Enterohaemorrhagic strains of Escherichia coli as a paradigm of emerging pathogens. Lessons from the large outbreak of foodborne infections centred in Germany throughout May and June of 2011

Enterohaemorrhagic strains of Escherichia coli (EHEC) are foodborne zoonotic pathogens associated with major outbreaks and sporadic cases of diarrhoea and haemorrhagic colitis or bloody diarrhea, which can progress to the hemolytic uremic syndrome (HUS). The importance of EHEC lies in the severity of HUS, which is the most frequent cause of acute renal failure in children in the Americas and Europe. It was predicted years ago that EHEC strains other than the prototypic O157H7 serotype would emerge as significant foodborne pathogens. Since then, these microorganisms have been linked to numerous outbreaks and sporadic cases of disease around the world. The incidence of these serotypes continues to grow, which means they can be considered emerging pathogens. A recent example is the large outbreak of foodborne infections caused by EHEC O104H4, which was mainly centred in Germany lasting throughout May and June of 2011. The outbreak strain shows a combination of virulence factors from different E. coli pathotypes, highlighting the way in which the plasticity of bacterial genomes facilitates the emergence of new highly virulent pathogens. Epidemiologic investigations traced the origin of the outbreak to fenugreek seeds imported from Egypt in 2009. The international dimension of the outbreak illustrated the urgent need for improving the epidemiologic surveillance of EHEC. ©2012 Ediciones Mayo, S.A. All rights reserved.