Inhibitory Effect of Flower-Shaped Zinc Oxide Nanostructures on the Growth and Aflatoxin Production of a Highly Toxigenic Strain of Aspergillus flavus Link.

Flower-shaped zinc oxide (ZnO) nanostructures were prepared via a simple aqueous precipitation strategy at room temperature. The as-grown nanostructures were characterized by UV⁻vis spectroscopy, UV⁻vis diffuse reflectance spectroscopy (DRS), spectrofluorometry, Fourier transform infrared (FTIR) spectroscopy with attenuated total reflection (ATR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). The antifungal and anti-aflatoxigenic activities of the ZnO nanostructures were further investigated using a highly toxigenic strain of Aspergillus flavus Link under in vitro and in situ conditions. The results showed that the A. flavus isolate was inhibited to various extents by different concentrations of ZnO nanostructures, but the best inhibitions occurred at 1.25, 2.5, and 5 mM in the culture media. At these concentrations, suppression of aflatoxin biosynthesis (99.7%) was also observed. Moreover, a reasonable reduction in the aflatoxin content (69%) was observed in maize grains treated with the lowest ZnO concentration that exhibited the strongest inhibitory activity in the liquid media. SEM micrographs clearly indicate multiple degenerative alterations in fungal morphology after treatment with ZnO such as damage of the tubular filaments, loss of hyphae shape, as well as hyphae rupture. These results suggest that flower-shaped ZnO nanostructures exhibit strong antifungal and anti-aflatoxigenic activity with potential applications in the agro-food system.

Identification of an immunogenic protein of Actinobacillus seminis that is present in microvesicles.

Actinobacillus seminis is a gram-negative bacterium of the Pasteurellaceae family that is involved in ovine epididymitis. Looking for a protein specific to this species, we determined the protein profile of subcellular fractions of A. seminis (American Type Culture Collection number 15768): proteins from the outer membrane (OMPs), inner membrane (IMPs), and cytoplasm (CPs). These profiles provide the first data, to our knowledge, regarding subcellular fractions of A. seminis. In the OMP fraction, we identified a protein with a molecular mass of 75 kDa that proved to be immunogenic and apparently specific for A. seminis. This conclusion was based on the reaction of hyperimmune serum of rabbits inoculated with whole cells of A. seminis that was tested against sonicated complete cells of reference strains and field isolates of Brucella ovis, Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni. No protein of these bacteria cross-reacted with the 75-kDa protein of A. seminis. Furthermore, when each type of hyperimmune serum was tested against the sonicated cells and each of the subcellular fractions of A. seminis, it did not recognize the A. seminis 75-kDa protein. We also isolated and identified this protein in microvesicles released to the culture supernatant. The results suggest that the 75-kDa protein could be used to establish a diagnostic test specific for ovine epididymitis caused by A. seminis.

Biología molecular en micología médica / Molecular biology in medical micology

Se hace una breve revisión de las técnicas usadas en biología molecular para el estudio de los hongos en micología médica. Las técnicas genéticas utilizadas en la identificación de especies y géneros de hongos, incluyen el Polimorfismo en la longitud de los fragmentos de restricción (RFLP, Restricción Fragment Length Polymorphism) del ADNmt, la Reacción en Cadena de Polimerasa (PCR, Polimerase Chain Reaction), el análisis del polimorfismo en la longitud de los fragmentos de restricción de regiones amplificadas por (PCR-RELF), el análisis del polimorfismo en la comformación de las cadenas sencillas de ADN amplificados por PCR (PCR-SSCP), o el análisis de polimorfismo del ADN amplificado con cebadores arbitrarios (RAPD), Random Amplified Polymorphic DNA). En combinación con otros métodos como los electroforesis en geles de agarosa y transferencia a membranas de ADN (Southern Blot) o la de ARN (Northen Blot)

Detección de anticuerpos contra Haemophilus somnus en bovinos del municipio de Tuxtepec, Oaxaca, México / Detection of antibodies against Haemophilus somnus in cattle from Tuxtepec, Oaxaca, Mexico

Se buscó la identificación de anticuerpos contra Haemophilus somnus en bovinos del municipio de Tuxtepec, Oaxaca. De enero a junio de 1989, se colectaron 300 muestras séricas de bovinos clínicamente sanos seleccionados al azar, las cuales fueron procesadas mediante la prueba de Inmunodifusión en gel, por poseer una alta especificidad ante este microorganismo. Los resultados mostraron 2 por ciento de seropositividad