Identification of bovine reservoirs of human pathogenic non-O157 Shiga toxin-producing E. coli

This project determined the prevalence, level, and types of O157 and non-O157 Shiga toxin-producing E. coli (STEC) in cattle from different production systems.

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Objectives

To determine the prevalence, level, and types of O157 and non-O157 Enterohemorrhagic E. coli (EHEC) in cattle based on analysis of rectal anal mucosa swabs (RAMS) collected at harvest from cattle originating from different production systems.

Conclusions

Overall, EHEC-O26 was most frequent in eastern dairy cattle (16.8%), while EHEC-O45 was more widely spread in central fed cattle (21.2%), eastern fed (25.2%) and cull dairy cattle (28.1%), and northern fed (22.3%) and cull beef cattle (28.7%).  EHEC-O103 was most common in northern fed cattle (32.2%), but also frequent in central (22.3%), western (21.7%) and southern (19.5%) fed cattle.  EHEC-O111 was most common in southern cull beef (3.4%) and fed (2.0%) cattle and eastern cull beef (2.4%) and cull dairy (2.3%) cattle.  Finally EHEC-O145 was most commonly identified in northern cull beef cattle (12.0%).  EHEC-O121 was the least frequent (0.3%) but identified in all regions except the north and identified in all cattle types at least once.  Only samples that were culture confirmed to contain an EHEC were enumerated.  Across all regions, the fed cattle had the highest percentage of EHEC super shedding, >10⁵ CFUs/RAMS, followed by cull dairy and then cull beef cattle.  Within each log range of CFUs/RAMS (i.e.: 10⁵,10⁶, 10⁷ etc…) the proportion of shedding was similar amongst the production groups.  The most commonly identified EHEC shed at high levels were EHEC-O157 (23.9%), EHEC of non-top-7 O-groups (19.7%), EHEC-O103 (18.5%), and EHEC-O26 (12.6%), while other EHEC-O111, O145, O45 and O121 were identified as being shed less often, 5.9%, 2.9%, 0.8%, and 0.4% respectively.

Deliverable

The results will assist the meat industry, regulators and public health officers by identifying the particular EHEC serogroups that are more commonly associated with different types of cattle, allowing more targeted and efficient testing and intervention use.  As well as offer information on the levels of EHEC shed by different groups of cattle.