Visual cleanliness scores of cattle at slaughter and microbial loads on the hides and the carcases.

In two abattoirs, visual cleanliness of 100 cattle was assessed before slaughter (on a scale of 1 to 4). From each animal, two sponge swabs (approximately 2000 cm(2) area, each) were taken: (a) from hide, immediately after sticking, and (b) from final carcase, but before chilling. In each swab sample, total viable count (TVC), Enterobacteriaceae count (EC) and the presence of Escherichia coli O157 were determined. The mean TVC/EC status of hides and final carcases differed significantly only between very dirty cattle (category 4) and all other less dirty or clean cattle (categories 1, 2 and 3), but not between the less dirty and clean cattle (between categories 1, 2 and 3). However, no clear relationship between the visual cleanliness of the hide and the occurrence of E coli O157 on hide or dressed carcases was observed. The study indicated the possibility that visual categorisation of cattle into only two main categories - one containing very dirty animals (category 4 in this work, corresponding to categories 4+5 in The UK Food Standards Agency system) and another containing all the other less dirty or clean animals (categories 1+2+3) - could be sufficient in practice.

Treatment of cattle hides with Shellac solution to reduce hide-to-beef microbial transfer.

The hide-to-beef microbial transfer-reducing effects of a novel Shellac treatment of hides (based on "on-hair immobilization" of microorganisms) were evaluated. In the hide-to-meat direct contact laboratory-based experiments, treatment of hides (of varying visual cleanliness) with Shellac produced significant microbial reductions on beef: up to 3.6 log(10) CFU/cm(2) of total viable count of bacteria (TVC), up to 2.5 log(10) CFU/cm(2) of Enterobacteriaceae (EC) and up to 1.7 log(10) CFU/cm(2) of generic Escherichia coli (GEC). In a small commercial abattoir under "bad-case" conditions (slaughtering dirty cattle, inadequate process hygiene), treatment of hides with Shellac produced significant microbial reductions on beef carcasses: 1.7 log(10) CFU/cm(2), 1.4 log(10) CFU/cm(2) and 1.3 log(10) CFU/cm(2) of TVC, EC and GEC, respectively. In both laboratory- and abattoir-based trials, TVC reductions on beef achieved by the Shellac hide treatment were superior to those achieved by the comparative sanitizer rinse-vacuum hide treatment, but reductions of EC and GEC did not differ significantly between the two hide treatments.

Treatment of cattle hides with Shellac-in-ethanol solution to reduce bacterial transferability--a preliminary study.

A solution of natural, food-grade resin (Shellac) in ethanol was evaluated to treat samples of visually clean and dry cattle hides with the aim to reduce bacterial removability from the hides by swabbing. Hide treatment by 23% Shellac-in-ethanol solution reduced sponge-swabbing recoveries of general microflora (TVC) by a factor of 6.6 logs (>1000-fold larger than the 2.9 log reduction observed by ethanol alone), and of generic Escherichia coli and Enterobacteriaceae by factors of at least 2.9 and 4.8 logs, respectively. These reductions were superior to those achieved by a sanitizer rinse-vacuum hide treatment. Significantly greater reductions of TVC recoveries from hides were achieved when using higher Shellac concentrations (23 and 30% rather than 4.8-16.7%) and when Shellac solution temperatures were 20-40 degrees C rather than 50-60 degrees C. Furthermore, the Shellac-based treatment also markedly reduced the E. coli O157 prevalence (3.7-fold reduction) on natural, uninoculated hides, as well as the counts of E. coli O157 on artificially inoculated hides (2.1 log reduction). This preliminary study indicated that a "bacterial on-hide immobilisation" approach to reducing transmission of microorganisms from cattle hide is promising and so will be further explored.

Potential for the cross-contamination of the hides of cattle while they are held in lairage.

Foodborne pathogens that may contaminate the carcase are often found on the hides of cattle presented for slaughter for human consumption, and can be transferred from animal to animal during the immediate preslaughter phase. This study quantifies the opportunities for such cross-contamination to occur during lairage of cattle. Cattle were most active in the first 10 minutes of holding, when at 2.5 m(2) or less space allowance per animal there were 12.55 animal-to-animal and 0.99 animal-to-wall contacts per minute, compared with 8.17 and 0.60 per minute, respectively, in the subsequent 20 minutes. During holding, contact between animals can be reduced by manipulating the stocking density. When the animals were given 2.5 m(2) or more each, there were 9.63 animal-to-animal contacts per minute over 30 minutes holding, whereas at 5 m(2) or more, there were only 1.71 contacts per minute. Whatever the space allowance, animal-to-wall contacts were 0.66 to 0.73 per minute over 30 minutes' holding. When space allowance is optimised, contacts with the lairage structure become more important than contacts between animals. The immediate preslaughter handling equipment (race, crush and stun box) was a significant source of potential indirect cross-contamination.

The occurrence of Escherichia coli O157 in/on faeces, carcasses and fresh meats from cattle.

The aim of this study was to investigate whether Escherichia coli O157 is present in/on raw beef in Serbia. Correlated faecal and carcasses samples from 115 slaughtered cattle plus 26 uncorrelated carcass samples were examined. E. coli O157 detection and identification was performed using selective enrichment and immunomagnetic separation followed by selective media-plating and biochemical tests. The E. coli O157 occurrences were 2.6% in faeces and 2.8% on carcasses. The E. coli O157 occurrences were 0%, 6.2% and 2.1%, respectively, in 106 samples of beef trimmings, 48 samples of minced beef and 48 samples of batter intended for production of raw, fermented sausages. The results confirmed that faecal contamination is very important for the occurrence of E. coli O157 on beef carcasses. Furthermore, the present study revealed occasional presence of the pathogen in raw materials used for producing raw, fermented beef sausages.

Occurrence of Escherichia coli O157 on hides of slaughtered cattle.

AIMS: To obtain the first information on the occurrence of Escherichia coli O157 on hides of slaughtered cattle in Serbia. METHODS AND RESULTS: A total of 355 swabs were taken on the slaughterline from five areas of hide of each of the 71 cattle in a single commercial abattoir in Serbia. Using an ISO method incorporating enrichment and immunomagnetic separation steps, E. coli O157 was isolated from the hides of 20 animals (28 x 2%). With respect to different areas of the hides, the occurrence of the pathogen was, in decreasing order: hooves (11 x 3%), brisket (8 x 4%), rump (7 x 0%), neck (4 x 2) and flank (2 x 8%). In addition, factors that had more or less effects on the occurrence included visible dirtiness of the hide, cattle's age category, geographical origin of the animals and season. CONCLUSIONS: This study revealed the presence of E. coli O157 in the beef chain in Serbia and confirmed hide as an important potential source of related contamination of beef carcasses. Therefore, incorporation of preskinning hide decontamination treatments into HACCP-based slaughterline hygiene control measures could be very useful. SIGNIFICANCE AND IMPACT OF THE STUDY: The results will enable further optimization of necessary measures along the beef chain to reduce the E. coli O157 risks in Serbia.

Microbial safety of meat in the European Union.

The two most frequently reported zoonotic diseases in humans in the EU in 2005 were Campylobacter and Salmonella infections with incidences of 51.6 and 38.2 cases per 100,000 population, respectively. Reported human infections caused by Yersinia spp., Verocytotoxigenic Escherichia coli, and Listeria monocytogenes had comparably lower incidences of 2.6, 1.2 and 0.3 cases per 100,000 population, respectively. Meat and meat products are important sources for these infections but knowledge on exactly how important they are compared with other types of food, drinking water and environmental exposure is quite limited. Occurrences of zoonotic pathogens in raw meat are variable, although most often are between 1% and 10%, depending on the organism, geographical factors, farming and/or meat production practices, etc. Zoonotic pathogens in meat have to be controlled through a complete, continuous farm-to-fork system. It is of utmost importance to control faecal contamination of carcasses through efficient HACCP-based process hygiene management systems.

Microbiological differences between cull cattle slaughtered at an abattoir and cull cattle slaughtered on farms.

Tissue samples from 27 casualty adult dairy cattle slaughtered on farms and 32 'normal' cull dairy cattle were analysed microbiologically for total viable counts (tvc), Enterobacteriaceae, Escherichia coli o157, Salmonella enterica and Campylobacter species. Overall the counts of Enterobacteriaceae and tvc were higher in the animals slaughtered on farms, particularly in the spleen. One 'normal' animal yielded E coli O157, and one yielded Campylobacter jejuni, and eight of the cattle slaughtered on farms yielded C jejuni and five yielded S enterica.

An evaluation of simple cleaning methods that may be used in red meat abattoir lairages.

Concrete tiles artificially contaminated with field strains of Escherichia coli and Salmonella kedougou, with and without the presence of bovine faecal matter, to simulate visually clean and visually dirty surfaces respectively, were cleaned using a specially designed mechanical rig. Cleaning was carried out using (1) water under mains pressure, (2) water under pressure, (3) water under pressure with a proprietary sanitising agent, (4) steam under pressure and combinations of (5) mains water followed by steam under pressure or (6) water under pressure followed by steam under pressure. Thirty replicates of each of visually clean and visually dirty concrete surfaces were cleaned using each method. Where there was no faecal matter, the use of a proprietary sanitiser at maximum recommended concentration, or the application of steam under pressure gave greater reductions in microbial contamination than the use of mains or a pressure wash. Where the surface was visually contaminated with the faecal material, the use of a pressure wash followed by immediate steam application gave reductions in microbial contamination comparable with the use of a proprietary sanitiser at maximum recommended concentration. The use of steam alone on a visually dirty surface was not an effective means of reducing microbial contamination. A small pilot trial under commercial conditions ranked the efficacy of cleaning treatments as follows: pressure washing followed immediately by steam application was the best method of cleaning a holding pen floor, followed by use of a sanitising agent at the greatest concentration recommended by the manufacturer, and then by pressure washing alone. Pressure washing followed by a delayed steam application appeared to give a poor final result on the surface.

Construction, management and cleanliness of red meat abattoir lairages in the UK.

A survey of a large number of UK abattoirs was conducted via a questionnaire designed to obtain information on (i) throughput and species slaughtered; (ii) construction materials used; (iii) use and type of bedding and (iv) details of cleaning/sanitation regimes. A representative group of abattoirs were selected on the basis of the responses to the questionnaire, and the lairage at these plants investigated through enumeration of Escherichia coli remaining after routine cleansing operations. The aim of this study was to enable identification of "common lairage practices" and to assess the general status of the lairage hygiene and effectiveness of lairage cleaning in commercial UK abattoirs. The study shows that microbial contamination often remains in UK lairage holding pens after routine cleaning operations. It would appear that there are significant differences in the effectiveness of lairage cleaning programmes at commercial abattoirs, and that the stun-box-roll-out areas are often cleaned to a better standard than the holding areas. As a result of persistence of microbial contamination in the lairage, there is a possible risk of foodborne pathogens persisting in the environment and potentially contaminating animals and carcasses processed on subsequent days.

Presence of Salmonella in the red meat abattoir lairage after routine cleansing and disinfection and on carcasses.

Foodborne pathogens, such as Salmonella, may remain in abattoir lairages after cleansing and pose a risk of transfer and contamination from one processing day to the next. These organisms may be transferred to the outer surface of animals held in lairage facilities, and the skin or hide may be a significant source of microbial contamination on the red meat carcasses subsequently produced. Sponge samples were taken from various sites in the lairage (n = 556), and single-pass sponge samples were taken from one side of red meat carcasses (n = 1,050) at five commercial abattoirs in Southwest England and tested for the presence of Salmonella. Of these, 6.5% of lairage samples were positive, containing estimated numbers of up to 10(4) Salmonella organisms per sampled area (50 by 50 cm). Salmonella was found on 9.6% of 240 lamb carcasses, 12.7% of 330 beef carcasses, 31% of 70 pig carcasses, 20% of 80 calf carcasses younger than 14 days of age, and none of 330 cull cow and bull carcasses. Subtyping divided the 137 isolates into seven serogroups and three pulsed-field gel electrophoresis clusters, and sensitivity testing against a bank of 16 antimicrobials indicated that 47 isolates had resistance to one or more antimicrobial agents. These results indicate that Salmonella contamination can persist in the lairage environment from one processing day to the next and that Salmonella is present on red meat carcasses, although the implications of residual lairage contamination on carcass meat microbiology are not clear from this study. Abattoir owners should take steps to reduce the level of contamination in their premises to prevent contamination from being carried over from one processing day to the next.

An evaluation of selected methods for the decontamination of cattle hides prior to skinning.

The effectiveness of different decontamination treatments in reducing microbial loads on cattle hides was assessed. The 10-s hide treatments were conducted using a wet-and-dry vacuum cleaner filled with one of the liquids (heated to 50 °C) indicated below, followed or not by 10-min drying in the air. Also, the hide was clipped, followed or not by 10-s singeing using a hand-held blowtorch. Before and after each decontamination treatment, the hide was sampled (100 cm(2) areas) by a sponge-swabbing method to compare the total viable counts of bacteria (TVC). The largest bacterial reduction (P<0.001; 2.31log(10) cfu/cm(2)) was achieved by singeing of previously clipped hide. Treatment of hide with a food industry sanitizer solution (10% Betane Plus) resulted in significant reductions of 1.80 (P<0.001) and 1.98log(10) cfu/cm(2) (P<0.001) without and with subsequent drying, respectively. Treatment of hide with a food industry disinfectant (P3-Topactive DES) significantly reduced TVC by 0.97 (P<0.001) and 1.18log(10) cfu/cm(2) (P<0.001) without and with subsequent drying, respectively. Treatments of hide with water alone or with a food-safe detergent solution (Formula 963B), or hide clipping alone, did not produce significant decontamination effects. Since hide contamination is associated with microbial contamination of the carcasses, the results indicate that post-killing/pre-skinning hide decontamination (used alone, or in combination with carcass decontamination) has a potential to improve microbial meat safety. Nevertheless, further research is required to optimise the efficacy of these treatments in the reduction of specific pathogens under commercial conditions.

Spread of marker bacteria from the hides of cattle in a simulated livestock market and at an abattoir.

The spread of microbial contamination on the hides of beef was investigated at two stages in the meat chain: (i) in a simulated livestock market ("the market") using 33 animals, and (ii) in the unloading-to-skinning area of a commercial abattoir using 18 animals. At both stages, harmless bacterial markers (nalidixic acid-resistant Escherichia coli K-12; rifampicin- and nalidixic acid-resistant Pseudomonas fluorescens; and a tetracycline-resistant E. coli) were inoculated on the hides of a small number of selected animals, and their transfer to other animals and the environment was examined. At the market, the initial prevalence of animals positive for the hide markers (9.1% in each phase) introduced in the presale pen, sale ring, and postsale pen changed to 39.4, 15.1, and 54.5%, respectively, by the end of the market process. In addition, widespread contamination of the market environment with the hide markers was observed. At the abattoir, the initial prevalence of animals positive for the hide marker (11.1%) inoculated at unloading increased to 100% (hide before skinning) and 88.8% (skinned carcass). In addition, another marker inoculated on environmental surfaces in lairage pens, races, and stunning box was detected on 83.3% (hide before skinning) and 88.8% (skinned carcass). These results, although obtained with a relatively small number of animals, demonstrate that both the livestock market process and the unloading-to-skinning process at abattoirs can facilitate the extensive spread of microbial contamination on hides not just within, but also between, batches of animals.

Pulsed field gel electrophoresis of related Escherichia coli O157 isolates associated with beef cattle and comparison with unrelated isolates from animals, meats and humans.

The pulsed field gel electrophoresis (PFGE) diversity of 51 related Escherichia coli O157 isolates, associated with beef cattle from a single-farm-to-single abattoir (SF-SA) chain of events was determined. The 51 related E. coli O157 isolates from hides, faeces or carcasses of SF-SA cattle produced 11 different PFGE profiles. Also, the PFGE diversity of 6 isolates, associated with a second cattle abattoir, was determined; only two PFGE profiles were found. On the other hand, the PFGE diversity of 136 unrelated E. coli O157 isolates (from healthy meat animals, retail meats and cases of human disease) was also determined. The 136 unrelated E. coli O157 isolates produced 78 different PFGE profiles, most of which (approximately 70%) comprised only one isolate. Overall, the results showed: (a) related E. coli O157 isolates (from both SF-SA events, and the second abattoir) had a markedly narrower clonal profile than the 136 unrelated E. coli O157 isolates; (b) the isolation of identical PFGE types from hide, lairage environment, and carcasses confirms the significance of cross-contamination (both pre-slaughter and during skinning) taking place at abattoirs; and (c) PFGE typing of isolates offers a good tool for tracking sources/routes of such cross-contamination. Such cross-contamination may lead to originally E. coli O157-free animals (and resultant carcasses) becoming contaminated during farm-slaughter-dressing chain of events, so development of efficient control strategies is required.

A comparison of acute phase protein measurements and meat inspection findings in cattle.

The acute phase proteins haptoglobin (Hp) and serum amyloid-A (SAA) are increased in the blood of cattle with infectious or inflammatory diseases. As it is important to identify such cattle at meat inspection, a study was undertaken to compare the levels of Hp and SAA in blood samples from cattle at abattoir with the post-mortem meat inspection findings. The serum concentrations of Hp and SAA were determined in healthy beef cattle (n = 16); healthy dairy cows with no pathological conditions (n = 22); and cows with pathologic conditions (n = 62). The last group was subdivided into cows with acute pathological conditions (n = 10) and those with non-acute pathological conditions (n = 52). The mean (+/-SD) Hp levels in plasma from beef cattle and cows without pathological conditions found were 0.11 +/- 0.08 mg/mL and 0.02 +/- 0.03 mg/mL, respectively, and the difference was statistically significant (p < 0.001). However, mean Hp level in cattle with pathological conditions was 0.27 +/- 0.40 mg/mL, significantly higher than the mean values of either group of healthy animals (p < 0.01 versus healthy dairy cows and p < 0.001 versus healthy beef cattle). The mean SAA concentration in plasma samples from 22 healthy dairy cows (with no pathological conditions found) was 51 +/- 38 microg/mL, significantly higher (p < 0.01) than the mean SAA value of 29 +/- 21 microg/mL calculated from 16 plasma samples from healthy beef cattle. In the group of 62 cows with pathological conditions, the mean SAA level was 94 +/- 115 microg/mL being significantly higher than the respective value in either groups of healthy animals (p < 0.01 versus healthy cows and p < 0.001 versus healthy beef cattle). Considerations of the acute phase proteins results obtained from the animals with pathological conditions did not reveal a clear association between acute phase proteins levels and respective specific pathological conditions, although there was a significant correlation between Hp and SAA concentrations at the individual animal level when all results were considered (R = 0.75, n = 100, p < 0.001). Nevertheless, when the dairy cows with pathological conditions were subdivided, some significant differences in mean values of acute phase proteins were observed enabling differentiation between animals with (broadly categorised) acute and non-acute pathological conditions. Significantly higher Hp (p < 0.05) and SAA (p < 0.05) concentrations were found in the acute pathology group than in the non-acute pathology group. Overall, the result of the present study indicated that the acute phase protein analysis could be an additional and useful tool enabling separation of "suspect" from "non-suspect" animals during ante mortem inspection within a modernised meat inspection system.

Conditions in lairages at abattoirs for ruminants in southwest England and in vitro survival of Escherichia coli O157, Salmonella Kedougou, and Campylobacter jejuni on lairage-related substrates.

Information on lairages (regarding design, construction materials, and use of bedding and cleaning regimes) was collected for 21 commercial cattle and/or sheep abattoirs in southwest England. Overall, roughened or grooved concrete was the most common lairage flooring material. Straw bedding was used in the majority of lairages and was changed between animal batches, daily, weekly, and monthly in roughly 5, 60, 15, and 10%, respectively, of the surveyed lairages. Lairages were commonly washed with cold water with no detergents and/or disinfectants, and only about half the lairages were washed daily. Also, a three-pathogen cocktail inoculum comprising Escherichia coli O157 (NCTC 12900), Salmonella Kedougou (VLA S488/01), and Campylobacter jejuni (VLA C4) (at 8, 8, and 7 log CFU/ml or 8, 8, and 7 log CFU/g, respectively) was suspended in either broth (for nonfecal contamination) or bovine feces (for fecal contamination). Samples of the four most common substrates present in lairages (concrete, straw, metal, and hide) were contaminated in vitro with either fecal or nonfecal inocula and subsequently held in the laboratory at 10 or 25 degrees C for 1 week. Bacterial counts for these samples were monitored daily and used to assess the number of days required for a 90% reduction of each pathogen population. In most cases, pathogens survived for >1 week, with survival rates being higher for straw or hide than for concrete or metal and higher for fecal contamination than for nonfecal contamination. Overall, if survival rates for the three pathogens under practical lairage conditions were similar to the in vitro survival rates found in this study, contamination of lairages with pathogens could be carried over from one batch of animals to another and/or from one day to the next.

Escherichia coil O157 diversity with respect to survival during drying on concrete.

Shiga toxin (Stx)-producing Escherichia coli O157 isolates (n = 123) were divided into groups according to origin, genotype (pulsed-field gel electrophoresis [PFGE] type, or ribotype), type of Stx produced, or phage type (PT). The survival rate ([number of CFU after 24 h of drying/number of CFU before drying] x 100) for each isolate was determined in triplicate after drying on concrete for 24.0 h. The overall mean survival rate among the 123 E. coli O157 isolates studied was 22.9%, but there was a wide range of responses to drying on concrete, with a minimum of 1.2% and a maximum of 61.9% of the initial inocula being recovered after drying. Among the groups, those isolates that originated from cases of human disease were, on average, significantly more sensitive (P < 0.001) to drying (with a mean survival rate of 15.3%) than isolates from the other three sources (with mean survival rates of 27.7, 26.0, and 22.9% for meats, bovine or ovine feces, and bovine hides, respectively). When the isolates were grouped by genotype, three of the PFGE types were, on average, significantly more resistant to drying than two other PFGE types were, and similarly, significant differences in average resistance to drying between groups of E. coil O157 with different ribotypes were seen. There were no differences between the abilities of isolates producing different Stxs (Stx 1 or Stx 1 and Stx 2) to survive drying. E. coli O157 isolates of PT4, PT21/28, and PT32 survived drying on concrete better than groups of other PTs did. Since the E. coli O157 isolates had various abilities to survive drying on concrete, drying could contribute to a kind of E. coil O157 natural selection along the meat chain. This possibility may have significant meat safety implications if a range of E. coil O157 isolates are simultaneously exposed to drying at any point along the meat production chain. Those E. coil O157 isolates that are more able to survive drying could be more likely to pass farther along the meat chain and ultimately reach consumers.

Combined use of two genetic fingerprinting methods, pulsed-field gel electrophoresis and ribotyping, for characterization of Escherichia coli O157 isolates from food animals, retail meats, and cases of human disease.

Two genetic fingerprinting techniques, pulsed-field gel electrophoresis (PFGE) and ribotyping, were used to characterize 207 Escherichia coli O157 isolates from food animals, foods of animal origin, and cases of human disease (206 of the isolates were from the United Kingdom). In addition, 164 of these isolates were also phage typed. The isolates were divided into two general groups: (i) unrelated isolates not known to be epidemiologically linked (n = 154) and originating from food animals, foods and the environment, or humans and (ii) epidemiologically related isolates (n = 53) comprised of four related groups (RGs) originating either from one farm plus the abattoir where cattle from that farm were slaughtered or from one of three different English abattoirs. PFGE was conducted with the restriction endonuclease XbaI, while for ribotyping, two restriction endonucleases (PstI and SphI) were combined to digest genomic DNAs simultaneously. The 207 E. coli O157 isolates produced 97 PFGE profiles and 51 ribotypes. The two genetic fingerprinting methods had similar powers to discriminate the 154 epidemiologically unrelated E. coli O157 isolates in the study (Simpson's index of diversity [D] = 0.98 and 0.94 for PFGE typing and ribotyping, respectively). There was no correlation between the source of an isolate (healthy meat or milk animals, retail meats, or cases of human infection) and either particular PFGE or ribotype profiles or clusters. Combination of the results of both genetic fingerprinting methods produced 146 types, significantly more than when either of the two methods was used individually. Consequently, the superior discriminatory performance of the PFGE-ribotyping combination was proven in two ways: (i) by demonstrating that the majority of the E. coli O157 isolates with unrelated histories were indeed distinguishable types and (ii) by identifying some clonal groups among two of the four RGs of E. coli O157 isolates (comprising PFGE types different by just one or two bands), the relatedness of which would have remained unconfirmed otherwise.

Pulsed-field gel electrophoresis characterization of Shiga toxin-producing Escherichia coli O157 from hides of cattle at slaughter.

Contamination of the brisket areas of the hides of healthy adult cattle with Shiga toxin-producing Escherichia coli O157 at slaughter in England was studied. In total, 73 cattle consignments comprising 584 animals delivered to one abattoir over 3 days during 1 week in July 2001 were studied: 26 cattle consignments arriving on Monday, 32 consignments arriving on Wednesday, and 15 consignments arriving on Friday. Consignment sizes ranged from 1 to 23 animals, with a mean consignment size of 8. The hide of the first animal to be slaughtered in each consignment was sampled by using a sponge swab moistened with 0.85% saline to rub an unmeasured brisket (ventral) area (ca. 30 by 30 cm). The process of isolating E. coli O157 from the swabs consisted of enrichment, screening with immunoprecipitation assay kits, and immunomagnetic separation. E. coli O157 was found on 24 of 73 (32.9%) cattle hides examined, and 21 of these 24 isolates produced Shiga toxins. The 24 E. coli O157 isolates produced six different pulsed-field gel electrophoresis profiles, and 18 (75%) of the isolates were of one prevalent clone. The high prevalence of one E. coli O157 clone on the hides of cattle at slaughter could be due to a high prevalence of that clone on the 18 farms involved (not investigated in the current study), in the postfarm transport or lairage environments, or both. Since the lairage environment, but not the farm of origin or the postfarm transport vehicle, was a factor common to all 18 cattle consignments, it could have played an important role in spreading the prevalent E. coli O157 clone to the cattle hides. Lairage pen floors and the stunning box floor were identified as the most probable sites along the unloading-to-slaughter route at which the brisket areas of cattle hides could become contaminated.

Potential for the spread of Escherichia coli O157, Salmonella, and Campylobacter in the lairage environment at abattoirs.

Prevalences of Escherichia coli O157, Salmonella spp., and Campylobacter spp. were examined in 270 swabs taken from selected sites along the unloading-to-slaughter routes of animal movement in lairages of six commercial abattoirs, three for cattle and three for sheep. The overall prevalences of the pathogens in the respective lairage environments were compared with those for 270 swabs from the pelts of 90 lambs examined in the present study and 270 swabs from the hides of 90 cattle examined in a previous study that were slaughtered at the same abattoirs on the same days. Also, the results obtained were analyzed with the aim of identifying critical points at which animal-environment-animal transfer of the pathogens in lairages occurs. The results showed that (i) the overall prevalences of E. coli O157, Salmonella spp., and Campylobacter spp. were 27.2, 6.1, and 1.1%, respectively, in cattle lairages and 2.2, 1.1, and 5.6%, respectively, in sheep lairages; (ii) the overall prevalences of the three pathogens on cow hides (28.8, 17.7, and 0%, respectively) and sheep pelts (5.5, 7.8, and 0%, respectively) were higher than the overall prevalences in the respective lairage environments; (iii) the most frequently contaminated sites in cattle lairages were holding pen floors (50% of swabs positive for one or more pathogens), entrance gates of stun boxes (27.8% of swabs positive for one or more pathogens), and stun box floors (22.2% of swabs positive for one or more pathogens); (iv) the most frequently contaminated sites in sheep lairages were unloading ramp floors, holding pen floors, and water troughs (33.3, 22.2, and 22.2%, respectively); and (v) overall, cattle lairages and cow hides were more frequently contaminated with the pathogens than were lamb lairages and lamb pelts. Further research is needed to develop strategies for the incorporation of pathogen control in lairages into integrated microbial meat safety systems.