Environmental sources within 5 feedlots were sampled for E. coli O157:H7 and O157:NM to determine the prevalence of this pathogen with a view to minimize or control its spread in the feedlot environment. Monthly samples were taken from the feedlots in the Panhandle and South Plains of Texas over a nine-month period. Samples were examined by an immunomagnetic bead separation, followed by plating onto CT-SMAC and CHROMagar O157 media. Sorbitol-negative colonies were tested using ImmunoCard Stat! E. coli O157:H7 Plus and confirmed as E. coli O157:H7, using biochemical (Vitek system) and serological tests (latex agglutination). Additionally, one hundred sponge samples were collected from the hides of stunned cattle at the slaughter plant. All isolates were subjected to rep-PCR DNA fingerprinting and antimicrobial profiling. E. coli O157 was isolated from hide (56%) and environmental samples (4%). E. coli O157 was isolated from all environmental sources, with peak prevalence during November (9%) and March (10%). At least one sample from each feedlot was positive 42% of the time. The most contaminated sites were the chute area (6%) and sludge from waste water ponds (6%). Positive samples were most frequently found from feedlot 5 (7%) and the greatest variation in positive samples between feedlots (0-34%) occurred during March. A decrease in the presence of E. coli O157 in feedlots was observed during January (0%), when ambient, water, and pond sludge temperatures were consistently low. No correlation with other environmental factors was observed. Hide was a primary source of E. coli O157 on carcasses with an overall prevalence of 56%. Of two sampling days, the number of positive hide samples varied from 14% for the first day to 98% for the second day. The total positive samples collected (environmental (47); hide (56)) were 64% H7, and 36% NM. The environmental isolates showed similar antibiotic resistance patterns, regardless of the source. Most E. coli O157 isolates from the feedlots and hides showed a high level of resistance to cephalothin (45%) and sulfisoxazole (56%). E. coli O157 isolates from feedlots were resistant to more than 10 antibiotics (9/317). All of the isolates appeared highly similar, with an average similarity of 53% by rep-PCR DNA fingerprinting.

To enhance outbreak investigations of Shiga toxin-producing Escherichia coli O157:H7, PulseNet Canada has recently applied Multiple Locus Variable Number Tandem Repeat Analysis (MLVA) as a supplemental subtyping tool in combination with the gold standard subtyping method Pulsed-field Gel Electrophoresis (PFGE) for enhanced resolution of isolates exhibiting indistinguishable/highly similar PFGE patterns. The objective was to assess the discriminatory power and level of specificity MLVA offers for outbreak detection and response. Results demonstrate that MLVA provides a statistically significant increase in discriminatory power for outbreak investigations (0.998) compared to PFGE alone (0.993). MLVA was able to provide additional resolution over PFGE analysis and generally agreed with PFGE when isolates were identical and epidemiologically linked. MLVA shows great promise as a molecular epidemiological tool to complement PFGE, as it improves case categorization during outbreak investigations, and the greatest benefits of MLVA may be realized during routine surveillance, when epidemiological information is not available.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed May 23, 2007). PDF text: viii, 161 p. : ill. (some col.) ; 1.95Mb UMI publication number: AAT 3237485. Includes bibliographical references. Also available in microfilm and microfiche formats.

This study was conducted to determine if a relationship exists between temperament, stress response, and the shedding of Escerhichia coli O157:H7. Cattle (n = 150) were evaluated for disposition and stress response before shipping to the feeding operation, upon arrival at the feedlot, at approximately 70d on feed, and prior to transport to the harvesting facility. Chute and pen scores, as well as serum cortisol concentrations, were measured in order to assess individual temperament and stress response. A temperament index was created to classify cattle as Excitable, Intermediate, or Calm. The presence of E. coli O157:H7 was determined by rectal swabs on the live cattle and swabs of colons collected postmortem at the processing facility. As expected, variables for pre-shipment temperament index, exit velocity, pen score, arrival and midpoint exit velocity, and mid-point cortisol concentrations differed (P < 0.05) greatly between temperament groups. However, pre-shipment chute scores and cortisol concentration, as well as arrival and final cortisol concentrations differed (P < 0.05) only for Excitable cattle compared to both Calm and Intermediate groups. The percentage of cattle shedding the pathogen at arrival was approximately equal between temperament groups. When sampled before shipment to the processing facility, a higher proportion (P = 0.03) of cattle displaying Calm temperaments shed E. coli O157:H7 than the other groups. Results from postmortem colon samples exhibited a similar trend. When the results from all four sampling periods were pooled, the Calm cattle had a greater numerical percentage test positive for E. coli O157:H7. However, the pooled frequency distribution is largely dictated by the results of the final sampling time. Based on these results, it appears that Excitable cattle are not more likely to shed E. coli O157:H7. In fact, it seems that Calm cattle may be equally or more susceptible to shed at later points in the feeding period. However, it is important to note that a relatively small number of the samples tested positive for E. coli O157:H7, thus, potentially causing dramatic changes in the distributions.

a b s t r a c t Meat and meat products have been implicated in outbreaks of Escherichia coli O157:H7 in most parts of the world. In the Amathole District Municipality of the Eastern Cape Province of South Africa, a large number of households consume meat and meat products daily, although the microbiological quality of these types of food is questionable. The present study investigated the prevalence of E. coli O157:H7 isolated from selected meat and meat products (45 samples each of biltong, cold meat, mincemeat, and polony) sold in this area. Strains of E. coli O157:H7 were isolated by enrichment culture and confirmed by polymerase chain reaction (PCR). Also investigated were the antibiogram profiles of the E. coli O157:H7 isolates. Five (2.8%) out of 180 meat and meat products examined were positive for E. coli O157:H7 that carried the fliCH7, rfbEO157, and eaeA genes. Two of the E. coli O157:H7 isolates were resistant against all the eight antibiotics tested. To prevent E. coli O157:H7 infections, meat and meat products such as biltong, cold meat, mincemeat and polony should be properly handled, and packed in sterile polyvinyl wrappers.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2007. / Title from title screen (site viewed Apr. 29, 2008). PDF text: xiii, 273 p. : ill. ; 2 Mb. UMI publication number: AAT 3294902. Includes bibliographical references. Also available in microfilm and microfiche formats.

Master of Science / Department of Diagnostic Medicine/Pathobiology / Daniel U. Thomson / A total of 284,300 animals from 10 commercial feedyards in Nebraska and Colorado were used to evaluate the effectiveness of a siderophore-receptor/porin protein-based vaccine under commercial feedlot conditions. Individual feedlots were assigned to 1 of 2 treatments: 1) all incoming cattle injected with 2 ml of SRP E. coli O157:H7 vaccine subcutaneously at arrival and at time of re-implant (VAC) or 2) all incoming cattle were not vaccinated, and were used as negative controls (CON). Twenty freshly voided fecal samples were taken from 5 pen floors of market ready cattle at each feedyard once a month during May, June, July, and August of 2010. Pre-harvest blood samples were collected on 3 occasions throughout the summer (June, July, and August). For each sampling month, 1 lot of 5 animals representing each feedyard was sampled. Fecal and blood samples were shipped to Epitopix, LLC for subsequent microbiology and anti-SRP antibody testing. Samples were coded such that laboratory personnel were blinded to the location and treatment of samples. Cattle receiving VAC treatment had reduced prevalence of E.coli O157:H7 in their feces relative to the E. coli O157:H7 prevalence in the feces of CON cattle (12.83% vs. 20.25% for VAC and CON, respectively; P = 0.07). Anti-SRP antibody titer was higher in the serum from VAC cattle relative to the SRP titer levels in serum obtained from CON cattle (0.622 and 0.075 for VAC and CON, respectively; P < 0.001). These data suggest that vaccination of feedlot cattle with SRP upon arrival at the feedlot and again 70-100 days pre-harvest reduces shedding of E. coli O157:H7.

This study measured and compared different temperatures and dwell times of hot water treatment on the reduction of Escherichia coli O157:H7 and Salmonella Typhimurium on beef carcass surfaces. Two different types of beef surfaces, lean and fat, were inoculated with a fecal slurry containing E. coli O157:H7 and S. Typhimurium at ca. 7-log CFU/g, washed to remove gross fecal matter, and rinsed with hot water between 66 and 82 degrees C (150 to 180 degrees F water) for either 5, 10, or 15 s. There were no differences (P > 0.05) in the log reductions of S. Typhimurium and E. coli O157:H7 on the lean surfaces for all three temperature treatments (66, 74, and 82 degrees C). Although the 15 s treatment resulted in a numerically higher log reduction than the other treatments, each of the times resulted in at least a 1 log reduction of both S. Typhimurium and E. coli O157:H7 for lean surfaces. For the fat surfaces, all time treatments for the 82 degrees C and the 10 and 15 s treatments for the 74 degrees C resulted in the highest log reduction for S. Typhimurium. The 5 and 10 s dwell times for treatments at 66 degrees C and the 5 s dwell time at 74 degrees C resulted in the lowest log reduction of S. Typhimurium and E. coli O157:H7. For E. coli O157:H7 all temperature and time treatments resulted in at least a 1 log reduction for the fat surfaces of the outside round. Therefore, hot water treatment is a proven method for reducing both coliforms and pathogenic bacteria.

The translocation of Escherichia coli O157:H7 as well as the impact of water washing and partial or complete surface trimming as possible pathogen reduction strategies were evaluated for vacuum-packaged beef subprimals destined for non-intact use. Cap-on and cap-off beef top sirloin butts were inoculated with two levels of E. coli O157:H7! a high-inoculum at approximately 10^4 CFU/cm^2 and a low-inoculum at approximately 10^2 CFU/cm^2. Following inoculation, the subprimals were vacuum packaged and stored for either 0, 14, or 28 days. Upon opening, the following sites were evaluated: exterior of the bag, purge, the inoculation site on the subprimal, the area adjacent to the inoculation site, and the surface opposite from the inoculation site. The following treatments then were applied: water wash, water wash followed by full-surface trimming, water wash followed by partial-surface trimming, full-surface trimming, full-surface trimming followed by water wash, partial-surface trimming, and partial-surface trimming followed by water wash. For both high and low inoculated top sirloin butts, contamination of adjacent and opposite surfaces was found after vacuum packaging. Of the treatments applied, water washing alone and partial-surface trimming were the least effective for both high and low inoculated subprimals. Full trimming, with or without a water wash, proved to be the most effective treatment used to reduce E. coli O157:H7 to non-detectable levels.

This study evaluated the thermal drying process commonly used by small and very small beef jerky operations in Texas. It was intended to determine the impact of relative humidity on the production of beef jerky and to provide documentation to beef jerky producers to support their Hazard Analysis and Critical Control Point programs. This project was divided into two phases: Phase I provided a low level of relative humidity (15-25%), whereas Phase II provided a high level (100%) for 25% of the cooking cycle. Both phases consisted of three trials, each representing one of the treatments (n=18) applied to the samples. The first treatment served as the control group and included samples that were non-inoculated, while the other two treatments included inoculations of samples with a bovine fecal slurry and rifampicin-resistant Salmonella Typhimurium. Each of the three treatments for both phases was analyzed for reduction of microbial levels in addition to temperature and product composition. Once the two phases had been completed and all data were analyzed, it was concluded that there was not a statistical difference between the level of reduction for Aerobic Plate Counts, coliforms, Escherichia coli and Salmonella provided by Phase I with low humidity and Phase II with high humidity. Both levels of humidity provided similar levels of reduction within each trial, suggesting that the level of humidity does not have a great impact on the level of microbial reduction achieved. However, this study did not provide the adequate level of initial inoculation levels to support the required 6.5 log reduction stated in 9 CFR 318.7. Inoculation levels were lower than 6.5 logs for all three treatments in both phases, resulting in lower levels of overall reduction. Therefore, based upon the information provided by this study, it cannot be concluded that a low level of humidity will achieve a 6.5 log reduction as mandated in 9 CFR 318.17.