Browsing by Author "Echeverry, Alejandro"
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Item Development and validation of intervention strategies to control Escherichia coli O157:H7 and Salmonella Typhimurium Dt 104 in needle tenderized and injected beef (USDA choice strip loins - longissimus lumborum) under two simulated industrial conditions(Texas Tech University, 2007-12) Echeverry, AlejandroAfter investigation by state health departments and the Center for Disease Control and Prevention, three different outbreaks between 2000 and 2004 were linked to the consumption of non-intact products contaminated with Escherichia coli O157:H7. Following this, in May 2005, the USDA-FSIS published notice that establishments who produce mechanically tenderized and moisture enhanced beef products were required to reassess their HACCP plans due potential contamination risk to consumers. The purpose of this study was to determine the effectiveness of different intervention strategies to control E. coli O157:H7 and Salmonella enterica serotype Typhimurium definitive phage type 104 in needle tenderized and enhanced beef strip loins. Treatments included a) lactic acid producing bacteria (LAB; ~107 cfu/g), acidified sodium chlorite (ASC; 1000 ppm), and lactic acid (LA; 3%) which were evaluated under two application scenarios: packer and purveyor. Packer samples were treated immediately after fabrication, whereas purveyor samples were treated after aging. Samples were aged for 14 or 21 days prior to needle tenderization or enhancement followed by microbial enumeration on the surface and at two internal subsections within the product. Salmonella and E. coli O157:H7 were significantly reduced by all interventions upon initial application. At the packer setting, Salmonella surface counts on day 14 were significantly reduced by all interventions in enhanced and needle tenderized beef. On day 21 all interventions were significantly effective in reducing pathogen levels in needle tenderized beef; however, only LAB and LA were significant in enhanced samples. At the purveyor setting, Salmonella surface counts on day 14 were significantly reduced by LA (needle tenderized beef) and LAB (enhanced beef). At the purveyor setting no differences between interventions were observed on day 21. E. coli O157:H7 surface counts at the packer setting were significantly reduced in needle tenderized beef on day 14 by the application of LA; however, no differences were observed on enhanced samples. On day 21 all interventions were significantly effective in reducing pathogen counts. At the purveyor setting, E. coli O157:H7 was reduced significantly from needle tenderized and enhanced beef only by application of LAB (Day 14 and 21). Internal E. coli O157:H7 counts were significantly reduced by 90% or more by using LAB, LA and ASC. A > 2 log reduction in the E. coli O157:H7 counts were observed after treatment with the interventions on day 14 in needle tenderized and injected beef. On day 21, ASC and LA reduced E. coli O157:H7 by up to 3 logs while LAB showed 2.0 log reductions. Internal Salmonella counts were reduced by > 2.0 log after 14 days using LAB and LA, and were significantly reduced by all interventions by day 21 of aging. Results from this study indicate that application of LAB, ASC, and LA sprays reduced E. coli O157:H7 and Salmonella enterica serotype Typhimurium definitive phage type 104 in beef subprimals with varying degrees of efficacy depending on time, location, and application setting.Item Survival and distribution of Escherichia coli O157 in bovine manure(Texas Tech University, 2004-12) Echeverry, AlejandroEscherichia coli 0157:H7 has become one of the most important emerging foodborne pathogens with many recent outbreaks being associated with cattle. Although estimates of E. co//0157:H7 prevalence in cattle have increased over time likely due improvements in detection methodologies, fecal collection methodologies and sample transport conditions from farm to microbiological laboratories for further analysis may be factors for underestimation of prevalence of this pathogen. In this study, a new sampling methodology was analyzed and comparison of survival of E. coli 0157:H7 in feces of cattle under various experimental conditions was also determined. For the first part of the study, bovine fecal samples were inoculated with a cocktail of four different antibiotic resistant E. co//0157:H7 strains. Each inoculated sample was subdivided and subjected to each of the four following conditions: 37°C, room temperature (23''C), refrigeration temperature (4.4°C) and in plastic coolers with refrigerant packs in order to simulate transportation conditions. Samples from each of the temperature conditions were taken at 0 h, 24 h, 48 h, 120 h, and 144 h and subjected to detection and quantification of E. coli 0157:H7. Overall, holding samples at temperatures equal to or below to 23° C resulted in detectable populations for up to 168 h. At 37°C, samples were not recovered by any of the methods used after 48 hours. These results indicate that holding samples at room temperature or lower for up to 168 h prior to processing will not reduce the pathogen's population. For the second part of the study, the objective was to evaluate fecal pat sampling strategies to improve accuracy of E. co//0157:H7 prevalence estimates. A total of 120 fresh fecal pats from cattle were used in this study. From each fecal pat five samples were collected systematically going from West to East (positions 1 to 5 respectively) in north to south lines direction to avoid cross contamination and cultured for E. coli 0157:H7 within two hours using IMS separation. Of the 120 fecal pats, 96 (80%) had no positive samples in any of the 5 samples. One sample was positive in 13 of the pats, 2 in 4 of the pats, 3 in 2 of the pats, 4 in 3 of the pats and only 2 of the pats had all 5 samples positive. Of the 600 total sub-samples analyzed, 49 were positive with 14, 9, 8, 8, and 10 on position 1,2,3, 4, and 5 respectively. An increase in the prevalence of 2.45-fold (from 8.17% to 20%) was observed when sampling 5 positions per fecal pat as compared to the estimated prevalence obtained when just 1 sub-sample was obtained. Prevalence estimates may be underestimated as a result of an uneven distribution in fecal material; therefore sampling procedure plays a critical role in E. co//0157:H7 detection in bovine fecal pats.