title: Avian extraintestinal Escherichia coli exhibits enterotoxigenic-like activity in the in vivo rabbit ligated ileal loop assay.
abstract: Avian pathogenic Escherichia coli (APEC) strains harbor a number of virulence genes and cause extraintestinal diseases, such as septicemia, swollen-head syndrome, salpingitis, and omphalitis in poultry. APEC strains are not known to cause intestinal diseases. Herein, for the first time, it is reported that APEC strains were able to induce an enterotoxigenic-like effect in rabbit ligated ileal loops. Strain SEPT362 caused cell detachment of the intestinal villi, which also showed a flattened and wilted appearance, but the integrity of the tight junctions was maintained. Additionally, this strain did not adhere to enterocytes in vivo, although adhesin encoding genes ( fimH, csgA, lpfA2-3, and ECP) were present while other lpfA types, sfa, afa, papC, and ral genes were not. This enterotoxigenic-like activity was conserved after thermal treatment of the supernatant at 65°C but not at 100°C. Moreover, experiments based on filtering with different molecular weight cut-off (MWCO) pore sizes demonstrated that the component associated with the observed biological effect has a molecular weight >100 kDa. Blast search and polymerase chain reaction assays for known E. coli virulence factors showed that strain SEPT362 harbors the gene encoding for the toxin EAST-1 and the serine protease autotransporter (SPATE) Tsh, but is negative for genes encoding for the toxins LT-I, STh, STp, Stx1, Stx2, CNF-1, CNF-2, CDT and the SPATEs Sat, Pic, Vat, SigA, SepA, EatA, EspP, or EspC. A cloned copy of the tsh gene in E. coli K-12 was also tested and was shown to have an enterotoxic effect. These results suggest that APEC might induce fluid accumulation in the rabbit gut. The Tsh autotransporter seems to be one of the factors associated with this phenotype.
authors.affiliation: 1 Bacterial Molecular Biology Laboratory, Department of Genetics, Evolution, and Bioagents, Biology Institute, State University of Campinas (UNICAMP) , Campinas, São Paulo, Brazil .
authors.forename: Renato Pariz
authors.initials: RP
authors.lastname: Maluta
authors.forename: Maria Silvia Viccari
authors.initials: MS
authors.lastname: Gatti
authors.forename: Paulo Pinto
authors.initials: PP
authors.lastname: Joazeiro
authors.forename: Jacqueline Boldrin
authors.initials: JB
authors.lastname: de Paiva
authors.forename: Thaís Cabrera Galvão
authors.initials: TC
authors.lastname: Rojas
authors.forename: Flávio
authors.initials: F
authors.lastname: Silveira
authors.forename: Sébastien
authors.initials: S
authors.lastname: Houle
authors.forename: Renata Katsuko Takayama
authors.initials: RK
authors.lastname: Kobayashi
authors.forename: Charles M
authors.initials: CM
authors.lastname: Dozois
authors.forename: Wanderley
authors.initials: W
authors.lastname: Dias da Silveira
mesh_terms: D018830:Adhesins, Escherichia coli / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity; D000818:Animals; D001422:Bacterial Adhesion; D002645:Chickens / Q000382:microbiology; D004751:Enteritis / Q000382:microbiology* / Q000473:pathology / Q000503:physiopathology; D054307:Enterotoxigenic Escherichia coli / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D004768:Enterotoxins / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity; D004927:Escherichia coli Infections / Q000382:microbiology* / Q000473:pathology / Q000503:physiopathology / Q000662:veterinary; D006358:Hot Temperature; D007082:Ileum / Q000378:metabolism / Q000382:microbiology* / Q000648:ultrastructure; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism / Q000382:microbiology* / Q000648:ultrastructure; D008099:Liver / Q000382:microbiology; D008297:Male; D011201:Poultry Diseases / Q000382:microbiology; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism / Q000633:toxicity; D018805:Sepsis / Q000382:microbiology / Q000662:veterinary; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D014883:Water-Electrolyte Imbalance / Q000209:etiology
chemical_list: D018830:Adhesins, Escherichia coli; D004768:Enterotoxins; D011994:Recombinant Proteins; D037521:Virulence Factors; C112027:tsh protein, E coli