Prevalence and characteristics of intimin-producing Escherichia coli strains isolated from healthy chickens in Korea

Abstract

Virulent Escherichia coli strains have commonly been associated with diarrheal illness in humans and animals. Typical enteropathogenic Escherichia coli (EPEC) with intimin gene (eaeA) and E. coli adherence factor plasmid, or atypical EPEC with only eaeA have been implicated in human cases. In the present study, we investigated the prevalence of virulence-associated genes including eaeA in the E. coli strains isolated from cloacal specimens of 184 chicken flocks in 7 provinces in Korea between 2009 and 2010. When 7 virulence genes (VT1, VT2, LT, and ST for enterotoxigenic E. coli; eaeA and bfpA for enteropathogenic E. coli; and aggR for enteroaggregative E. coli) were screened by multiplex PCR, a total of 30 E. coli strains carrying only the eaeA gene were detected from 184 flocks that were identified as atypical enteropathogenic Escherichia coli (aEPEC). The aEPEC strains were analyzed by eae subtyping, phylogenetic grouping PCR, and serotyping. Twelve (40%) of 30 aEPEC strains possessed an eae-β subtype, followed by θ (30%), ε (16.7%), and β1 (13.3%). Eight (26.7%) of 30 aEPEC strains were designated into the phylogenetic group A. Two (6.7%) and 3 (10%) aEPEC strains were classified into the phylogenetic group B2 and D, respectively. A total of 15 (50%) aEPEC strains were serotyped to groups O24, O25, O26, O71, O80, O103, and O157, and the remaining strains were nontypeable. In analyzing the genetic diversity among the 30 aEPEC isolates by the pulsed-field gel electrophoresis method with XbaI-digestion, the pulsed-field gel electrophoresis profiling produced 20 different patterns, but isolates within the same group did not show clear geographic or breed relationships. Our data indicate that healthy chickens may constitute an important natural reservoir of aEPEC strains, and suggest that transmission to humans could not be excluded.

Antimicrobial resistance profiles and virulence factors of Escherichia coliO157 collected from a poultry processing plant*

“…Intimin is required for human and animal intestinal mucosal colonization of enterohemorrhagic E. coli (7,22,23). According to our mPCR results, 10 (77%) of the 13 isolates had only the eaeA gene (intimin).…”

Host Range-Associated Clustering Based on Multilocus Variable-Number Tandem-Repeat Analysis, Phylotypes, and Virulence Genes of Atypical Enteropathogenic Escherichia coli Strains

“…EPEC is highly prevalent (63%) in poultry fecal samples according to our previous report, compared with other domestic animals (23). A group of researchers from South Korea (24) and Argentina (25) isolated aEPEC from poultry. The South Korea group described the phylogenetic groups, intimin types, and serotypes, while the Argentina group described the serotypes and intimin types of the isolated strains and claimed that the strains could be diarrheagenic to humans, although they did not screen the virulence genes among the isolated strains, which is helpful to determine whether the strains are diarrheagenic (10).…”

Specific Properties of Enteropathogenic Escherichia coli Isolates from Diarrheal Patients and Comparison to Strains from Foods and Fecal Specimens from Cattle, Swine, and Healthy Carriers in Osaka City, Japan

“…Humans also appear to be a reservoir of the aEPEC possessing these intimin types in Japan. However, avian pathogenic E. coli (APEC) possessing eae is highly prevalent in chickens (42,43) and tends to belong to phylogenetic group B2 (44). A future investigation will be necessary to determine whether the variety of aEPEC strains of the phylogenetic group B2 isolated from healthy individuals is from poultry origins.…”