SALMONELLA AND E. COLI O157:H7 PREVALENCE IN CATTLE AND ON CARCASSES IN A VERTICALLY INTEGRATED FEEDLOT AND HARVEST PLANT IN MEXICO

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Title: SALMONELLA AND E. COLI O157:H7 PREVALENCE IN CATTLE AND ON CARCASSES IN A VERTICALLY INTEGRATED FEEDLOT AND HARVEST PLANT IN MEXICO
Author: Bravo, Claudia A
Abstract: Microbial contamination can create serious health risks and trade problems in the international food trade , this is essential for the economy of many countries . In Mexico scientific information regarding Salmonella and E . coli O157 :H7 prevalence at pre and post -harvest in Mexico is scarce . Therefore , this research has three general objectives : i ) to determine the prevalence of Salmonella and E . coli O157 :H7 in a Mexican cattle feedlots and its impact for subsequent contamination on carcasses , ii ) to determine if there is a seasonal effect on the prevalence of E . coli O157 :H7 at feed lot levels and iii ) to compare the prevalence of Salmonella and E . coli O157 :H7 on carcasses destined for different markets and processed under TIF certification in Mexico . Two -hundred -fifty animals were randomly selected and composite samples were taken from three anatomical carcass sites (inside round , hind shank and fore shank ) . Samples were taken from the hides , intestinal feces (IF ) , at pre -evisceration (PE ) , pre -cooler (PC ) and after 24 hours of dry chilling (DC ) in the coolers . Additionally , 250 samples from fecal (FL ) and water samples were taken from the lairage area . E . coli O157 :H7 and Salmonella detection was carried out using BAX (PCR ) , IMS and conventional methods . Logistic regression models were used to determine areas of highest risk . A total of 1 ,695 samples were collected from different locations of the integration , feedlot and harvesting slaughter plant . Salmonella was isolated from 52 .5 % of these samples . The highest prevalence was found in hides (92 .4 % ) , followed by feces from the holding pens (HP ) (91 .0 % ) , feces from feedlots (FL ) (55 .56 % ) , pre -evisceration (PE ) (49 .0 % ) , intestinal feces (IF ) (46 .8 % ) and pre -cooler (PC ) (24 .8 % ) for all sampling periods combined . The lowest prevalence was found in the carcasses after 24 hours of DC in the cooler (6 .0 % ) . The overall prevalence of E . coli O157 was as follows : hides 11 .7 % , intestinal feces 5 .2 % , feedlots 2 .7 % , holding pens 2 .0 % , pre -evisceration 0 .8 % , pre -cooler 0 .4 % and cooler 0 .4 % . E . coli O157 :H7 was recovered mainly in the summer , 6 .8 % (43 /632 ) , followed by winter 1 .79 % (12 /670 ) , however in spring all the samples at the feedlot and at the slaughter plant tested negative . Salmonella was recovered in all seasons with significant variations (P < 0 .0001 ) , the percentages being as follows : spring 59 .7 % (200 /235 ) , summer 53 .64 % (339 /632 ) and winter 44 .2 % (297 /672 ) . An effect due to seasonality on Salmonella and E . coli O157 :H7 was not clear . The prevalence of the carcasses destined for different markets did not show differences (P >0 .05 ) for Salmonella and /or E . coli O157 :H7 prevalence (P > 0 .05 ) . These results are an alert as to the risks of contamination in meats for these pathogens , show the necessity of implementing programs for food safety and microbiological interventions , and demonstrate the need for further research .
URI: http : / /hdl .handle .net /2346 /ETD -TTU -2011 -08 -1626
Date: 2011-08

Citation

SALMONELLA AND E. COLI O157:H7 PREVALENCE IN CATTLE AND ON CARCASSES IN A VERTICALLY INTEGRATED FEEDLOT AND HARVEST PLANT IN MEXICO. Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /ETD -TTU -2011 -08 -1626 .

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