Escherichia coli O157:H7

One of the main food safety issues concerns the rise of a bacteria which can damage kidneys and cause severe illness if not death. Escherichia coli O157:H7, is a Gram-negative rod, which was first identified in 1982 and is one of the predominant enterohaemorrhagic serotypes for E. coli. It is also called enterohaemorrhagic E. coli (EHEC).

In 1982, it was associated with two major food related outbreaks concerning the consumption of undercooked ground beef. Haemorrhagic colitis was seen in 26 cases in Oregon and 21 cases in Michigan which caused consternation because of the nature of complaint (Riley et al., 1983; Wells et al., 1983).

The range of illnesses it causes are varied. It is the most common cause of hemolytic uremic syndrome (HUS) (Siegler, 1995; Kim et al., 2016) and by implication the leading cause of kidney failure in children and the elderly in the United States (Boyce et al., 1995). It also causes haemorrhagic colitis characterised by water diarrhea at first and becoming bloody diarrhea with thrombotic thrombocytopenic purpura (TTP). Generally, the situation lasts between 2 and 9 days (Doyle, 1991). 


E.coli  pathogenic types have been isolated from animals, such as cattle, deer, sheep, goats, horses, dogs, as well as birds, and flies (Griffin & Tauxe, 1991; Chapman et al., 1997; Hancock et al., (1998)

Health Issues

It emerged as a health concern in 1992 when it was linked to extremely bloody diarrhoea (Riley et al., 1983; Griffin and Tauxe, 1991). Estimated deaths that were recorded up to the last century numbered 61 in the USA alone in a total case number of 73,500 (Mead et al., 1999). That figure has apparently risen as the range of fresh food products has increased. The pathogenicity is caused by production and release of hemolysin and Shiga-type toxins. E.coli O157:H7’s growth range is almost on a par with that other important food borne pathogen, Listeria. It grows between 7 and 50 °C which makes it a mesotrophic bacteria, and grows readily in acidic foods, just above pH 4.4 with a minimum water activity (aw) of 0.95 (WHO, 2011).

Lettuce leaves. Photo by SOMMAI. Courtesy of
Lettuce leaves. Photo by SOMMAI. Courtesy of

Foods susceptible to E.coli growth and passed to humans through ingestion include mainly contaminated raw and undercooked dairy and meat products. The EFSA (European Food Safety Authority) found that consumption of contaminated cheese for example caused 0.4% of total food related diseases in 2006 (EFSA, 2008). One of the biggest issues in recent times has been contamination of fresh and freshly-cut salad leaves (Rangel et al., 2005; Delaquis et al., 2007; Söderström et al., 2008; Lynch et al., 2009; US FDA 2009). Lettuce by virtue of the amount consumer has been implicated in a number of outbreaks (Yang et al., 2012). Hypochlorite washing and disinfection is a common method for treating both the salad and the internal surfaces of the packaging. However, it has not been sufficient enough in some recorded cases where fresh food has been concerned (Pérez Rodríguez et al., 2011). Ensuring foods are not cross-contaminated by practising good hygiene and presenting hurdles to hinder bacterial growth is essential.


Boyce, T.G., Swerdlow, D.L., Griffin, P.M. (1995) Current concepts: Escherichia coliO157:H7 and the hemolytic uremic syndrome. New Engl. J. Med. 333 pp. 364–8.

Chapman, P.A., Siddons, C.A., Gerdan Malo, A.T., Harkin, M.A. (1997) A 1-year study of Escherichia coli O157 in cattle, sheep, pigs and poultry. Epidemiol. Infect. 119 pp. 24550.

Delaquis, P., Bach, S., Dinu, L.D. (2007) Behavior of Escherichia coli O157:H7 in leafy vegetables. J. Food Prot. 70 pp. 1966–74

Doyle, M.P. (1991) Escherichia coli O157:H7 and its significance in foods. Intl. J. Food Microbiol. 12 pp. 289301.

European Food Safety Authority (EFSA). 2008. Zoonoses data collection reports. Available at: (Accessed on February 21st, 2012).

Griffin, P.M., Tauxe, R.V. (1991) The epidemiology of infections caused by Escherichia coli O157:H7, other enterohemorrhagic E. coli, and the associated hemolytic uremic syndrome. Epidemiol. Rev. 13 pp. 60–98

Hancock, D.D., Besser, T.E., Rice, D.H., Ebel, E.D., Herriott, D.E., Carpenter, L.V. (1998) Multiple sources of Escherichia coli O157 in feed lots and dairy farms in the northwestern United States. Prevent. Vet. Med. 35 pp. 119.

Kim, G.H., Fratamico, P., Breidt, F., Oh, D.H. (2016) Survival and expression of acid resistance genes in Shiga toxin-producing Escherichia coli acid adapted in pineapple juice and exposed to synthetic gastric fluid. J. Appl. Microbiol. 121(5) pp. 141626.

Lynch, M.F., Tauxe, R.V., Hedberg, C.W. (2009) The growing burden of foodborne outbreaks due to contaminated fresh produce: risks and opportunities. Epidemiol. Infect. 137 pp. 307–15.

Mead, P.S., Slutsker, L., Dietz, V., McCaig, L.F., Bresee, J.S., Shapiro, C., et al. (1999) Food-related illness and death in the United States. Emerg. Infect. Dis. 5 pp. 607–25.

Rangel, J.M., Sparling, P.H., Crowe, C., Griffin, P.M., Swerdlow, D.L. (2005) Epidemiology of Escherichia coli O157: H7 outbreaks, United States, 1982–2002. Emerg. Infect. Dis. 11 pp. 603–9.

Riley, L.W., Remis, R.S., Helgerson, S.D., McGee, H.B., Wells, J.G., Davis, B.R., et al. (1983) Hemorrhagic colitis associated with a rare Escherichia coli serotype. New Engl. J. Med. 308 pp. 681–5

Schmidt, J.W., Bosilevac, J.M., Kalchayanand, N., Wang, R., Wheeler, T.L., Koohmaraie, M. (2014) Immersion in antimicrobial solutions reduces Salmonella enterica and Shigatoxin-producing Escherichia coli on beef cheek meat. J. Food Prot. 77(4) pp. 53848

Siegler, R.L. (1995) The hemolytic uremic syndrome. Pediatr. Clin. North Am. 42 pp. 150529.

Söderström, A., Osterberg, P., Lindqvist, A., Jönsson, B., Lindberg, A., Blide Ulander, S., et al. (2008) A large E. coli O157 outbreak in Sweden associated with locally produced lettuce. Foodborne Pathog. Dis. 5  pp. 339–49.

USA FDA. (2009) Guidance for industry: Guide to minimize microbial food safety hazards of leafy greens. Available from: Accessed August 3rd, 2014).

Wells, J.G., Davis, B.R., Wachsmuth, I.K., Riley, L.W., Remis, R.S., Sokolow, R., Morris, G.K. (1983) Laboratory investigation of haemorrhagic colitis outbreaks associated with a rare Escherichia serotype. J. Clin. Microbiol. 18 pp. 51220.

World Health Organization (WHO). (2011) Enterohaemorrhagic Escherichia coli (EHEC), Fact sheet N°125. Available at: (Accessed February 21st, 2012).

Yang, Y., Luo, Y., Millner, P., Turner, E., Feng, H. (2012) Assessment of Escherichia coli O157:H7 transference from soil to iceberg lettuce via a contaminated field coring harvesting knife. Int. J. Food Microbiol. 153 pp. 345–50.

1 Comment

  1. hey buddy – if you think eating lettuce is bad enough just try eating a melon. I reckon it is a death sentance for anyone at the moment given what we have to put up with. I go to my local in nursery where they sell some of the best melons around – it is at least grown on site and I know they don’t put a load of crap on them.

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