Levedura antagonista no controle de fungos filamentosos deteriorantes de alimentos / Antagonistic yeast against deteriorating mold of food

Este trabalho avaliou o efeito antifúngico in vitro de toxina killer de Hansenula wingei contra Aspergillus ochraceus e Penicillium expansum deteriorantes de alimentos. O extrato livre de células-ELC contendo a toxina killer (obtido a partir do cultivo da levedura em Caldo MPL a 25ºC/96 horas) foi submetido ao ensaio antifúngico por meio de análise microscópica, determinando-se a porcentagem de germinação conidial e o desenvolvimento de hifas dos fungos testados. H. wingei inibiu a germinação conidial de A. ochraceus e P. expansum em 98,91% e 96,49%, respectivamente, bem como a inibição do desenvolvimento micelial de ambos os fungos foi maior que 78%. O composto antifúngico mostrou-se estável ao tratamento térmico de 90ºC/30 min., indicando a possibilidade de aplicação no biocontrole in situ de frutos pós-colheita.

Ochratoxin A, citrinin and deoxynivalenol decrease claudin-2 expression in mouse rectum CMT93-II cells.

Intestinal epithelial cells are the first targets of ingested mycotoxins, such as ochratoxin A, citrinin and deoxynivalenol. It has been reported that paracellular permeability regulated by tight junctions is modulated by several mycotoxins by reducing the expression of specific claudins and integral membrane proteins in cell-cell contacts, accompanied by increase in phosphorylation of mitogen-activated protein kinases, including extracellular signal-related kinase (ERK) 1/2, p38 and c-Jun NH2-terminal protein kinase. Claudin-2 is expressed in the deep crypt cells, but not in the villus/surface cells in vivo. While Caco-2, T84 and IPEC-J2 cells, which are widely used intestinal epithelial cell lines to assess the influence of mycotoxins, do not express claudin-2, CMT93-II cells express claudin-2. We previously reported that inhibition of the ERK pathway reduced claudin-2 levels in cell-cell contacts in CMT93-II cells. In this study, we examined whether ochratoxin A, citrinin and deoxynivalenol affect claudin-2 expression and ERK1/2 phosphorylation in CMT93-II cells. We found that all mycotoxins reduced claudin-2 expression in cell-cell contacts, with reduction (by citrinin and deoxynivalenol) or no change (by ochratoxin A) in phosphorylated ERK1/2. All mycotoxins increased transepithelial electrical resistance, but did not affect flux of fluorescein. While ochratoxin A and citrinin are known to be nephrotoxic, only deoxynivalenol reduced claudin-2 expression in MDCK II cells derived from the renal tubule. These results suggest that claudin-2 expression is regulated not only by the ERK pathway, but also by other pathways in an organ-specific manner.

Occurrence of fungi and cytotoxicity of the species: Aspergillus ochraceus, Aspergillus niger and Aspergillus flavus isolated from the air of hospital wards.

OBJECTIVES: The basic care requirement for patients with weakened immune systems is to create the environment where the risk of mycosis is reduced to a minimum. MATERIAL AND METHODS: Between 2007 and 2013 air samples were collected from various wards of a number of hospitals in Kraków, Poland, by means of the collision method using MAS-100 Iso MH Microbial Air Sampler (Merck Millipore, Germany). The air mycobiota contained several species of fungi, and almost 1/3 of it was made up of the species of the Aspergillus genus. Sixty-one strains of species other than A. fumigatus were selected for the research purposes, namely: 28 strains of A. ochraceus, 22 strains of A. niger and 11 strains of A. flavus species. Selected fungi underwent a cytotoxicity evaluation with the application of the MTT colorimetric assay (3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide). The assay assesses cell viability by means of reducing the yellow tetrazolium salt to insoluble formazan. A semi-quantitative scale for cytotoxicity grading was adopted: low cytotoxic effect (+) with half maximal inhibitory concentration (IC50) for values ranging from 31.251 cm2/ml to 7.813 cm2/ml, medium cytotoxic effect (++) for values ranging from 3.906 cm2/ml to 0.977 cm2/ml and the high one (+++) for values ranging from 0.488 cm2/ml to 0.061 cm2/ml. The absence of cytotoxicity was determined when the IC50 values was at ≥ 50. RESULTS: For 48 samples the analyzed fungi displayed the cytotoxic effect with A. ochraceus in 26 out of 28 cases, with 11 strains displaying the high cytotoxic effect. The lowest cytotoxicity was displayed by fungi of A. niger in 13 out of 22 cases, and the major fungi of A. flavus species were toxic (9 out of 11 cases). CONCLUSIONS: A half of the fungi displayed the low cytotoxic effect. On the basis of the comparison of average cytotoxicity levels it was determined that there were significant differences in the levels of cytotoxicity of the analyzed fungi. However, such statement may not provide grounds for a definite conclusion about the compared species of fungi that display a more cytotoxic effect than others. Int J Occup Med Environ Health 2017;30(2):231-239.

Occurrence of ochratoxin A and ochratoxigenic mycoflora in corn and corn based foods and feeds in some South American countries.

Cereals and cereal- derived products constitute the base of human and animal feeding in South American countries. This review attempts to give an overview of the ochratoxin A (OTA) occurrence and potential sources of OTA contamination in those products. The environmental conditions as humidity and temperature in the colonization of the substrates by Aspergillus section Nigri isolated from corn kernels were also discussed. The available information on the ochratoxigenic mycoflora and OTA presence in corn, corn based food and feed is limited. Only few surveys have been carried out in Argentina, Ecuador and Brazil; which showed that Aspergillus niger aggregate and A. ochraceus species would be the main source of OTA. It's possible to emphasize that, the species A. carbonarius has not been isolated from these substrates and Penicillium verrucosum was isolated only from pig feeds of Argentinean samples in low percentage. Studies about the ecophysiology of ochratoxigenic fungi and OTA occurrence are in progress in Latin America to reduce the impact of this toxin in the food chain.

Experimental one year ochratoxin A toxicosis in pigs.

Mild mycotoxic nephropathy was induced in 6 pigs by a diet containing ochratoxin A at 800 ppb, several times higher than that naturally encountered in some feed for pig production in Bulgaria. The nephropathy was expressed only as slightly hypertrophied kidneys with a faintly mottled surface, discernible at the end of the experiment to a skilled observer but probably not recognisable in routine slaughterhouse processing. Histological examination showed two types of changes: degenerative - affecting epithelial cells in some proximal tubules of pigs after 6 months, and proliferative changes in the interstitium which predominated after 1 year of exposure to ochratoxin A. Telangiectasis and lymph stasis were rarely seen. The renal lesions were similar to those described for classical mycotoxic porcine nephropathy formerly encountered in Denmark, but they were rather different from the porcine nephropathy which occurs spontaneously in Bulgaria. Measurement of ochratoxin A in serum provided analytical values complementary to feed intake and with similar concentration values. It also showed both accumulation with time, from 3 months to 6 months (approximately 1 ppm), and a 2-fold range of values within a group eating from a common feed source, as in commercial pig production. Mild symptomatology in this long, single-mycotoxin experiment serves to lessen somewhat the current perception of the direct renal toxicity of ochratoxin A alone, though a role in multi-toxin contexts is unquestioned.

Experimental mycotoxic nephropathy in pigs provoked by a diet containing ochratoxin A and penicillic acid.

Mycotoxic nephropathy was induced in 18 young pigs by diets contaminated with strains of Aspergillus ochraceus containing ochratoxin A (OTA) and penicillic acid (PA) at levels corresponding to those naturally encountered in animal feeds in Bulgaria. Haematological and biochemical parameters, as well as the morphological and ultrastructural changes in various internal organs, and especially in the kidneys, were examined at different stages of development of the disease. A mottled surface of the kidneys was only seen in pigs exposed to a mouldy diet containing 180 ppb OTA for 3 months, but microscopic lesions, as well as changes in various haematological and biochemical parameters, were observed in all groups exposed to the same mouldy diet containing only 90 or 180 ppb OTA. Histological examination showed two types of change: degenerative changes affecting the epithelial cells of the proximal tubules, which predominated at the initial stage, and proliferative changes in the interstitium, which predominated at the later stage of the disease. Telangiectasis and lymph stasis were also seen, as well as degenerative changes in the capillary endothelium. The characteristic renal lesions were similar to those observed in spontaneous cases of mycotoxic porcine nephropathy in Bulgaria, but they were a little different from the classic Danish porcine nephropathy. The enhanced toxicity of OTA in our study may be due to a synergistic effect between OTA and PA or to some other unknown metabolites produced by the same ochratoxinogenic strains of A. ochraceus.