Evidence of Non-O157 Shiga Toxin-producing Escherichia coli in the Feces of Meat Goats at a U.S. Slaughter Plant

Introduction: Shiga toxin-producing Escherichia coli (STEC) are important human pathogens and attention to non-O157 serogroups has increased in recent years.  Although cattle are normally considered the primary reservoir for STEC, recent illnesses associated with goat contact has demonstrated the importance of these animals as reservoirs for the organisms.  However, the prevalence of STEC, including non-O157 serotypes, in U.S. goats has not been well described.  

Purpose: Our objectives were to determine the prevalence of six major non-O157 STEC serogroups in the feces of meat goats at slaughter in the southeastern U.S. 

Methods: Rectal contents from 296 goats were collected post-evisceration over nine days between August and October.  Samples were enriched in Escherichia coli broth and incubated for six hours at 40ºC.  After enrichment, DNA was extracted and used as template in an 11-gene multiplex PCR that detects major non-O157 serogroups (O26, O45, O103, O121, O111, and O145) and virulence genes.  Samples were considered positive when at least one non-O157 STEC serogroup was present with either stx1 or stx2, the Shiga toxin-producing genes.  

Results: All six non-O157 serogroups were detected by PCR in our samples.  Prevalence of O26 was highest with 6.4% of rectal contents positive.  The prevalence of O45 was 3.4%, O103 was 4.4%, O111 was 4.1%, O121 was 1.4% and O145 was 3.0%.  Twenty-two of 296 samples (7.4%) had more than one non-O157 serogroup present.  One sample had three non-O157 STEC serogroups.  Twenty-four samples (8.1%) were PCR positive for a non-O157 serogroup, but lacked stx1 or stx2.

Significance: Goats appear to be an important reservoir for non-O157 STEC and further work to understand the characteristics, epidemiology and ecology of STEC in these animals is warranted.