title: Translocation of surface-inoculated Escherichia coli O157:H7 into beef subprimals following blade tenderization.
abstract: In phase I, beef subprimals were inoculated on the lean side with ca. 0.5 to 3.5 log CFU/g of a rifampin-resistant (rifr) cocktail of Escherichia coli O157:H7 and passed once, lean side up, through a mechanical blade tenderizer. Inoculated subprimals that were not tenderized served as controls. Ten core samples were removed from each subprimal and cut into six consecutive segments: segments 1 to 4 comprised the top 4 cm and segments 5 and 6 the deepest 4 cm. Levels of E. coli O157:H7 recovered from segment 1 of control subprimals when inoculated with ca. 0.5, 1.5, 2.5, or 3.5 log CFU/g were 0.6, 1.46, 2.5, and 3.19 log CFU/g, respectively. Following tenderization, pathogen levels recovered from segment 1 inoculated with 0.5 to 3.5 log CFU/g were 0.22, 1.06, 2.04, and 2.7 log CFU/g, respectively. Levels recovered in segment 2 were 7- to 34-fold lower than levels recovered from segment 1. Next, in phase II, the translocation of ca. 4 log CFU of the pathogen per g was assessed for lean-side-inoculated subprimals passed either once (LS) or twice (LD) through the tenderizer and for fat-side-inoculated subprimals passed either once (FS) or twice (FD) through the tenderizer. Levels in segment 1 for LS, LD, FS, and FD tenderized subprimals were 3.63, 3.52, 2.85, and 3.55 log CFU/g, respectively. The levels recovered in segment 2 were 14- to 50-fold lower than levels recovered in segment 1 for LS, LD, FS, and FD subprimals. Thus, blade tenderization transfers E. coli O157:H7 primarily into the topmost 1 cm, but also into the deeper tissues of beef subprimals.
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, Microbial Food Safety Research Unit, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA. john.luchansky@ars.usda.gov
authors.forename: J B
authors.initials: JB
authors.lastname: Luchansky
authors.forename: R K
authors.initials: RK
authors.lastname: Phebus
authors.forename: H
authors.initials: H
authors.lastname: Thippareddi
authors.forename: J E
authors.initials: JE
authors.lastname: Call
mesh_terms: D000818:Animals; D002417:Cattle; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004866:Equipment Contamination; D019453:Escherichia coli O157 / Q000254:growth & development / Q000502:physiology*; D005506:Food Contamination / Q000032:analysis* / Q000517:prevention & control; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D006801:Humans; D008460:Meat / Q000382:microbiology*