Escherichia coli are Gram-negative, rod-shaped bacteria which are found in the lower intestine within humans and animals. These enteric species are a normal part of the digestive system, preventing the growth of pathogenic organisms. Although most strains of E. coli are harmless, some strains can cause gastrointestinal illnesses and other complications such as kidney failure.
Non-O157:H7 STEC (Shiga toxin-producing E. coli) – including E. coli O145 – is a pathogenic group of E. coli. Non O157:H7 STEC causes illnesses similar to those triggered by O157:H7 STEC due to production of Shiga toxin. Although most reported STEC cases are caused by O157:H7, a large number of non-O157 cases are often misdiagnosed or unreported due to poor identification methods and epidemiological surveillance.
Approximately 265,000 STEC cases occur in the US each year, with non-O157 STEC estimated to account for 75% of these infections. Children, the elderly and people with compromised immune systems are particularly at risk, which in some cases can be life-threatening. Symptoms include diarrhoea (often bloody) and vomiting which can occur 1-10 days after exposure. Non-O157 STEC, like Shigella, produce Shiga toxin which can cause extra intestinal complications such as haemorrhagic colitis and haemolytic uremic syndrome (HUS), which is a type of kidney failure. HUS develops in 5-10% of those infected with STEC. The duration of illness is typically 5-10 days; HUS can develop after one week of symptoms.
The infective dose of O157 and O111 STEC is low, at 10-100 organisms, but the infective dose of other serotypes remains unknown.
Non-O157 STEC bacteria are transmitted via the faecal-oral route; consumption of contaminated foods such as soft cheeses, unpasteurised milk, undercooked meat and raw vegetables can result in illness. Other sources of infection include the consumption of untreated water, swimming in contaminated lakes and contact with cattle.
- United States Food and Drug Administration. Bad Bug Book: Foodborne pathogenic microorganisms and natural toxins handbook
- Food Safety.gov
- Centers for Disease Control and Prevention: Escherichia coli (E. coli)
- National Center for Biotechnology Information: Non-O157 Shiga toxin-producing Escherichia coli infections in the United States, 1983-2002
- Recommendations for diagnosis of Shiga Toxin-producing Escherichia coli infections by clinical laboratories. http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5812a1.htm
Learn more about other common and less common food bugs in our series of Thermo Scientific Application Notes, some of which are available to download as PDFs. Alternately, visit our food document library.