Assessment of beef carcass contamination with Salmonella and E. coli O 157 in slaughterhouses in Bishoftu, Ethiopia

Abstract

Abstract Background Salmonella and E. coli O157 are common causes of foodborne diseases. Evisceration and de-hiding steps can lead to carcass contamination during slaughter operation. In Ethiopia, information on the association between the presence of these pathogens in the rectal content and/or on the hide of cattle and their presence on the carcass is lacking. Methods The aim of this study was to assess the sources of beef carcass contamination with Salmonella and E. coli O157 during slaughter. Rectal contents and hide- and carcass-swabs (from three sites: foreleg, brisket and hind leg) were collected from 70 beef cattle at two small scale slaughterhouses. Isolates were genotyped by the Pulsed Field Gel Electrophoresis method and tested for resistance against 14 microbial drugs. Results Salmonella was detected at equal proportions (7.1%) in rectal content samples and hide swabs. E. coli O157 was detected in 8.6% of the rectal contents and 4.3% of the hide swabs. The proportion of contaminated carcasses was 8.6% for Salmonella and 7.1% for E. coli O157. Genetic linkage between the Salmonella and E. coli O157 isolates from the rectal contents and/or hides and carcasses were observed only in a few cases (2 and 1 carcasses, respectively) indicating the limited direct transfer of the pathogens from the feces and/or hide to the carcass during slaughter. Most carcasses became positive by cross contamination. All the S. Typhimurium isolates (n = 8) were multidrug resistant being resistant to ampicillin, chloramphenicol, sulfamethoxazole and tetracycline. The two S. Dublin isolates were resistant to colistin. All E. coli O157 isolates were susceptible to the antimicrobials tested. Conclusion The results indicated that cross contamination may be an important source for carcass contamination.