Caracterização de Escherichia coli produtoras de toxina de Shiga (STEC) isoladas na produção de bovinos de corte e nas respectivas carcaças dos animais abatidos / Characterization of Shiga toxin-producing Escherichia coli (STEC) isolated in feedlot beef cattle production and their carcasses

Escherichia coli produtoras de toxina de Shiga (STEC) são considerados importantes patógenos de origem alimentar que apresentam o trato intestinal de ruminantes domésticos, principalmente bovinos, seu reservatório natural. Esses microrganismos estão associados com doenças severas em humanos, tais como colite hemorrágica (CH) e síndrome urêmica hemolítica (SHU). Este trabalho teve como objetivos avaliar a ocorrência de STEC em diferentes fontes, ambientais ou não, da criação e abate de bovinos confinados. Além disso, detectar a presença dos genes stx1, stx2, ehxA e eaeA; identificar cepas O157:H7 através da pesquisa do gene uidA; evidenciar a capacidade de produção de Stx e de Eh; identificar variantes de stx e de eaeA; e determinar os sorotipos a diversidade genética das cepas de STEC. A avaliação da presença dos genes (stx1, stx2, ehxA e eaeA) e da produção de Eh foi utilizada como triagem para a seleção de cepas possivelmente patogênicas, sendo que do total de 628 isolados avaliados, foram selecionadas 47 cepas STEC típicas e outras 12 consideradas como atípicas. Das STEC típicas 80,9% foram isolados provenientes de amostras de fezes, enquanto 19,1% foram de amostras de carcaças. Seis cepas isoladas de fezes e 1 de carcaça foram sorotipificadas como 0157:H7, todas positivas para a presença do gene uidA. Além do sorogrupo 0157, nenhum outro, dentre os principais causadores de surtos e casos esporádicos de CH e SHU, foi detectado...

Diferença de patogenicidade entre Escherichia coli enteroinvasora e Shigella flexneri em modelo experimental de infecção intestinal / Diference in pathogenicity between enteroinvasive Escherichia coli and Shigella flexneri in an experimental model of intestinal infection

Neste trabalho, esclarecemos tópicos da patogenicidade de EIEC que sustentam a sua menor virulência quando comparada à S. flexneri, e mostramos a importância das células dendríticas (CD) nesse processo. Estudou-se o comportamento de EIEC e S. flexneri quando em contato com células Caco-2, avaliando-se uma cinética de expressão dos genes envolvidos na invasão e disseminação bacteriana. Em geral, todos os genes foram menos expressos em EIEC, fato corroborado pelo fenótipo de disseminação bacteriana, onde EIEC foi menos eficiente do que Shigella. Também foi avaliada a modulação da resposta inflamatória de células dendríticas intestinais murinas pela produção de citocinas, expressão de moléculas co-estimulatórias e apresentação de antígenos, após desafio das células com as bactérias. Os resultados sugerem que EIEC induz a uma resposta protetora ao hospedeiro, enquanto que Shigella estaria "driblando" o sistema imune, além de provavelmente super-estimular o sistema imune adaptativo, fato que poderia levar a um agravamento da doença. As ações integradas das células Caco-2, células dendríticas e estímulos bacterianos foram estudadas em cocultura celular. Observou-se que EIEC e suas proteínas secretadas induzem a migração das CDs ao compartimento apical da co-cultura; nada foi observado quando o desafio se deu com Shigella...

Association of IL-8-inducing strains of diffusely adherent Escherichia coli with sporadic diarrheal patients with less than 5 years of age

The role of diffusely adherent Escherichia coli (DAEC) in diarrheal disease has been controversial. However, DAEC strains were recently implicated in diarrheal disease in developing countries. To clarify whether DAEC are prevalent among sporadic cases of diarrheal illness in Osaka City, Japan, E. coli strains isolated between July 1997 and March 2000 during diarrheagenic E. coli (DEC) investigation were retrospectively examined. DAEC strains were recognized among 41 (4.4 percent) of 924 patients and formed the biggest subgroup of DEC. Previously, we reported that some DAEC strains caused epithelial cells to secrete as much IL-8 as enteroaggregative E. coli strains did. In this study, we attempted to evaluate epidemiologically whether the ability of DAEC to induce IL-8 was involved in the pathogenesis. Relationship among patient age, symptoms, Afa adhesins, season and IL-8 induction were examined. The subgroup of DAEC that possessed Afa genes and/or induced a high level of IL-8 was significantly prevalent among patients age 1 to 4 years; however total DAEC was not significantly high among the children compared to other age group. IL-8 inducing DAEC seems to play a role in causing sporadic diarrheal illnesses, particularly in pediatric fields. Investigations highlighting the relationship between IL-8 induction and enteropathogenicity are clearly necessary to confirm the role of DAEC in infectious enteritis.

Papel de la Toxina Shiga en el sindrome urémico hemolítico / Role of the Shiga toxin in the hemolytic uremic syndrome

In the last years, infection associated with Shiga toxin-producing Escherichia coli (STEC) and subsequent Hemolitic-Uremic Syndrome (HUS) became relevant as a public health since it was considered as one of the most important emergent patogen present in the food contaminated by cattle feces. STEC infection may be asymptomatic or begins with a watery diarrhea that may or may not progress to bloody diarrhea (hemorrhagic colitis) and HUS. In Argentina, HUS is the most common pediatric cause of acute renal insufficiency and the second cause of chronic renal failure. Up to now, STEC infection lacks of known effective treatment strategies that diminish risk of progression to HUS. The mechanisms by which Shiga toxin (Stx) induce HUS may help to find strategies to prevent or ameliorate HUS. In this article, recent progress that has contributed to understanding the disease pathogenesis of STEC is reviewed. New strategies to prevent further uptake of Shiga from the gut, either during the diarrheal phase or once HUS has developed are discussed.

Effects of decreased cerebral perfusion pressure on cerebral hemodynamics, brain cell membrane function and energy metabolism during the early phase of experimental Escherichia coli meningitis in the newborn piglet

In this study, we tested the hypothesis that decreased cerebral perfusion pressure (CPP) induces cerebral ischemia and worsen brain damage in neonatal bacterial meningitis. Meningitis was induced by intracisternal injection of 10(9) colony forming units of Escherichia coli in 21 newborn piglets. Although CPP decreased significantly at 8 hr after bacterial inoculation, deduced hemoglobin (HbD), measured as an index of changes in cerebral blood flow by near infrared spectroscopy, did not decrease significantly. In correlation analyses, CPP showed significant positive correlation with brain ATP and inverse correlation with brain lactate levels. CPP also correlated positively with HbD and oxidized cytochrome aa3 (Cyt aa3) by near infrared spectroscopy. However, CPP did not show significant correlation with cerebral cortical cell membrane Na+,K+-ATPase activity, nor with levels of lipid peroxidation products. In summary, decreased CPP observed in this study failed to induce cerebral ischemia and further brain injury, indicating that cerebrovascular autoregulation is intact during the early phase of experimental neonatal bacterial meningitis.

Unexpected effects of pathogens on epithelial Na+ channels

No abstract available.