Prevalence, characterization and clonal analysis of Escherichia coli O157 non-H7 serotypes that carry eae alleles

Authors: FENG, PETER - Us Food & Drug Administration (FDA); KEYS, CHRISTINE - Us Food & Drug Administration (FDA); LACHER, DAVID - Us Food & Drug Administration (FDA); MONDAY, STEVEN - Us Food & Drug Administration (FDA); Shelton, Daniel; ROZAND, CHRISTINE - University Of Lyon; RIVAS, MARTA - National Laboratories And Institutes Of Health (ANLIS); WHITTAM, THOMAS - Michigan State University

Submitted to: FEMS Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2010
Publication Date: 7/10/2010
Citation: Feng, P., Keys, C., Lacher, D., Monday, S., Shelton, D.R., Rozand, C., Rivas, M., Whittam, T. 2010. Prevalence, characterization and clonal analysis of Escherichia coli O157 non-H7 serotypes that carry eae alleles. FEMS Microbiology Letters. 308(1):62-67.

Interpretive Summary: E. coli O157:H7 has been responsible for several food-borne outbreaks in recent years, resulting in numerous hospitalizations and a few fatalities. Consequently, food is routinely tested for the presence of this bacterium. Many tests utilize antibodies that recognize specific cell surface molecules corresponding to the designation “O157”. However, not all E. coli O157 are the same; O157 non-H7 strains are typically much less pathogenic than O157:H7 strains. The present study was undertaken to characterize and compare several O157 non-H7 strains isolated from water, meat and clinical samples from the U.S., France, and Argentina. Although most strains from different sources and countries were unique, the strains isolated from water in the U.S. and from meat in France were essentially identical. These results emphasize the fact that not all E. coli O157 are necessarily pathogenic and that confirmatory testing should be conducted to ensure that any O157 strains detected in foods are indeed the pathogenic E. coli O157:H7. These findings are particularly relevant to the produce industry, testing companies, and regulatory agencies

Technical Abstract: We characterized nineteen O157 non-H7 strains that were isolated from food, water, and both symptomatic and asymptomatic patients in various countries. All the isolates were serologically and genetically confirmed to be O157 non-H7 strains, but could not be H serotyped. None of the strains had trait O157:H7 virulence factors, including shiga toxins, enterohemolysin, gamma'eae' allele and the +93 uidA SNP. However, 15/19 strains carried other eae alleles, including alpha, beta, epsilon and kappa/delta. Genotypic H-typing showed that the alpha-eae bearing strain was [h45], beta- and epsilon'eae strains were [h16] and kappa/delta-eae strains were [h39]. PFGE profiles of the beta''and epsilon'eae bearing O157:[h16] strains shared similarities, but less so with [h16] strains that did not carry eae. Interestingly, the epsilon'eae bearing O157:[h16] strains from meat samples in France shared great similarity in profiles to the O157:[h16] strains from water in the U.S. Multilocus sequence typing showed that all the eae-bearing O157:[h16] had ST-171, a common sequence type that is distant to the EHEC clonal groups and had previously not included any strains from the O157 serogroup.