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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Produce Safety and Microbiology Research » Research » Publications at this Location » Publication #310791

Research Project: Biology and Control of Human Pathogens on Fresh Produce

Location: Produce Safety and Microbiology Research

Title: High genotypic and phenotypic similarity among Shiga toxin-producing Escherichia coli O111 environmental and outbreak strains

Author
item Diodati, Michelle
item Bates, Anne
item Cooley, Michael - Mike
item Walker, Samarpita
item Mandrell, Robert - Former ARS Employee
item Brandl, Maria

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2014
Publication Date: 3/12/2015
Publication URL: http://online.liebertpub.com/doi/10.1089/fpd.2014.1887
Citation: Diodati, M.E., Bates, A.H., Cooley, M.B., Walker, S., Mandrell, R., Brandl, M. 2015. High genotype and phenotypic similarity among Shiga toxin-producing Escherichia coli O111 environmental and outbreak strains. Foodborne Pathogens and Disease. 12:235-243.

Interpretive Summary: E. coli serogroup O111 is among the six most commonly reported non-O157:H7 Shiga toxin-producing Escherichia coli (STEC), which are emerging foodborne pathogens that have caused numerous outbreaks and sporadic cases of enteric illness in industrialized countries We have assembled a collection of environmental and clinical strains of STEC O111 from diverse sources and investigated various genotypic and phenotypic characteristics of these strains to gain a better understanding of the epidemiology and biology of this important serogroup. Phylogenetic analysis revealed a cluster of strains with high similarity comprised of strains from environmental, outbreak and sporadic illness origins, despite overall large genotypic diversity among the collection. A distinct aggregative behavior was observed in the cultures of environmental and outbreak strains, but not in those of sporadic case strains. Our results indicate that STEC O111 that share high genotypic similarity and phenotypic traits with outbreak strains are carried in the agricultural environment, and may increase the risk of food-borne disease.

Technical Abstract: E. coli serogroup O111 is among the six most commonly reported non-O157:H7 Shiga toxin-producing Escherichia coli (STEC), which are emerging foodborne pathogens that have caused numerous outbreaks and sporadic cases of enteric illness in industrialized countries. We have assembled a collection of environmental and clinical strains of STEC O111 from diverse sources and investigated various genotypic and phenotypic characteristics of these strains to gain a better understanding of the epidemiology and biology of this important serogroup. 63% of the strains (24/38) were of H-type 8, which dominated the environmental and outbreak strains group, whereas the sporadic clinical strains were more heterogeneous in H-type. All strains harbored the Shiga toxin 1 gene and several strains, including the environmental strains, also carried the Shiga toxin 2 gene. PFGE analysis of XbaI profiles revealed a cluster of strains with high phylogenetic similarity comprised of strains from environmental, outbreak and sporadic illness origins, despite overall large genotypic diversity among the collection. A distinct aggregative behavior was observed in the cultures of environmental and outbreak strains, but not in those of sporadic case strains. Among environmental and outbreaks strains, aggregation was correlated positively with production of curli fimbriae and RpoS function, and negatively with cellulose synthesis, while the non-aggregative behavior of sporadic case strains correlated (positively) only with cellulose production. Our results indicate that STEC O111 that share high genotypic similarity and phenotypic traits with outbreak strains are carried in the agricultural environment, and may increase the risk of food-borne disease.