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Manufacturing environment in tanning industry has been associated with human diseases caused by biological agents. This paper reports the microbiological contamination of the indoor environment at a group of tanneries in León, Guanajuato, México. The microorganisms present in the indoor environment of the tannery industry has been quantified and identified. The bacteria and fungi concentration in almost all cases exceeded the acceptable levels as dictated by Swedish standard and the limit values proposed by the American Industrial Hygiene Association. The indoor/outdoor ratio was determined, revealing poor air quality at the studied sites. This study has illustrated the presence of pathogens, hazardous to humans in indoor environments of tanneries. The identified bacteria by sequencing of 16S rDNA gene, belonged to families: Bacillaceae, Corynebacteriaceae, Enterobacteriaceae, Moraxellaceae, Nocardiopsaceae, Pseudomonadaceae, Staphylococcaceae. Some of which can be categorized as pathogens such as Acinetobacter calcoaceticus, Acinetobacter johnsonii, Nocardiopsis dassonvillei, Pantoea agglomerans, Pseudomonas putida and Staphylococcus gallinarum. In addition, Fungi genuses identified by microscopy were Aspergillus and Penicillium. The yeasts presumptively identified by ChromAgar medium were Candida krusei and Candida glabrata. Some of these identified microorganisms have been correlated with adverse human health effects, especially in individuals with immunocompromised system.

Un extracto de estigmas del híbrido de maíz A-791 fue adicionado a un medio de cultivo, evaluándose su efecto sobre el crecimiento, esporulación y síntesis de micotoxinas de Aspergillus parasiticus ATCC 16992 y A. nidulans FGSC-26. Se encontró un efecto estimulatorio en el crecimiento de ambos hongos y la esporulación del primero, contrastado con el efecto inhibitorio en la síntesis de aflatoxinas de A. parasiticus y estimulatorio en la de esterigmatocistina de A. nidulans. Los resultados sugieren la presencia de compuestos en los estigmas frescos del maíz que estimulan el crecimiento y esporulación de A. parasiticus, pero inhiben la síntesis de aflatoxinas.A silk (stigmas) extract of hybrid A-791 of maize was added to synthetic culture, evaluating its effect on growth, sporulation and synthesis of micotoxins of Aspergillus parasiticus ATCC 16992 and A. nidulans FGSC-26. It was observed a stimulatory effect in growth of both fungi and sporulation of on the first, contrasting with inhibiting effect in the synthesis of afl atoxins of A. parasiticus and stimulatory in the sterigmatocystin of A. nidulans. Results suggest the presence of compound in stigmas fresh of maize that stimulate the growth and sporulation of A. parasiticus, but inhibit the aflatoxins synthesis.

In previous communications the essential role of spermidine in Ustilago maydis was demonstrated by means of the disruption of the genes encoding ornithine decarboxylase (ODC) and spermidine synthase (SPE). However, the assignation of specific roles to each polyamine in different cellular functions was not possible because the spermidine added to satisfy the auxotrophic requirement of odc/spe double mutants is partly back converted into putrescine. In this study, we have approached this problem through the disruption of the gene-encoding polyamine oxidase (PAO), required for the conversion of spermidine into putrescine, and the construction of odc/pao double mutants that were unable to synthesize putrescine by either ornithine decarboxylation or retroconversion from spermidine. Phenotypic analysis of the mutants provided evidence that putrescine is only an intermediary in spermidine biosynthesis, and has no direct role in cell growth, dimorphic transition, or any other vital function of U. maydis. Nevertheless, our results show that putrescine may play a role in the protection of U. maydis against salt and osmotic stress, and possibly virulence. Evidence was also obtained that the retroconversion of spermidine into putrescine is not essential for U. maydis growth but may be important for its survival under natural conditions.

Interest in the bacterial protective effect against mycotoxins has greatly increased. This effect is mostly strain-dependent and the mechanisms involved are still not well understood. The objectives of this work were (1) to assess the ability of Lactobacillus casei Shirota to bind aflatoxin B1 (AFB1) by fluorescent monoclonal antibody staining, (2) to evaluate the AFB1-bacteria interaction by atomic force microscopy, and (3) to determine its effect on intestinal absorption through detection of AFB1-Lys adducts used as biological markers to a 3-week aflatoxin exposure in a murine model. The micrographs obtained in this work showed for the first time a clear visual image of the ability of Lactobacillus casei Shirota to bind AFB1 into the bacterial cell envelope. The images also revealed that aflatoxin binding produces structural changes that modify the bacterial cell surface. AFB1-Lys adducts quantified from blood samples were found to be present at significantly lower levels in animals receiving AFB1 plus bacteria than in those receiving only AFB1. This suggests that the presence of Lactobacillus casei Shirota can decrease aflatoxin absorption at the intestinal level even after a long period of toxin exposure, which consequently circumvents its toxic effects.

Aims: To assess the ability of five probiotic bacteria to bind aflatoxin B1 and to determine the key role of teichoic acids in the binding mechanism. Methods and Results: The strains were incubated in aqueous solutions containing aflatoxin B1 (AFB1). The amount of free toxin was quantified by HPLC. Stability of the bacteria–aflatoxin complex was evaluated by repeated washes with buffer. In order to understand the binding process, protoplasts, spheroplasts and cell wall components of two strains were analysed to assess their capacity to bind AFB1. Additionally, the role of teichoic acids in the AFB1 binding process was assessed. Lactobacillus reuteri strain NRRL14171 and Lactobacillus casei strain Shirota were the most efficient strains for binding AFB1. The stability of the AFB1–bacteria complex appears to be related to the binding ability of a particular strain; AFB1 binding was also pH-dependent. Our results suggest that teichoic acids could be responsible for this ability. Conclusions: Our results provide information concerning AFB1 binding by previously untested strains, leading to enhanced understanding of the mechanism by which probiotic bacteria bind AFB1. Significance and Impact of the Study: Our results support the suggestion that some probiotic bacteria could prevent absorption of aflatoxin from the gastrointestinal tract.

OBJETIVO: Confirmar el efecto de la nixtamalización tradicional sobre la aflatoxina, identificar el compuesto remanente en masa, evaluar su toxicidad y su regeneración por tratamiento ácido. MATERIAL Y MÉTODOS: Se utilizó maíz, sin y con aflatoxina, y se nixtamalizó. La toxicidad se evaluó en pollos de ocho días de edad. Se aplicó el tratamiento ácido a la masa. La cuantificación de aflatoxinas se realizó por cromatografía líquida de alta resolución (HPLC). RESULTADOS: La nixtamalización destruyó la aflatoxina (96%) y el aflatoxicol (70%); el remanente en masa fue aflatoxina B1. El tratamiento ácido in vitro no eleva las concentraciones de ninguna de las dos micotoxinas. Los pollos murieron al ingerir 260 mg de AFB1, y la masa con aflatoxina remanente no fue tóxica. CONCLUSIONES: Los resultados ilustran el beneficio de la nixtamalización tradicional en la inactivación de las aflatoxinas presentes en maíz y en su no reconstitución por efecto del tratamiento ácido.OBJECTIVE: To ratify the effect of traditional "nixtamalización" upon aflatoxin in corn, to identify the residual compound in dough, to evaluate its toxicity, and to verify the effect of acidic treatment on the regeneration of aflatoxin. MATERIAL AND METHODS: Corn with and without aflatoxin was treated separately with lime and heat to obtain two types of dough. Aflatoxin and the residual compound were quantified by high pressure liquid chromatography (HPLC) and toxicity was evaluated in eight day old chicks. RESULTS: "Nixtamalización" destroyed AFB1 (96%) and aflatoxicol (70%). The residual compound was identified as AFB1. Experimental animals died by ingestion of 260 mg of AFB1 Dough containing residual aflatoxin was not toxic. Acidic. treatment did not increase aflatoxin concentration, nor aflatoxicol. CONCLUSIONS: The results support the use of traditional "nixtamalización" as a means to inactivate aflatoxin in corn and that acidic treatment prevents its regeneration in dough.

We analyzed the regulation of sterigmatocystin biosynthesis in wild type and mutant strains of Emericella nidulans (= Aspergillus nidulans). A positive correlation between both asexual and sexual sporulation and synthesis of the mycotoxin was observed. Those conditions which favored sporulation stimulated sterigmatocystin formation, and vice versa. Both processes were stimulated by light in a + genetic background. In contrast, they were inhibited by diaminobutanone, an inhibitor of ornithine decarboxylase. The effect of this inhibitor was partially reverted by putrescine addition. Partial supplementation of specific requirements to auxotrophic mutants allowed normal vegetative growth, but interfered with asexual sporulation and sterigmatocystin biosynthesis. Synthesis of the mycotoxin was neither affected in a brlA mutant or in developmental mutants blocked at later steps in sporulation. As in wild type strain, diaminobutanone inhibited sterigmatocystin biosynthesis and cleisthotecia formation in the brlA mutant, and its effect was reverted by addition of putrescine. The inhibitor also affected the transcription of brlA. Our results indicate that sporulation and the synthesis of sterigmatocystin are co-regulated at a step previous to the brlA execution point.

Regulation of aflatoxin biosynthesis during differentiation ofAspergillus parasiticuswas analyzed by using a drug that inhibits the development of the fungus and mutants affected in sporulation. Diaminobutanone, a competitive inhibitor of ornithine decarboxylase, repressed spore germination. If added after spore germination had occurred, it blocked sporulation completely and suppressed aflatoxin biosynthesis, but was only partially inhibitory of mycelial growth. Putrescine partially counteracted the inhibitory effect of the drug on both sporulation and aflatoxin biosynthesis. Analysis of mutants affected in sporulation confirmed the existence of a relationship between sporulation and aflatoxin formation. A nonsporulating mutant was unable to synthesize aflatoxins. In a sectorial mutant, the sporulating sector synthesized aflatoxins normally, whereas the asporogenous sector was unable to do so. It is suggested that regulation of aflatoxin biosynthesis is correlated with the sporulation process.

In previous communications the essential role of spermidine in Ustilago maydis was demonstrated by means of the disruption of the genes encoding ornithine decarboxylase (ODC) and spermidine synthase (SPE). However, the assignation of specific roles to each polyamine in different cellular functions was not possible because the spermidine added to satisfy the auxotrophic requirement of odc/spe double mutants is partly back converted into putrescine. In this study, we have approached this problem through the disruption of the gene-encoding polyamine oxidase (PAO), required for the conversion of spermidine into putrescine, and the construction of odc/pao double mutants that were unable to synthesize putrescine by either ornithine decarboxylation or retroconversion from spermidine. Phenotypic analysis of the mutants provided evidence that putrescine is only an intermediary in spermidine biosynthesis, and has no direct role in cell growth, dimorphic transition, or any other vital function of U. maydis. Nevertheless, our results show that putrescine may play a role in the protection of U. maydis against salt and osmotic stress, and possibly virulence. Evidence was also obtained that the retroconversion of spermidine into putrescine is not essential for U. maydis growth but may be important for its survival under natural conditions.

All food used for human and animal consumption should be free of contaminants, the result of which would be the elimination or reduction of diseases, intoxication and even death (FAO 2002). Economic losses also would be avoided (Cardwell et al. 2001). Several strategies such as preventing contamination during food production, processing and storage should be strictly adhered to in order to achieve these objectives. In the case of natural contaminants such as the mycotoxins (International Agency for Research on Cancer 2002), which are substances produced by fungi in grains and food, detoxification has been the main strategy without full success. The destruction of aflatoxin B1 (AFB1) that is contained in cereals and oil seeds for human and animal consumption has been pursued since its discovery in 1960 when it was found in Brazilian peanuts (Goldblatt 1968). The AFB1 has a positive correlation with hepatic cancer, acute and chronic intoxication, and death in humans and animals (Azziz-Baumgartner et al. 2005). Kwashiorkor and Reye's syndrome diseases in children also have been related to the ingestion of AFB1 (Task Force Report 2003).

The presence of AFB1 in human beings was detected in Mexico in 1996 both as a mutation of the gene p53 in hepatocellular carcinomas in Monterrey, Mexico, and as the adduct AFB1-lysine in serum from patients in Matamoros, Mexico in 2003. Aflatoxin B1 has been classified as a carcinogenic agent to humans by the International Agency for Research on Cancer. The compound is a natural contaminant produced by Aspergillus flavus and/or A. parasiticus when these fungi grow on different food products. At the molecular level, this review covers the carcinogenic, mutagenic and toxic properties of these mycotoxins and their risk to humans. It also gives insight into the causal relationship between aflatoxins and hepatocellular carcinoma. Information is provided about AFB1-formamidopyrimidine, which is a determinant of the carcinogenic and mutagenic capabilities. The results suggest that the Mexican population ingests food containing low amounts of AFB1. Analyses is presented of AFB1 toxicity, which is a consequence of the carcinogenic activity in liver cells.

Un extracto de estigmas del híbrido de maíz A-791 fue adicionado a un medio de cultivo, evaluándose su efecto sobre el crecimiento, esporulación y síntesis de micotoxinas de Aspergillus parasiticus ATCC 16992 y A. nidulans FGSC-26. Se encontró un efecto estimulatorio en el crecimiento de ambos hongos y la esporulación del primero, contrastado con el efecto inhibitorio en la síntesis de aflatoxinas de A. parasiticus y estimulatorio en la de esterigmatocistina de A. nidulans. Los resultados sugieren la presencia de compuestos en los estigmas frescos del maíz que estimulan el crecimiento y esporulación de A. parasiticus, pero inhiben la síntesis de aflatoxinas.

Aflatoxins are potent mutagenic and carcinogenic compounds produced by some strains of Aspergillus flavus, A. nomius, and A. parasiticus that are commonly present in the environment. Human populations, particularly those whose basic diet includes grains, are in risk to exposure to aflatoxins. It is thus necessary to monitor and control the contamination of food and feed by aflatoxins in both domestic and international trade. As large amounts of corn are imported into Mexico from the United States, this paper stresses the need to develop legislation and enforce standards to ensure trade of corn with the minimal amount of aflatoxin.

To ratify the effect of traditional "nixtamalización" upon aflatoxin in corn, to identify the residual compound in dough, to evaluate its toxicity, and to verify the effect of acidic treatment on the regeneration of aflatoxin.Corn with and without aflatoxin was treated separately with lime and heat to obtain two types of dough. Aflatoxin and the residual compound were quantified by high pressure liquid chromatography (HPLC) and toxicity was evaluated in eight day old chicks."Nixtamalización" destroyed AFBI (96%) and aflatoxicol (70%). The residual compound was identified as AFBI. Experimental animals died by ingestion of 260 microg of AFBI Dough containing residual aflatoxin was not toxic. Acidic treatment did not increase aflatoxin concentration,nor aflatoxicol.The results support the use of traditional "nixtamalización" as a means to inactivate aflatoxin in corn and that acidic treatment prevents its regeneration in dough.

Objective. To ratify the effect of traditional “nixtamalizacion” upon aflatoxin in corn, to identify the residual compound in dough, to evaluate its toxicity, and to verify the effect of acidic treatment on the regeneration of aflatoxin. Material and Methods. Corn with and without aflatoxin was treated separately with lime and heat to obtain two types of dough. Aflatoxin and the residual compound were quantified by high pressure liquid chromatography (HPLC) and toxicity was evaluated in eight day old chicks. Results. “Nixtamalizacion” destroyed AFB1 (96%) and aflatoxicol (70%). The residual compound was identified as AFB1. Experimental animals died by ingestion of 260 ∝g of AFB1 . Dough containing residual aflatoxin was not toxic. Acidic treatment did not increase aflatoxin concentration, nor aflatoxicol. Conclusions. The results support the use of traditional “nixtamalizacion” as a means to inactivate aflatoxin in corn and that acidic treatment prevents its regeneration in dough.

Bucio-Villalobos, C.M., Peña-Cabriales, J.J. y Guzmán-de-Peña,D. 2001. Producción de Aflatoxinas en Maíz in vitro. Revista Mexicana de Fitopatología 19:218-222.El maíz en México, fundamentalmente para consumo humano,es almacenado durante tiempos variables y en diversas condiciones ambientales que favorecen la infestación pori nsectos y hongos. La capacidad toxigénica de estos últimos determina el interés de conocer su comportamiento durante el almacenamiento. En el presente estudio se determinó elefecto de la temperatura, la concentración de inóculo y la integridad del grano sobre la síntesis de aflatoxinas por Aspergillus parasiticus en tres híbridos de maíz bajo condiciones simuladas de almacenamiento. Se utilizaron tres híbridos de maíz con infección natural y artificial en el campoy reinoculados en el laboratorio, y se sometieron a 27 y 33°Cdurante el almacenamiento. Los resultados indicaron que: 1)Fusarium sp. fue el hongo predominante en la infestación natural y A. parasiticus en la artificial; 2) Los niveles de aflatoxinas se incrementaron en ambas temperaturas de almacenamiento; 3) A mayor inóculo de A. parasiticus mayor cantidad de aflatoxinas; y 4) Los niveles de aflatoxinas fueronmenores a 33°C cuando el hongo predominante fue Fusariumsp. Estos resultados ilustran la importancia de la carga de laspoblaciones fúngicas y la temperatura durante el almacenamiento en la síntesis de aflatoxinas en el maíz. Sesugiere realizar prácticas de limpieza del grano y almacenamiento en lugares secos y con baja temperatura parareducir (o evitar) la síntesis de aflatoxinas

Fusarium proliferatum, F. subglutinans, and F. verticillioides are known causes of ear and kernel rot in maize worldwide. In Mexico, only F. verticillioides and F. subglutinans, have been reported previously as causal agents of this disease. However, Fusarium isolates with different morphological characteristics to the species that are known to cause this disease were obtained in the Highland-Valley region of this country from symptomatic and symptomless ears of native and commercial maize genotypes. Moreover, while the morphological studies were not sufficient to identify the correct taxonomic position at the species level, analyses based in the Internal Transcribed Spacer region and the Nuclear Large Subunit Ribosomal partial sequences allowed for the identification of F. subglutinans, F. solani, and F. verticillioides, as well as four species (F. chlamydosporum, F. napiforme, F. poae, and F. pseudonygamai) that had not previously been reported to be associated with ear rot. In addition, F. napiforme and F. solani were absent from symptomless kernels. Phylogenetic analysis showed genetic changes in F. napiforme, and F. pseudonygamai isolates because they were not true clones, and probably constitute separate sibling species. The results of this study suggest that the biodiversity of Fusarium species involved in ear rot in Mexico is greater than that reported previously in other places in the world. This new knowledge will permit a better understanding of the relationship between all the species involved in ear rot disease and their relationship with maize.