O157: H7 are encountered during transportation and in the lairage environment at beef-processing facilities that could increase the prevalence and numbers of E. coli O157:H7 on the hides of cattle. On three separate occasions, samples were obtained from cattle at the feedlot and again after cattle were stunned and exsanguinated at the processing plant (286 total animals). The prevalence of E. coli O157:H7 on hides increased from 50.3 to 94.4% between the time cattle were loaded onto tractor-trailers at the feedlot and the time hides were removed in the processing plant. Before transport, nine animals had E. coli O157:H7 in high numbers (Ͼ0.4 CFU/cm 2 ) on their hides. When sampled at the slaughter facility, the number of animals with high hide numbers had increased to 70. Overall, only 29% of the E. coli O157:H7 isolates collected postharvest (221 of 764) matched pulsed-field gel electrophoresis types collected before transport. The results of this study indicate that transport to and lairage at processing plants can lead to increases in the prevalence and degree of E. coli O157:H7 contamination on hides and the number of E. coli O157:H7 pulsed-field gel electrophoresis types associated with the animals. More study is needed to confirm the mechanism by which additional E. coli O157:H7 strains contaminate cattle hides during transport and lairage and to design interventions to prevent this contamination.Recent work has revealed that the major source of beef carcass contamination is cattle hides (4,7,8,20). In a study done by , the carcass contamination rates during processing could not be accounted for by the fecal prevalence of Escherichia coli O157:H7, but could be accounted for by hide prevalence. Bosilevac et al. (7,8) and Nou et al. (20) extended these findings by demonstrating that antimicrobial interventions targeting cattle hides lead to drastic reductions in the rates of carcass contamination with E. coli O157:H7.Because hide is the main source of carcass contamination, it is crucial to minimize the amount of E. coli O157: H7 on cattle hides before slaughter. Cattle can shed E. coli O157:H7 in their feces at concentrations as high as 10 6 CFU/g (24). One such high shedder could contaminate the hides of many animals, especially in high-density situations like the transport truck or lairage environment. Few studies have addressed the effects of external contamination sources on E. coli O157:H7 hide prevalence during transport and lairage. Barham et al. (3) isolated E. coli O157:H7 from samples taken from truck trailers before cattle were loaded. It was not

“…Nou et al (23) demonstrated that hide dehairing, which in effect sanitizes the animal hide, can greatly reduce carcass bacterial loads and eliminate E. coli O157. Barkocy-Gallagher et al (3) showed that .66% of the E. coli O157:H7 isolates from beef carcasses identi ed late in processing could be tracked by pulsed-eld gel electrophoresis to the same carcass early in processing. This nding indicates that the E. coli O157 population associated with the animal or carcass persisted throughout processing.…”

Section: Enumeration Of Aerobic Bacteria and Enterobacteriaceaementioning

confidence: 99%

Escherichia coli O157 Prevalence and Enumeration of Aerobic Bacteria, Enterobacteriaceae, and Escherichia coli O157 at Various Steps in Commercial Beef Processing Plants

Bosilevac

Nou

et al. 2004

Self Cite

221

122

The effectiveness of current antimicrobial interventions used in reducing the prevalence or load of Escherichia coli O157 and indicator organisms on cattle hides and carcasses at two commercial beef processing plants was evaluated. Sponge sampling of beef cattle was performed at ve locations from the initial entry of the animals to the slaughter oor to the exit of carcasses from the ''hotbox'' cooler. For each sample, E. coli O157 prevalence was determined and total aerobic bacteria, Enterobacteriaceae, and E. coli O157 were enumerated. E. coli O157 was found on 76% of animal hides coming into the plants, but no carcasses leaving the cooler were identi ed as contaminated with E. coli O157. A positive relationship was seen between the incidence of E. coli O157 in hide samples and that in preevisceration samples. Aerobic plate counts and Enterobacteriaceae counts averaged 7.8 and 6.2 log CFU/100 cm 2 , respectively, on hides, and 1.4 and 0.4 log CFU/100 cm 2 , respectively, on chilled carcasses. Aerobic plate counts and Enterobacteriaceae counts on preevisceration carcasses were signi cantly related to the respective levels on the corresponding hides; the carcasses of animals whose hides carried higher numbers of bacteria were more likely to carry higher numbers of bacteria. Implementation of the sampling protocol described here would allow processors to evaluate the ef cacy of on-line antimicrobial interventions and allow industrywide benchmarking of hygienic practices.Escherichia coli O157:H7 has been a pathogen of concern to the meat processing industry for two decades. Cases of hemorrhagic colitis caused by E. coli O157:H7 were associated with consumption of undercooked ground beef in the early 1980s (26). In the United States during 1992 and 1993, an outbreak of E. coli O157:H7 infection associated with consumption of ground beef caused hundreds of illnesses and four deaths (31). These events led the Food Safety and Inspection Service (FSIS) to declare the E. coli O157:H7 organism an adulterant in ground beef and to require that meat processors establish hazard analysis and critical control point (HACCP) plans for their plants (12). Since this time, numerous intervention strategies focusing on prevention of carcass contamination and decontamination of carcasses have been designed, tested, and put into practice at commercial processing plants.Recent studies have demonstrated that combinations of antimicrobial interventions are more effective at reducing * Author for correspondence. Tel: 402-762-4227; Fax: 402-762-4149; E-mail: arthur@email.marc.usda.gov. † Names are necessary to report factually on available data; however, the U.S. Department of Agriculture neither guarantees nor warrants the standard of the product, and the use of the name by the U.S. Department of Agriculture implies no approval of the product to the exclusion of others that may also be suitable. ‡ Present address: Room 119, Veterinary Diagnostic Center, East Campus, University of Nebraska, Lincoln, NE 68583-0907, USA.surface contami...