ESCHERICHIA COLI O157:H7 ISOLATION FROM FECES, SKIN AND CARCASSES AS WELL AS TOTAL AND FECAL COLIFORMS ON CARCASSES OF SMALL RUMINANTS AT AN EXPORT ABATTOIR, MOJDO, ETHIOPIA
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2008
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Abstract
The purpose of this study was to find out the presence of association between carcass contamination with E. coli O157: H7 and fecal and skin prevalence of E. coli O157: H7 and to estimate coliform loads on before and after wash of sheep and goats carcasses at an export abattoir at Modjo, Ethiopia. A total of 711 samples were examined for the presence of E. coli O157:H7 from fecal samples, skin swabs, carcass swabs before and after wash from sheep and goats slaughtered between October, 2007 and April, 2008. Water samples were also collected for the isolation of E. coli O157:H7 and coliform counts. Total and fecal coliform loads were estimated on same carcasses using Violet Red Bile Agar (VRBA). For the isolation of E. coli O157:H7, all samples were enriched with modified Tryptic Soy broth with novobiocin (mTSB+n) and concentrated using immunomagnetic separation (IMS). The bacteria-bead complex was plated onto cefixime-tellurite containing Sorbitol MacConkey agar (CT-SMAC) and presumptive colonies were confirmed by latex agglutination test as recommended by ISO16654, (2001). E. coli O157:H7 was isolated from feces (4.7%), skin swabs (8.7%), carcass swabs before wash (8.1%), carcass swabs after wash (8.7%) and water samples (4.2%), respectively. A statistically significant association was found between prevalence of carcass contamination with fecal and skin E. coli O157:H7 status. The total coliform counts before and after carcass wash were 3.15 log10CFUcm-2 (SD= 0.77) and 2.97 log10CFUcm-2 (SD = 0.82), respectively. The log10 means of fecal coliforms before and after carcass wash were 2.96 (SD=0.88) and 2.77(SD=0.91) respectively. Statistically significant difference was observed between the means of total coliform counts (P=0.002) and fecal coliform counts (P=0.001) before and after carcass wash. No fecal coliforms were isolated from water samples. PCR analysis identified both stx1 and stx2 genes from one E. coli O157:H7 isolate collected from goat carcass. The identification of this virulent factor indicates the potential of sheep and goats as sources of E.coli O157:H7 for human infection in the country. Control measures to reduce the public health risks arising from E. coli O157 in reservoir animals must be addressed at abattoir levels by reducing skin and fecal sources and carcass contaminations at different stage of slaughter operations. Applications of HACCP system are strongly recommended at the abattoirs.
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E.coli O157:H7, Coliforms, Sheep, Goat, Carcass contaminations, Abattoir