ST-Producing E. coli Oppose Carcinogen-Induced Colorectal Tumorigenesis in Mice.

There is a geographic inequality in the incidence of colorectal cancer, lowest in developing countries, and greatest in developed countries. This disparity suggests an environmental contribution to cancer resistance in endemic populations. Enterotoxigenic bacteria associated with diarrheal disease are prevalent in developing countries, including enterotoxigenic E. coli (ETEC) producing heat-stable enterotoxins (STs). STs are peptides that are structurally homologous to paracrine hormones that regulate the intestinal guanylyl cyclase C (GUCY2C) receptor. Beyond secretion, GUCY2C is a tumor suppressor universally silenced by loss of expression of its paracrine hormone during carcinogenesis. Thus, the geographic imbalance in colorectal cancer, in part, may reflect chronic exposure to ST-producing organisms that restore GUCY2C signaling silenced by hormone loss during transformation. Here, mice colonized for 18 weeks with control E. coli or those engineered to secrete ST exhibited normal growth, with comparable weight gain and normal stool water content, without evidence of secretory diarrhea. Enterotoxin-producing, but not control, E. coli, generated ST that activated colonic GUCY2C signaling, cyclic guanosine monophosphate (cGMP) production, and cGMP-dependent protein phosphorylation in colonized mice. Moreover, mice colonized with ST-producing E. coli exhibited a 50% reduction in carcinogen-induced colorectal tumor burden. Thus, chronic colonization with ETEC producing ST could contribute to endemic cancer resistance in developing countries, reinforcing a novel paradigm of colorectal cancer chemoprevention with oral GUCY2C-targeted agents

Mode of disulfide bond formation of a heat-stable enterotoxin (STh) produced by a human strain of enterotoxigenic Escherichia coli

AbstractTo determine the modes of three disulfide linkages in the heat-stable enterotoxin (STh) produced by a human strain of enterotoxigenic Escherichia coli, we synthesized STh(6–18), which consists of 13 amino acid residues and has the same intramolecular disulfide linkages as native STh [(1985) FEBS Lett. 181, 138–142], by stepwise and selective formation of disulfide bonds using different types of removable protecting groups for the Cys residues. Synthesis of the peptide with different modes of disulfide bond formation provided three peptides consistent with standard STh(6–18) in their physicochemical and biological properties, thereby indicating that the disulfide bonds in STh(6–18) are

Different Assay Conditions for Detecting the Production and Release of Heat-Labile and Heat-Stable Toxins in Enterotoxigenic Escherichia coli Isolates

Enterotoxigenic Escherichia coli (ETEC) produce heat-labile (LT) and/or heat-stable enterotoxins (ST). Despite that, the mechanism of action of both toxins are well known, there is great controversy in the literature concerning the in vitro production and release of LT and, for ST, no major concerns have been discussed. Furthermore, the majority of published papers describe the use of only one or a few ETEC isolates to define the production and release of these toxins, which hinders the detection of ETEC by phenotypic approaches. Thus, the present study was undertaken to obtain a better understanding of ST and LT toxin production and release under laboratory conditions. Accordingly, a collection of 90 LT-, ST-, and ST/LT-producing ETEC isolates was used to determine a protocol for toxin production and release aimed at ETEC detection. for this, we used previously raised anti-LT antibodies and the anti-ST monoclonal and polyclonal antibodies described herein. the presence of bile salts and the use of certain antibiotics improved ETEC toxin production/release. Triton X-100, as chemical treatment, proved to be an alternative method for toxin release. Consequently, a common protocol that can increase the production and release of LT and ST toxins could facilitate and enhance the sensitivity of diagnostic tests for ETEC using the raised and described antibodies in the present work.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Butantan Inst, Bacteriol Lab, BR-05503900 São Paulo, BrazilSão Paulo Trop Med Inst, Seroepidemiol & Immunol Lab, BR-05403000 São Paulo, BrazilFleury Med & Hlth, BR-04344903 São Paulo, BrazilButantan Inst, Immunopathol Lab, BR-05503900 São Paulo, BrazilButantan Inst, Immunochem Lab, BR-05503900 São Paulo, BrazilAdolfo Lutz Inst, Bacteriol Sect, BR-01246000 São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol, BR-04923062 São Paulo, SP, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol, BR-04923062 São Paulo, SP, BrazilWeb of Scienc

Heat-Labile Enterotoxin: Beyond GM1 Binding

Enterotoxigenic Escherichia coli (ETEC) is a significant source of morbidity and mortality worldwide. One major virulence factor released by ETEC is the heat-labile enterotoxin LT, which is structurally and functionally similar to cholera toxin. LT consists of five B subunits carrying a single catalytically active A subunit. LTB binds the monosialoganglioside GM1, the toxin’s host receptor, but interactions with A-type blood sugars and E. coli lipopolysaccharide have also been identified within the past decade. Here, we review the regulation, assembly, and binding properties of the LT B-subunit pentamer and discuss the possible roles of its numerous molecular interactions

Caracterização sorológica dos antígenos somáticos e perfil de resistência antimicrobiana de cepas de Escherichia coli isoladas de suínos com diarréia no Estado do Paraná

Orientador: Waldir HamannDissertaçao (mestrado) - Universidade Federal do Paraná, Setor de Ciencias AgráriasResumo: O presente trabalho teve como objetivos a caracterização sorológica e o perfil de resistência aos antimicrobianos de 42 cepas de Escherichia coli isoladas em surtos de diarréia suína no Estado do Paraná, no Centro de Diagnóstico Marcos Enrietti, em Curitiba, PR. Os antígenos somáticos O, K e F foram identificados através da técnica de soroaglutinação em lâmina no Centro de Pesquisas Veterinárias Desidério Fínamor, em Guaíba, RS. A resistência aos antimicrobianos foi verificada através do método de difusão em disco. Os sorogrupos 0138 : K81 e 0141 : K85 ocorreram na mesma proporção em 21,4% das amostras: 0139 : K82 em 9,5% e 0149 : K91 em 7,1%. Os sorogrupos 035 : ICV79", 0108 : KV189", 0115 : K"V165" e 0119 : K'V113" foram encontrados em 2,4% das amostras. Entre as 35 cepas investigadas quanto aos antígenos de aderência, na Universidade de Campinas, a fímbria F4 foi detectada em 62,8% das amostras. 0 antígeno F165 ocorreu em 14,3% das cepas sendo este o primeiro relato da ocorrência deste antígeno em suínos no Brasil. Observou-se resistência múltipla em 68,7% das cepas isoladas.Abstract: The objectives of the present work were the serological characterization and the determination of the antibiotic resistance profile of 42 strains of Escherichia coli isolated during outbreaks of swine diarrhea in the State of Parana at the Center of Veterinary Diagnostic Marcos Enrietti, in Curitiba, PR. The somatic antigens O, K and F were identified through the method of seroglutination at Center of Veterinary Researches Desidério Finamor, in Guaíba, RS. The resistance to anti-microbial drugs was verified through the diffusion method. Serogroups 0138 : K81 and 0141 : K85 occurred in the same proportion in 21,4% of the samples; 0139 : K82 in 9,5% and 0149 : K91 in 7,1%. The serogroups 035 : KV79", 0108 : K"V189", 0115 : K"V165" and 0119 : KV113" were found in 2,4% of the strains. In 35 strains were verified the fimbrial antigens at Campinas University. The antigen F4 was detected in 62,8% of strains and the F165 in 14,3%. This is the first report of the occurrence of the fimbrial antigen named F165 in Brazil. Multiple resistance was observed in 68,7% of the strains isolated

Mécanismes moléculaires de régulation de l'activité du récepteur A des peptides natriurétiques

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal