Avian extraintestinal Escherichia coli exhibits enterotoxigenic-like activity in the in vivo rabbit ligated ileal loop assay.

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.

Estudo citogenético in vivo e in vitro do efeito do fator citotóxico necrosante (CNF) de E. coli / Cytogenetic study in vivo and in vitro the effect of cytotoxic necrotizing factor (CNF) E. coli

Para testar o efeito clastogênico, aneugênico e tóxico do CNF (cytotoxic necrotizing factor) de E. coli foram realizados estudos citogenéticos em dois sistemas: in vivo, utilizando-se células de medula óssea de camundongos e in vitro, em cultura temporária de linfócitos humanos. Quarenta e oito animais foram utilizados para o estudo in vivo. Quatro grupos de doze animais foram submetidos a quatro tratamentos diferentes: o grupo CSM (controle com manipulaçao) nao recebeu extrato sonicado de E. coli, linhagem C-600, que nao produz o fator tóxico CNF, considerado controle negativo. O grupo T+ recebeu extrato sonicado contendo a toxina positiva de E. coli ISS-51, na menor diluiçao, enquanto o grupo T++ recebeu a mesma toxina na maior diluiçao. No sistema in vitro cinco doadores foram utilizados. Três amostras de cada indivíduo foram submetidas aos três tratamentos: CSM, CCM e T+. Preparaçoes citológicas para os estudos citogenéticos foram montadas para análise microscópica de: falhas ou "gaps", aberraçoes cromossômicas, índice mitótico e eritróticos micronucleares...