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

Authors: GUTEMA, FANTA - Addis Ababa University; ABDI, RETA - Long Island University; Agga, Getahun; FIREW, SEYOUM - Addis Ababa University; RASSCHAERT, GEERTRUI - Flanders Research Institute For Agriculture; MATTHEUS, WESLEY - Mycology And Aerobiology Service, Sciensano; CROMBE, FLORENCE - Vrije Universiteit Brussel; DUCHATEAU, LUC - Ghent University; GABRIEL, SARAH - Ghent University; DE ZUTTER, LIEVEN - Ghent University

Submitted to: International Journal of Food Contamination
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2021
Publication Date: 7/4/2021
Citation: Gutema, F.D., Abdi, R.D., Agga, G.E., Firew, S., Rasschaert, G., Mattheus, W., Crombe, F., Duchateau, L., Gabriel, S., De Zutter, L. 2021. Assessment of beef carcass contamination with Salmonella and E. coli O 157 in slaughterhouses in Bishoftu, Ethiopia. International Journal of Food Contamination. 8. Article 3. https://doi.org/10.1186/s40550-021-00082-1.
DOI: https://doi.org/10.1186/s40550-021-00082-1

Interpretive Summary: Salmonella and Escherichia coli O157 are two foodborne pathogens that cause self-limiting intestinal infections in healthy individuals. However, in people with underlying conditions, children and the elderly, they cause severe illnesses requiring antibiotic therapy. Cattle are important reservoirs by carrying these pathogens in their intestines, and beef is the main source of infections in humans. Beef can be contaminated during slaughtering process through the transfer of the pathogens from the intestinal content or the hide onto the carcass. In this study, we assessed the presence of these two bacteria in the feces, hides and carcass of beef cattle at two slaughterhouses in Ethiopia. Salmonella was detected at equal proportions (7.1%) in the feces and hide swabs, and in 8.6% of the carcass swabs. E. coli O157 was detected in 8.6% of the fecal samples, in 4.3% of the hide and 7.1% of the carcass swabs. Salmonella isolates from the feces and carcass swab of two animals, and E. coli O157 isolates from the hide and carcass swabs of one animal had similar genetic profiles showing the possible transfer of the pathogens onto the carcass from intestinal contents and hides. The study indicates other sources such as cross-contamination from equipment could be responsible for the carcass contamination. Out of the 16 Salmonella isolates detected, 10 of them belong to two serotypes that cause severe systemic infections in humans, requiring antimicrobial therapy. These two serotypes were also multidrug resistant or resistant to last resort drugs to treat such infections. The results indicate that cross contamination through the equipment may be an important source of carcass contamination at beef processing plants.

Technical Abstract: 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. 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 in 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 might be positive due to 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. The results indicated that cross contamination may be an important source for carcass contamination.