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United States Department of Agriculture

Agricultural Research Service

Title: Efficacy of Using a Sponge Sampling Method to Recover Low Levels of Escherichia Coli O157:h7, Salmonella Typhimurium, and Aerobic Bacteria Frombeef Carcass Surface Tissue

Authors
item Dorsa, Warren
item Siragusa, Gregory
item Cutter, Catherine
item Berry, Elaine
item Koohmaraie, Mohammad

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 23, 1996
Publication Date: N/A

Interpretive Summary: Recovery of total bacteria as well as low levels of E. coli O157:H7 and Salmonella from beef carcasses was determined by sponge (a moist sponge was used to wipe the carcass surface) and excision (a sterile knife was used to cut the sample from the beef carcass) sampling in three separate studies. For the first study, samples were taken from three points on the processing line: 1) before the carcass was washed, 2) after the carcass was washed, and 3) after the carcass was in the chill cooler for 24 hours. Sponge sampling recovered fewer total bacteria from beef carcasses than excision; however, the difference between excision and sponging was similar at all sampled process points. Both sampling methods recovered higher levels of total bacteria from carcasses after a 24-h chill period. Both methods also recovered low levels of E. coli and coliforms on beef carcasses. In the second study, both sponging and excision recovered E. coli O157:H7 and Salmonella from beef carcass surfaces when present at a level of approximately one bacteria per 100 square centimeters. Recoveries from beef before it was chilled and after being chilled for 24 hours were similar for both sponging and excision. A third study demonstrated that the freezing and storage of sponge samples up to 8 days significantly decreased recovery of low levels of Salmonella from beef carcass surfaces. Sponge sampling appears to be an adequate sampling method for recovery of low levels of these bacteria from surfaces of beef carcasses regardless of location within the slaughter process.

Technical Abstract: Recovery of aerobic bacterial populations as well as low levels of Escherichia coli O157:H7 and Salmonella typhimurium from beef carcasses was determined by sponge (SP) and excision (EX) sampling in 3 separate studies. For the first study, samples were taken from 3 points on the processing line: 1) pre-wash, 2) post-wash, and 3) after 24 h in the chill cooler. Sponge sampling recovered fewer total aerobic bacteria from beef carcasses on a processing line than EX; however, the difference between EX and SP was similar at all sampled process points. Both sampling methods recovered higher levels of total aerobic bacteria from carcasses after a 24-h chill period. Both methods also recovered low levels of E. coli and coliforms on beef carcasses. In the second study, both SP and EX recovered antibiotic-marked strains of E. coli O157:H7 and Salmonella typhimurium from beef carcass tissue surface at an inoculation level of approximately 1 CFU/100 cm**2. Recoveries from pre- or post-24-h chilled tissue were similar for both SP and EX. Sponge sampling appears to be an adequate sampling method for recovery of low levels of pathogens from surfaces of beef carcasses regardless of location within the process. However, a third study demonstrated that the freezing and storage of SP samples at -20 deg C significantly decreased recovery of S. typhimurium from beef tissue when present at low levels (</= 10 CFU/100 cm**2).

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