Eblen states that it is difficult to distinguish pathogenic non-O157 STEC strains from non-pathogenic E. coli because the former rarely posses any distinguishing phenotypic or biochemical characteristics from the latter. The lack of reliable and validated laboratory methods for testing various food matrices has meant that food is not routinely tested for non-O157 STEC. She suggests that further research is needed to support new and better targeted detection methods.
When O157 seemed to be the obvious cause for most contaminations, the non-O157 types just weren’t considered-nor were labs set up for them. According to a 2003 paper entitled, “Non-O157 Verotoxin-Producing Escherichia coli: A Problem, Paradox, and Paradigm,” authored by Karl A. Betteleheim (Society for Experimental Biology and Medicine), the testing media was designed for isolation of O157:H7 because the large number of outbreaks of human illness were attributed to this serotype. Thus, many labs around the world have screening of human or animal feces limited to O157:H7. However, according to Bettleheim, there are more than 60 STEC serotypes that have been associated with human illnesses.