E. coli O157:H7 vs. non-O157 STEC, What’s the Difference?
Escherichia coli (E. coli) is the name of an expansive species of bacteria. Today, researchers have identified over 700 serotypes of E. coli. Surprisingly, most types of E. coli are not harmful to humans or animals and can be found naturally in soil, water, food, and human intestines. In fact, certain types of E. coli can actually assist in human digestion. STEC is most commonly linked with human gastrointestinal illness, though not always. Current research shows that the production of Shiga toxins does not necessarily render E. coli pathogenic, rather, certain combinations of virulence factor genes, including various types and expressions of bacteriophages, plasmids, pathogenicity islands, and O-islands.
In just 2019, there were 5 multistate E. coli outbreaks in the U.S. of various pathogenic strains of E.coli. E. coli O157:H7 is known as the most prominent type of STEC causing foodborne illness in the U.S. However, recent research has taken a turn increasingly towards the study of non-O157 STEC, which have been largely overlooked in the early research of E. coli. The current research shows that non-O157 STEC can cause human illness as well. One study estimates the E. coli O157:H7 accounts for nearly two-thirds of the cases of E. coli related foodborne illness, with non-O157 STEC accounting for the remaining one-third of cases. However, even this report is biased towards the prevalence of E. coli O157:H7 over non-O157 STEC, due to several of the reporting clinics used for the study only screening for E. coli O157:H7.
According to Ron Simon and Associates, a leader in National food safety litigation, there are currently three common virulent non-O157:H7 E. coli groups. These are STEC serogroups O26, O111, and O103. Research regarding non-O157 STEC remains limited, due to the difficulty to detect these serogroups through current E. coli testing methods. Although, on average non-O157:H7 E. coli are less likely to cause severe illness, some serogroups have been discovered to cause the most severe forms of illness. The relative prevalence and severity of E. coli outbreaks prove there is a necessity for further investigation regarding prevention and treatment of non-O157 STEC E. coli, as well as E. coli O157:H7.