Development and validation of intervention strategies to control Escherichia coli O157:H7 and Salmonella Typhimurium Dt 104 in needle tenderized and injected beef (USDA choice strip loins - longissimus lumborum) under two simulated industrial conditions

After investigation by state health departments and the Center for Disease Control and Prevention, three different outbreaks between 2000 and 2004 were linked to the consumption of non-intact products contaminated with Escherichia coli O157:H7. Following this, in May 2005, the USDA-FSIS published notice that establishments who produce mechanically tenderized and moisture enhanced beef products were required to reassess their HACCP plans due potential contamination risk to consumers. The purpose of this study was to determine the effectiveness of different intervention strategies to control E. coli O157:H7 and Salmonella enterica serotype Typhimurium definitive phage type 104 in needle tenderized and enhanced beef strip loins. Treatments included a) lactic acid producing bacteria (LAB; ~107 cfu/g), acidified sodium chlorite (ASC; 1000 ppm), and lactic acid (LA; 3%) which were evaluated under two application scenarios: packer and purveyor. Packer samples were treated immediately after fabrication, whereas purveyor samples were treated after aging. Samples were aged for 14 or 21 days prior to needle tenderization or enhancement followed by microbial enumeration on the surface and at two internal subsections within the product.

Salmonella and E. coli O157:H7 were significantly reduced by all interventions upon initial application. At the packer setting, Salmonella surface counts on day 14 were significantly reduced by all interventions in enhanced and needle tenderized beef. On day 21 all interventions were significantly effective in reducing pathogen levels in needle tenderized beef; however, only LAB and LA were significant in enhanced samples. At the purveyor setting, Salmonella surface counts on day 14 were significantly reduced by LA (needle tenderized beef) and LAB (enhanced beef). At the purveyor setting no differences between interventions were observed on day 21. E. coli O157:H7 surface counts at the packer setting were significantly reduced in needle tenderized beef on day 14 by the application of LA; however, no differences were observed on enhanced samples. On day 21 all interventions were significantly effective in reducing pathogen counts. At the purveyor setting, E. coli O157:H7 was reduced significantly from needle tenderized and enhanced beef only by application of LAB (Day 14 and 21).

Internal E. coli O157:H7 counts were significantly reduced by 90% or more by using LAB, LA and ASC. A > 2 log reduction in the E. coli O157:H7 counts were observed after treatment with the interventions on day 14 in needle tenderized and injected beef. On day 21, ASC and LA reduced E. coli O157:H7 by up to 3 logs while LAB showed 2.0 log reductions. Internal Salmonella counts were reduced by > 2.0 log after 14 days using LAB and LA, and were significantly reduced by all interventions by day 21 of aging.

Results from this study indicate that application of LAB, ASC, and LA sprays reduced E. coli O157:H7 and Salmonella enterica serotype Typhimurium definitive phage type 104 in beef subprimals with varying degrees of efficacy depending on time, location, and application setting.