Do Pre-harvest Interventions Intended for E. coli O157:H7 Affect Fecal Shedding of Non-O157 STEC or Salmonella in Feedlot Cattle?

Shiga toxin-producing Escherichia coli (STEC) and Salmonella are food safety issues
that can have significant negative ramifications for the beef industry. Recently, the US
Department of Agriculture, Food Safety and Inspection Service (FSIS) declared six non-O157
STEC serogroups as adulterants in ground meat and non-intact beef products, which is extremely
concerning given the tremendous gaps in scientific knowledge. In recent years, there is also
growing concern regarding Salmonella in beef production systems. If beef producers are to
integrate pre-harvest interventions for controlling STEC and/or Salmonella, there is a need to
determine the efficacy of interventions and whether there are any unintended consequences
(positive or negative) when used in commercial production systems. <P>

The objectives of the current research were to: 1) Determine whether commercially
available pre-harvest interventions (vaccine and direct-fed microbial) that were used to reduce
STEC O157 in feces of feedlot cattle had any effects on fecal shedding of non-O157 STEC
(O26, O45, O103, O111, O121, O145) or Salmonella, and 2) Determine if the presence of STEC
O serogroup-specific genes within a cattle fecal sample was associated (decrease, increase or no
difference) with the presence of other STEC O serogroups or Salmonella within the cattle feces.