title: Production and release of heat-labile toxin by wild-type human-derived enterotoxigenic Escherichia coli.
abstract: Production and release of heat-labile toxin (LT) by wild-type enterotoxigenic Escherichia coli (ETEC) strains, isolated from diarrheic and asymptomatic Brazilian children, was studied under in vitro and in vivo conditions. Based on a set of 26 genetically diverse LT(+) enterotoxigenic E. coli strains, cell-bound LT concentrations varied from 49.8 to 2415 ng mL(-1). The amounts of toxin released in culture supernatants ranged from 0% to 50% of the total synthesized toxin. The amount of LT associated with secreted membrane vesicles represented <5% of the total toxin detected in culture supernatants. ETEC strains secreting higher amounts of LT, but not those producing high intracellular levels of cell-bound toxin, elicited enhanced fluid accumulation in tied rabbit ileal loops, suggesting that the strain-specific differences in production and secretion of LT correlates with symptoms induced in vivo. However, no clear correlation was established between the ability to produce and secrete LT and the clinical symptoms of the infected individuals. The present results indicate that production and release of LT by wild-type human-derived ETEC strains are heterogeneous traits under both in vitro and in vivo growth conditions and may impact the clinical outcomes of infected individuals.
authors.affiliation: Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Melissa Ang Simões
authors.initials: MA
authors.lastname: Lasaro
authors.forename: Juliana Falcão
authors.initials: JF
authors.lastname: Rodrigues
authors.forename: Camila
authors.initials: C
authors.lastname: Mathias-Santos
authors.forename: Beatriz Ernestina Cabílio
authors.initials: BE
authors.lastname: Guth
authors.forename: Adriana
authors.initials: A
authors.lastname: Régua-Mangia
authors.forename: Antônio José
authors.initials: AJ
authors.lastname: Piantino Ferreira
authors.forename: Mickie
authors.initials: M
authors.lastname: Takagi
authors.forename: Joaquin
authors.initials: J
authors.lastname: Cabrera-Crespo
authors.forename: Maria Elisabete
authors.initials: ME
authors.lastname: Sbrogio-Almeida
authors.forename: Luís Carlos
authors.initials: LC
authors.lastname: de Souza Ferreira
mesh_terms: D000818:Animals; D004768:Enterotoxins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D004927:Escherichia coli Infections / Q000382:microbiology; D006358:Hot Temperature; D006801:Humans; D011817:Rabbits
chemical_list: D004768:Enterotoxins