The effects of transport and lairage on counts of Escherichia coli O157 in the feces and on the hides of individual cattle.

OBJECTIVES: The main objective of this study was to determine the impact of transport and lairage on the isolation rate and the number of Escherichia coli O157 on cattle. MATERIALS: Ninety animals, divided into three groups (A, B, and C) of 30 animals each, were used in this study. Individual animals were tagged, and samples were collected from the hides and feces of each at a feedlot and again after slaughter. The carcass of each animal was also sampled. Samples were also collected from the feedlot pens, the sides and floors of the transport trucks, and abattoir holding pens. The isolation rate and the number of E. coli O157 were estimated using a combination of immunomagnetic separation and the Most Probable Number technique. RESULTS: Cattle hides were more likely to be contaminated with E. coli O157 at the feedlot (31%) than at the abattoir (4%). E. coli O157 was detected in 18% and 12% of cattle feces collected at the feedlot and after slaughter, respectively. E. coli O157 was isolated from truck floors (26%), truck sides (11%), abattoir pen rails (47%), and pen floors (42%). The mean count of E. coli O157 in positive feces was log(10) 1.17 and 2.37 MPN/g at the feedlot and slaughter, respectively. A 3 log(10) increase in the number of E. coli O157 was observed between the feedlot (2.66 MPN/g) and slaughter (5.66 MPN/g) in the feces of one animal in group B. E. coli O157 was isolated from the hide and carcass of this animal. CONCLUSIONS: Transport and lairage did not lead to an increase in the number or isolation rate of E. coli O157 from cattle. APPLICATIONS: Intervention strategies for reducing E. coli O157 contamination of cattle carcasses should target mechanisms that limit the impact of animals shedding a high number throughout production and processing.

Use of routine beef carcase Escherichia coli monitoring data to investigate the relationship between hygiene status of incoming stock and processing efficacy.

In Australian export-registered abattoirs microbiological monitoring is carried out within the E. coli and Salmonella Monitoring (ESAM) program. During the calendar year 2003, the ESAM database indicated a national prevalence of Escherichia coli of around 3.0% for steers/heifers and 7.1% for cows/bulls. An investigation was carried out to attempt to elucidate why some establishments had E. coli prevalence markedly higher or markedly lower than the national average. The investigation was based on a questionnaire completed by fifteen export establishments which provided data on livestock, processing, operator training and management. The responses were verified by site visits and then evaluated for their relationship with ESAM data on E. coli in two stages. In stage 1, E. coli prevalence for each abattoir was plotted against each variable recorded by the questionnaire; no single variable was a reasonable predictor for prevalence of E. coli on carcases. In stage 2, variables influencing contamination were grouped under two categories: contamination on incoming livestock (Problem variables) together with the ability of the plant's process to deal with such contamination (Process variables). The analysis prompted two main conclusions. Firstly, plants with a large incoming problem with livestock (long haul, high tag score and proportion of cows/bulls slaughtered) plus "poor" processes had higher than average E. coli prevalence. Secondly, plants with hot water decontamination systems had low E. coli prevalence even when there was a substantial incoming problem with livestock, such as a relatively high proportion of cows/bulls.

A study of the prevalence and enumeration of Salmonella enterica in cattle and on carcasses during processing.

Salmonella prevalence and counts were estimated for samples from the oral cavity, hide, rumen, and feces of 100 cattle at slaughter and from the pre- and postchill carcasses of these cattle. Samples were collected from 25 consecutively slaughtered cattle from each of four unrelated groups slaughtered at a single abattoir on different days. Ten additional fecal samples from each group were collected from their respective abattoir holding pens prior to slaughter. The prevalence of Salmonella was estimated using automated immunomagnetic separation, and the counts were estimated using a combination of most probable number (MPN) and automated immunomagnetic separation. A total of 606 samples were collected with Salmonella isolated from 157 (26%), including 29% of oral cavities, 68% of hides, 16% of feces collected after evisceration, 25% of rumen samples, 2% of prechill carcasses, 3% of postchill carcasses, and 48% of feces collected from holding pens. The prevalence and count of Salmonella varied between the different groups of animals tested. The highest count obtained was from a rumen sample (1.1 x 10(4) MPN/g). Other counts were generally low, with a maximum count in feces collected after evisceration and in the abattoir holding pens of 93 and 23 MPN/g, respectively. The highest count on hides, in oral cavities, and on carcasses was 4.8 MPN/cm2, 23 MPN/g, and 0.31 MPN/cm2, respectively. Even though Salmonella was present on the hides and in the rumen and feces of at least one animal from each group of cattle, the processing of animals at this abattoir resulted in few contaminated carcasses, and when contamination occurred, Salmonella was detected at low numbers.

An investigation of Escherichia coli O157 contamination of cattle during slaughter at an abattoir.

The extent of contamination with Escherichia coli O157 was determined for 100 cattle during slaughter. Samples from 25 consecutively slaughtered cattle from four unrelated groups were collected from the oral cavity, hide, rumen, feces after evisceration, and pre- and postchill carcass. Ten random fecal samples were collected from the pen where each group of animals was held at the abattoir. E. coli O157 was detected using automated immunomagnetic separation (AIMS), and cell counts were determined using a combination of most probable number (MPN) and AIMS. E. coli O157 was isolated from 87 (14%) of the 606 samples collected, including 24% of 99 oral cavity samples, 44% of 100 hides, 10% of 68 fecal samples collected postevisceration, 6% of 100 prechill carcass swabs, and 15% of 40 fecal samples collected from holding pens. E. coli O157 was not isolated from rumen or postchill carcass samples. E. coli O157 was isolated from at least one sample from each group of cattle tested, and the prevalence in different groups ranged from less than 1 to 41%. The numbers of E. coli O157 differed among the animals groups. The group which contained the highest fecal (7.5 x 10(5) MPN/g) and hide (22 MPN/cm2) counts in any individual animal was the only group in which E. coli O157 was isolated from carcasses, suggesting a link between the numbers of E. coli O157 present and the risk of carcass contamination. Processing practices at this abattoir were adequate for minimizing contamination of carcasses, even when animals were heavily contaminated with E. coli O157.

Presence of activatable Shiga toxin genotype (stx(2d)) in Shiga toxigenic Escherichia coli from livestock sources.

Stx2d is a recently described Shiga toxin whose cytotoxicity is activated 10- to 1000-fold by the elastase present in mouse or human intestinal mucus. We examined Shiga toxigenic Escherichia coli (STEC) strains isolated from food and livestock sources for the presence of activatable stx(2d). The stx(2) operons of STEC were first analyzed by PCR-restriction fragment length polymorphism (RFLP) analysis and categorized as stx(2), stx(2c vha), stx(2c vhb), or stx(2d EH250). Subsequently, the stx(2c vha) and stx(2c vhb) operons were screened for the absence of a PstI site in the stx(2A) subunit gene, a restriction site polymorphism which is a predictive indicator for the stx(2d) (activatable) genotype. Twelve STEC isolates carrying putative stx(2d) operons were identified, and nucleotide sequencing was used to confirm the identification of these operons as stx(2d). The complete nucleotide sequences of seven representative stx(2d) operons were determined. Shiga toxin expression in stx(2d) isolates was confirmed by immunoblotting. stx(2d) isolates were induced for the production of bacteriophages carrying stx. Two isolates were able to produce bacteriophages phi1662a and phi1720a carrying the stx(2d) operons. RFLP analysis of bacteriophage genomic DNA revealed that phi1662a and phi1720a were highly related to each other; however, the DNA sequences of these two stx(2d) operons were distinct. The STEC strains carrying these operons were isolated from retail ground beef. Surveillance for STEC strains expressing activatable Stx2d Shiga toxin among clinical cases may indicate the significance of this toxin subtype to human health.