Academic literature on the topic 'Enterotoxina T (BceT)'

ABSTRACT Many strains of Bacillus cereus cause gastrointestinal diseases, and the closely related insect pathogen B. thuringiensis has also been involved in outbreaks of diarrhea. The diarrheal types of diseases are attributed to enterotoxins. Two different enterotoxic protein complexes, hemolysin BL (HBL) and nonhemolytic enterotoxin (NHE), and an enterotoxic protein, enterotoxin T, have been characterized, and the genes have been sequenced. PCR primers for the detection of these genes were deduced and used to detect the genes in 22 B. cereus and 41 B. thuringiensis strains. At least one gene of each of the two protein complexes HBL and NHE was detected in all of the B. thuringiensis strains, while six B. cereus strains were devoid of all three HBL genes, three lacked at least two of the three NHE genes, and one lacked all three. Five different sets of primers were used for detection of the gene (bceT) encoding enterotoxin T. The results obtained with these primer sets indicate that bceT is widely distributed among B. cereusand B. thuringiensis strains and that the gene varies in sequence among different strains. PCR with the two primer sets BCET1-BCET3 and BCET1-BCET4 unambiguously detected the bceTgene, as confirmed by Southern analysis. The occurrence of the genes within the two complexes is significantly associated, while neither the occurrence of the two complexes nor the occurrence of thebceT gene is significantly associated in the 63 strains. We suggest an approach for detection of enterotoxin-encoding genes inB. cereus and B. thuringiensis based on PCR analysis with the six primer sets for the detection of genes in the HBL and NHE operons and with the BCET1, BCET3, and BCET4 primers for the detection of bceT. PCR analysis of the 16S-23S rRNA gene internal transcribed spacer region revealed identical patterns for all strains studied.

ABSTRACT With the exceptions of Bacillus cereus and Bacillus anthracis, Bacillus species are generally perceived to be inconsequential. However, the relevance of other Bacillus species as food poisoning organisms and etiological agents in nongastrointestinal infections is being increasingly recognized. Eleven Bacillus species isolated from veterinary samples associated with severe nongastrointestinal infections were assessed for the presence and expression of diarrheagenic enterotoxins and other potential virulence factors. PCR studies revealed the presence of DNA sequences encoding hemolysin BL (HBL) enterotoxin complex and B. cereus enterotoxin T (BceT) in five B. cereus strains and in Bacillus coagulans NB11. Enterotoxin HBL was also harbored by Bacillus polymyxa NB6. After 18 h of growth in brain heart infusion broth, all seven Bacillus isolates carrying genes encoding enterotoxin HBL produced this toxin. Cell-free supernatant fluids from all 11 Bacillus isolates demonstrated cytotoxicity toward human HEp-2 cells; only one Bacillus licheniformis strain adhered to this test cell line, and none of the Bacillus isolates were invasive. This study constitutes the first demonstration that Bacillus spp. associated with serious nongastrointestinal infections in animals may harbor and express diarrheagenic enterotoxins traditionally linked to toxigenic B. cereus.

Dissertação de Mestrado Integrado em Medicina Veterinária
Os microrganismos do grupo Bacillus cereus são causadores de patologia gastrointestinal, podendo ocorrer duas formas da doença: a síndrome diarreica e a síndrome emética. A forma diarreica é causada pela presença de enterotoxinas. São várias as enterotoxinas produzidas por B. cereus. Existem duas toxinas tripartidas, a hemolisina BL (HBL) e a enterotoxina não hemolítica (NHE), a citotoxina K (CytK), a enterotoxina T e a enterotoxina FM. Este estudo consistiu na pesquisa de genes que codificam enterotoxinas, por PCR (reacção de polimerase em cadeia) em tempo real, em 76 isolados alimentares, provenientes da colecção de bactérias do Laboratório de Bromatologia e Defesa Biológica do Exército. As bactérias utilizadas neste estudo foram caracterizadas morfologicamente, através do isolamento em MYP e agar sangue, e bioquimicamente utilizando a galeria API 50 CH®. Das 76 estirpes analisadas 28 revelaram-se positivas para a toxina HBL, 27 para a NHE, 43 para a enterotoxina T e nenhuma estirpe foi positiva para a citotoxina K. Em suma, 58 das 76 estirpes de B. cereus sensu lato utilizadas neste trabalho são potencialmente patogénicas. Os resultados obtidos demonstraram a existência de uma grande variabilidade de estirpes B. cereus potencialmente produtoras de enterotoxinas isoladas de alimentos.
ABSTRACT - Many strains of Bacillus cereus group cause gastrointestinal diseases, which include two types: diarrheal and emetic syndromes. The diarrheal type of disease is attributed to enterotoxins. Many enterotoxins are produced by B. cereus. The enterotoxins include two tri-partied toxins, hemolysin BL (HBL) and nonhemolytic enterotoxin (NHE), cytotoxin K, enterotoxin T and finally enterotoxin FM. The primary objective of this study was the detection of gene enterotoxins, by real-time PCR (polimerase chain reaction), produced by 76 strains isolated from food samples. Those strains were included in a bacterial collection from LBDBE. The strains used in this study were characterized based on morphological data, like the presence or absence of haemolysis, and biochemical information, using the test API 50 CH®. 28 strains were positive for toxin HBL, 27 for NHE and 43 were positive to enterotoxin T. None of the strains were positive to cytotoxin K. The results showed a high variability in potencial enterotoxic B. cereus strains isolated from food.

Bacillus cereus is primarily a soil-dwelling bacterium, however it is also pathogenic bacterium, which is implicated in many food poisoning outbreaks throughout the world. It is responsible for both non-gastrointestinal and gastrointestinal infection with the former leading to many working days lost. Two types of infection exist, the emetic Infection and the diarrhoeal infection. The emetic infection is caused by a heat stable protein, which causes vomiting and stomach cramps. The diarrhoeal infection is caused by several different toxins including haemolysin BL (HBL), non-haemolytic enterotoxin (NHE), B. cereus enterotoxin T (bceT), cytotoxin K (cytK), the recently discovered Hlyll toxin and enterotoxin Fm (entFM). The purpose of this project was to develop a reporter system that could be used to investigate the environmental conditions necessary for the production of Bacillus cereus enterotoxin T (bceT) after human ingestion. A plasmid was constructed that carried the bceT gene, which would ultimately be integrated Into the B. cereus chromosome after manipulation.