Shiga toxin-producing Escherichia coli (STEC) are regularly implicated in foodborne illness outbreaks and
recalls of ground beef. In this study we determined the High Pressure Processing (HPP) D10 value (the
processing conditions needed to reduce the microbial population by 1 log) of 39 STEC isolates, including
the “big six” serovars, O104 and O157:H7. STEC isolates included those isolated from animals and
environmental sources in addition to those associated with illness in humans. Individual STEC were
inoculated into 80% lean ground beef and treated with HPP (350 MPa, 4 C, up to 40 min). The mean D10
was 9.74 min, with a range of 0.89e25.70 min. The D10 of the STEC involved in human illness was 9.25 vs.
10.40 min for those not involved in human illness (p > 0.05). The presence or absence of genes encoding
virulence factors (e.g. Shiga toxin 1 or 2, intimin, or enterohemolysin) had no effect on the HPP D10
(p > 0.05). The high D10 of some STEC involved in human illness should be considered in selecting HPP
processing parameters for ground beef. This study demonstrates the heterogeneity of STEC resistance to
HPP. Risk assessors and the food industry can use this information to provide safer meat products to
consumers.