Detección de citotoxinas de escherichia coli enterohemorrágica en productos cárnicos chilenos e importados / Detection of shiga-like toxin producing escherichia coli in chilean and imported meat products

Escherichia coli enterohemorrágica (ECEH) está catalogada como un patógeno emergente asociado al consumo de carnes contaminadas. Con el fin de establecer la importancia de los alimentos cárnicos chilenos e importados de venta libre en Santiago de Chile en la transmisión de infecciones por ECEH, se determinó la presencia de citotoxina stx1 y stx2 en dichos alimentos. Se analizaron 213 muestras cárnicas (157 chilenas y 56 importadas) por una prueba de inmunoensayo enzimático Premier, EHEC (Meridian Diagnostics Inc, Cincinnati, U.S.A.). Del total analizado, 9 (4,2 por ciento) muestras que correspondieron a 5 de carne de vacuno chilena, 2 de hamburguesas chilenas y 2 de carne de vacuno paraguaya, presentaron valores positivos a la presencia de citotoxina(s). De acuerdo a estos resultados, es necesario mantener el control microbiológico de ECEH en estos alimentos, con el fin de prevenir la aparición de brotes de intoxicación alimentaria en el país

Escherichia coli enterohemorrágica en el síndrome hemolítico urémico, en niños chilenos: evaluación de diferentes técnicas de diagnóstico de infección / Enterohemorrhagic escherichia coli in hemolytic uremic syndrome, in chilean children: evaluation of different technics of infection diagnosis

Enterohemorrhagic escherichia coli (EHEC), have been associated with pathogenesis of hemolytic uremic syndrome (HUS) worldwide. Our aim was to determine the association of EHEC ing¿fection and HUS in chilean children. During may 1991 and october 1993, 34 children HUS and 33 age matched controls (children with diarrhea that did not develop HUS) were enrolled in a case/control study. For each child a stool and serum sample were obtained at admission. Stools were processed for common enteropathogen and for EHEC identification. EHEC were identified in stools by gene probes for different virulence factors (EHEC plasmid-associated fimbria, Shiga-like toxin I, Shiga-like toxin II and eae adherence factor) and by detection of free fecal toxin by neutralization assay in Vero cells. Sera were processed for anti-cytotoxin antibodies also by an assay in Vero cells. Enteropathogens were isolated in 20.6 percent and 15.5 percent of HUS and control children respectively (p=NS). 91 percent of the HUS children and 73 percent of the control children were EHEC positive by one or more of the techniques used (p=0.05). Of the 3 detection methods used for EHEC, only free fecal cytotoxin was significantly more common in HUS children than controls (45.5 percent vs 9 percent p=0.007). Genotype patterns of HUS and controls strains were similar except for a trend towards a higher frequency of non-toxigenic strains in the control group. Serogroup 0157 was more common in HUS children than in controls (9 percent vs 0 percent p=0.036). In Chile as in other countries, EHEC infection is common and significantly associated with occurrence of HUS. Infection with EHEC strains 0157 seems to be important risk factor for HUS

Production of cytotoxins and enterotoxins by strains of Shigella and Salmonella isolated from children with bloody diarrhea

The role of toxins in the pathogenesis of bloody diarrhea caused by Shigella and Salmonella isolated from children with bloody diarhea was studied for production of toxins active on cells in culture and in rat intestinal loops. Humman epithelial cellls from colon carcinoma (HT-29), Chinese hamster ovary cells (CHO) and kidney fibroblast from rhesus monkey (Vero) were used to detect cytotoxins. On HT-29 almost 50 percent of the Shigella and about 20 percent of the Salmonella strain caused rounding of cells; on CHO over 50 percent Salmonella and 20 percent of Shigella strains caused elongation of cells, some strains caused also rounding of these cells whereas on Vero over 60 percent of Salmonella and 40 percent of Shigella strains caused rounding of cells. Cytotoxicity on Vero and CHO cells was strongly inhibited with cholera toxin antiserum, whereas that on HT-29 was inhibited with C. difficile toxin B antiserum. Cytotonic activity on CHO cells and rounding on Vero cells seem to be suitable models to detect toxins cross-reacting with cholera toxin. Both species, Shigella and Salmonella, produce cytotoxins and enterotoxins which could play a role in intestinal disease

Production of enterotoxin and cytotoxin by aeromonas veronii

Fourteen strains of Aeromonas veronii were isolated from salt and fresh water in Rio de Janeiro and investigated for the presence of birulence factors. Eleven (79%) A. veronii strains were positive for enterotoxin by the suckling-mouse test and thirteen (93%) produced hemolysin. Of the 13 A. veronii strains that produced hemolysin, seven were investigated for cytotoxin production using Vero cells as indicator cells and all of them were positive

A cytotoxic substance produced by a wild culture of Lactobacillus casei D-34 against tumour cells.

A wild lactic culture isolated from dahi (fermented milk) sample and characterised as L. casei D-34 was found to be significantly cytotoxic (34-36%) against three tumour cell lines, HeLa, HEp-2 and HFS-9. The cytotoxic substance (CS) was found to be in the culture supernatants, protein in nature, with a molecular weight ranging from 17,000-20,000. The crude culture supernatant was partially purified by dialysis and ion exchange chromatography as anionic, cationic and neutral fractions. Among the fractions, except for the anionic fraction, others were found to be highly cytotoxic against all three tumour cell lines. The cationic, neutral and pooled (anionic:cationic:neutral in 1:1:1 ratio) fractions showed 50, 70, 70% cytotoxicity against Hep-2 cells, 70, 88, 94% against HFS-9 cells and 50, 89, 90% against HeLa cells respectively. Pooled fraction was found to exhibit higher percent of cytotoxicity compared to individual fractions indicating a synergistic effect. (3H)-thymidine incorporation studies revealed that CS and its fractions inhibited DNA synthesis in tumour cells. The CS was stable towards heat and pH changes.

Do snake venom cytoloxins eschibit amphiphilicity?

It is suggested, on the basis of the structural information available from the literature, that the molecules of cobramine B and homologous cytotoxins, in contrast to snake venom neurotoxins, are amphiphilic in the sense that they are composed of a predominantly hydrophobic multi-stranded ß-sheet and other regions sharply hydrophilic. It is possible that the direct lytic activity of snake venom cytotoxins is due, at least in part, to their amphiphathy