Detection and sequences of the enteroaggregative Escherichia coli heat-stable enterotoxin 1 gene in enterotoxigenic E. coli strains isolated from piglets and calves with diarrhea

Abstract

Enterotoxigenic Escherichia coli (ETEC) strains isolated from piglets and calves with diarrhea were tested for the presence of the enteroaggregative E. coli enterotoxin 1 (EAST1) gene sequences by PCR and colony hybridization. The EAST1 gene was found in most porcine ETEC strains with adherence factor K88, especially in those elaborating heat-labile enterotoxin. One porcine ETEC strain with adherence factor K99 was also positive for the EAST1 gene. In contrast, 987P-positive (987P ؉) ETEC strains from piglets, K99 ؉ ETEC strains from calves, and K99 ؉ F41 ؉ or F41 ؉ ETEC strains from piglets and calves were negative for the EAST1 gene. The K88ab ؉ or K88ac ؉ ETEC strains tested possessed the EAST1 gene on a plasmid that was distinct from a K88-encoding plasmid. The EAST1 gene sequences of the K88 ؉ ETEC strains were identical to each other and 99.1 and 98.3% homologous to the previously reported sequences of ETEC strains colonizing humans and enteroaggregative E. coli strains, respectively. The data indicate that the EAST1 gene is distributed among porcine ETEC strains in association with the adherence factor type. Escherichia coli is a normal inhabitant of the intestinal tracts of animals. However, particular E. coli strains such as enterotoxigenic E. coli (ETEC) (10, 18, 32) and Vero cytotoxinproducing E. coli (30) are associated with diarrhea; ETEC has been proved to be a dominant bacterial agent of diarrheal diseases in piglets and calves (1, 14). Adherence to mucosa is the initial, essential step in the development of pathogenicity for diarrhea-associated E. coli (16). Most ETEC strains from piglets with diarrhea possess the pilus adherence factor K88 (including K88ab, K88ac, and K88ad), 987P, K99, or F41 (10, 32); of those, K88 is the predominant adherence factor (27, 34, 36). In contrast, ETEC strains from calves with diarrhea, in most cases, possess K99 alone or a combination of K99 and F41 (10, 32). ETEC strains elaborate heat-labile enterotoxin (LT) that is similar to cholera toxin and/or heat-stable enterotoxin I (STI) or II (STII) (3, 11). K88-positive (K88 ϩ) ETEC strains are usually LT ϩ , LT ϩ , STI ϩ , or LT ϩ STII ϩ , and K99 ϩ or 987P ϩ ETEC strains are STI ϩ in most cases (12, 22, 34). Some strains of enteroaggregative E. coli (EAggEC), the most recently recognized category of human diarrheagenic E. coli, elaborate an enterotoxin of 38 amino acids named EAggEC heat-stable enterotoxin 1 (EAST1) (28, 29). EAST1 of EAggEC and STI of ETEC are genetically and immunologically distinct enterotoxins (29). EAST1 is detected in the rabbit intestinal model (28), and STI is detected in suckling mice (4). EAST1 activates guanylate cyclase, as does STI (28). The EAST1 gene was also found in ETEC strains pathogenic for humans (37) or in a subgroup of diffusely adhering E. coli (DAEC) strains isolated from patients with diarrhea (39). In this study, we investigated the presence of the EAST1 gene in ETEC strains isolated from piglets and calves with diarrhea and determined the EAST1 gene sequences distributed a...

Genetic relatedness of commensal Escherichia coli from nursery pigs in intensive pig production in Denmark and molecular characterization of genetically different strains

“…The gene (astA) encoding the production of EAST1, a plasmidencoded enterotoxin, has been detected in several groups of diarrhoeagenic E. coli (EAEC (Enteroaggregative Escherichia coli), EPEC, ETEC and STEC (Shiga toxinproducing Escherichia coli)) isolated from humans and pigs. The pathogenic significance of EAST1 in diarrhoea in pigs is not known (Yamamoto and Nakazawa 1997;Choi et al 2001;Frydendahl 2002;Noamani et al 2003;Osek 2003). Of note is also that the gene iss (involved in serum resistance), usually associated with poultry disease and suggested to be a gene used to separate chicken isolates from the majority of isolates from mammalian sources (David et al 2010) was found in 14 different profiles.…”

Weapons of mass destruction: virulence factors of the global killer EnterotoxigenicEscherichia coli

“…In contrast to STa and STb, the 38 amino acid EAST1 toxin is less well characterized both in terms of function and contribution to ETEC-mediated disease. While EAST1 was originally isolated from EAEC strain 17-2, it has now been identified in other pathotypes of E. coli including ETEC strains from human and animal sources (Yamamoto & Echeverria, 1996;Yamamoto & Nakazawa, 1997;Veilleux & Dubreuil, 2006). However, the role of EAST1 in mediating diarrhoea remains controversial; while several epidemiological studies have implicated the toxin in mediating disease (Menard & Dubreuil, 2002;Veilleux & Dubreuil, 2006), EAEC strain 17-2 failed to elicit diarrhoea in human volunteer studies (Nataro et al, 1995).…”

Role of Escherichia coli in acute diarrhoea in tribal preschool children of central India

“…Multiplex PCR using published primers (Appendix 1 [8][9][10][11][12][13][14][15] ) was performed in a total reaction volume of 50 mL (Master mix -12.5 mL, reverse and forward oligonucliotide primers -50 pmol, and boiled suspension as template DNA -6.0 mL). The amplification was performed in thermal mini cycler (M. J.…”