Toxinas de Clostridium perfringens / Toxins of Clostridium perfringens

Clostridium perfringens es un bacilo grampositivo anaerobio con capacidad de formar esporas. Es uno de los patógenos bacterianos con mayor distribución en el medio ambiente, ya que puede ser aislado de muestras de suelo y de agua y además forma parte de la microbiota intestinal de animales y humanos. Sin embargo, en ciertas ocasiones puede actuar como patógeno oportunista y causar enfermedades como la gangrena gaseosa, la enterotoxemia del ovino y del caprino y la disentería del cordero, entre otras. En humanos, está asociado a enfermedades como la intoxicación por alimentos, la enterocolitis necrotizante en niños y la enteritis necrótica o pigbel de las tribus de Papúa-Nueva Guinea. El renovado interés que existe actualmente en el estudio de C. perfringens como patógeno veterinario y humano, junto con el avance de la biología molecular, han hecho posible que la ciencia tenga hoy un conocimiento más profundo sobre la biología y la patogenia de esta bacteria. En esta revisión bibliográfica se discuten y actualizan los principales aspectos de la patogenia intestinal de C. perfringens teniendo en cuenta las toxinas con mayor importancia médica descritas hasta el presente.

Clostridium perfringens is an anaerobic gram-positive spore-forming bacillus. It is one of the pathogens with larger distribution in the environment; it can be isolated from soil and water samples, which also belongs to the intestinal flora of animals and humans. However, on some occasions it can act as an opportunistic pathogen, causing diseases such as gas gangrene, enterotoxemia in sheep and goats and lamb dysentery, among others. In human beings, it is associated to diseases such as food poisoning, necrotic enterocolitis of the infant and necrotic enteritis or pigbel in Papua-New Guinea tribes. The renewed interest existing nowadays in the study of C. perfringens as a veterinarian and human pathogen, together with the advance of molecular biology, had enabled science to have deeper knowledge of the biology and pathology of these bacteria. In this review, we discuss and update the principal aspects of C. perfringens intestinal pathology, in terms of the toxins with major medical relevance at present.

Toxins and bioactive compounds from cyanobacteria and their implications on human health.

Many species of cyanobacteria (blue-green algae) produce secondary metabolites with potent biotoxic or cytotoxic properties. These metabolites differ from the intermediates and cofactor compounds that are essential for cell structural synthesis and energy transduction. The mass growth of cyanobacteria which develop in fresh, brackish and, marine waters commonly contain potent toxins. Cyanobacterial toxins or cyanotoxins are responsible for or implicated in animal poisoning, human gastroenteritis, dermal contact irritations and primary liver cancer in humans. These toxins (microcystins, nodularins, saxitoxins, anatoxin-a, anatoxin-a(s), cylindrospermopsin) are structurally diverse and their effects range from liver damage, including liver cancer to neurotoxicity. Several incidents of human illness and more recently, the death of 60 haemodialysis patients in Caruaru, Brazil, have been linked to the presence of microcystins in water. In response to the growing concern about the non-lethal acute and chronic effects of microcystins, World Health Organization has recently set a new provisional guideline value for microcystin-LR of 1.0 microg/L in drinking water. Cyanobacteria including microcystin-producing strains produce a large number of peptide compounds, e.g. micropeptins, cyanopeptolins, microviridin, circinamide, aeruginosin, with varying bioactivities and potential pharmacological application. This article discusses briefly cyanobacterial toxins and their implications on human health.

Bacterial endotoxin induces changes in the organization and expression of actin and modulation of the cell membrane of microglia

Background and In situ there are at least three morphologically and functionally different forms of microglia: the resting, the activated, and the phagocytic microglia. The signals promoting the morphological changes which adapt microglia to specific functions are still unknown. In this study the effect of bacterial wall lipopolysaccharide [LPS] on the morphology and organization and expression of actin in microglia was investigated. In addition, the changes in the appearance of the cell membrane were investigated. Microglia cultures were prepared from neopallia of newborn mice and treated with LPS. Scanning electron microscopy, labeling with phalloidin, and immunoblotting were used. The majority of nontreated microglia were ameboid in shape with many short processes that extended into lamellipodia. When microglia were treated with LPS most of the microglia acquired a large, round, and flat shape. The rest of the ameboid microglia became larger in size. Fluorescent labeling with phalloidin showed that the F-actin network appeared diffusely arranged throughout the cytoplasm of nontreated microglia. In LPS-treated microglia the F-actin network was reorganized into filamentous bundles extending into microspike-like projections. Using scanning electron microscopy, the nontreated microglia had large membrane folds and few large blebs. In LPS-treated microglia most of the membrane folds and blebs at the cell periphery disappeared with the appearance of many microspike-like projections. Immunoblotting showed that LPS-treated microglia upregulated their actin protein. Conclusions: These changes in the organization of F-actin and the cell membrane may reflect adaptation of activated microglia to specific functional activity, such as increases in their phagocytic activity

Control de alimentos y las aflatoxinas / Food control and aflatoxics

Entre los microorganismos que producen la contaminacion de los alimentos de consumo humano, se encuentra el Aspergillus flavus, a traves del factor toxico denominado Aflatoxina. las condiciones de temperatura de 20 a 38 grados centigrados los niveles de humedad de 14 a 30 por ciento , la presencia de nutrientes, ogigeno, etc, favorecen el desarrollo de estos hongos y la produccion de toxinas en los alimentos, producto de las inadecuadas condiciones higienico sanitarias. A todo esto se suman las dificultades economicas de los paises en desarrollo, donde existen problemas de desnutricion, patologias gastro-intestinales, enfermedades carenciales y un mayor consumo de hidratos de carbono, que proteinas, lo que incrementa la sensibilidad de la poblacion a las sustancias toxicas. El cancer hepatico es uno de los principales efectos patologicos relacionados con la aflatoxina, cuyo nivel de tolerancia en los productos alimenticios esta entre 3 a 25 mcg/Kg (5mcg/Kg para aflatoxina B1, que es la mas toxica). En Bolivia, INLASA acepta 10 mcg/Kg como nivel de tolerancia. La deteccion de aflatoxinas en el arroz vietnamita introducido al pais, debe ser el punto de partida para implementar un sistema de prevencion y control de alimentos contaminados, con la participacion de la poblacion y una coordinacion interinstitucional decidida