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The nephrotoxic and carcinogenic mycotoxin ochratoxin A (OTA) is a worldwide contaminant in food commodities and also found frequently in human biological fluids. Dietary contaminants ingested by nursing mothers can appear in breast milk. But the rate of lactational transfer of OTA has not been investigated so far at various stages of breastfeeding. Therefore, and to investigate OTA exposure of Chilean infants, we conducted a longitudinally designed study in mother-child pairs (n = 21) with parallel collection of maternal blood, milk and of infant urine samples over a period of up to 6 months. Validated analytical methods were applied to determine OTA concentrations in all biological samples (n = 134). OTA was detected in almost all maternal blood plasma, at concentrations ranging between 72 and 639 ng/L. The OTA concentrations in breast milk were on average one quarter of those measured in plasma (M/P ratio 0.25). Interestingly, a higher fraction of circulating OTA was excreted in colostrum (M/P 0.4) than with mature milk (M/P ≤ 0.2). Infants exposure was calculated as daily intake from our new data for OTA levels in breast milk, and taking into account milk consumption and body weight as additional variables: Chilean infants have an average intake of 12.7 ± 9.1 ng/kg bw during the first 6 days after delivery while intake with mature milk results in average values close to 5.0 ng/kg bw/day. Their OTA exposure is discussed in the context of tolerable intake values suggested by different scientific bodies. Moreover, the study design enabled a comparison of OTA intake and infant urine concentrations over the breastfeeding period. The statistical analysis of n = 27 paired values showed a good correlation (r = 0.57) for this type of studies and thereby confirms that urinary OTA analysis in infants is a valid biomarker of exposure.

In this study, arsenic resistant bacteria were isolated from sediments of an arsenic contaminated river. Arsenic tolerance of bacteria isolated was carried out by serial dilution on agar plate. Redox abilities were investigated using KMnO4. arsC and aox genes were detected by PCR and RT-PCR, respectively. Bacterial populations were identified by RapID system. Forty nine bacterial strains were isolated, of these, 55 % corresponded to the reducing bacteria, 4% to oxidizing bacteria, 8% presented both activities and in 33% of the bacteria none activity was detected. arsC gene was detected in 11 strains and aox genes were not detected. The activity of arsenic transforming microorganisms in river sediment has significant implications for the behavior of the metalloid.

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Yeasts can adapt to a wide range of pH fluctuations (2 to 10), while Helicobacter pylori, a facultative intracellular bacterium, can adapt to a range from pH 6 to 8. This work analyzed if H. pylori J99 can protect itself from acidic pH by entering into Candida albicans ATCC 90028. Growth curves were determined for H. pylori and C. albicans at pH 3, 4, and 7. Both microorganisms were co-incubated at the same pH values, and the presence of intra-yeast bacteria was evaluated. Intra-yeast bacteria-like bodies were detected using wet mounting, and intra-yeast binding of anti-H. pylori antibodies was detected using immunofluorescence. The presence of the H. pylori rDNA 16S gene in total DNA from yeasts was demonstrated after PCR amplification. H. pylori showed larger death percentages at pH 3 and 4 than at pH 7. On the contrary, the viability of the yeast was not affected by any of the pHs evaluated. H. pylori entered into C. albicans at all the pH values assayed but to a greater extent at unfavorable pH values (pH 3 or 4, p = 0.014 and p = 0.001, respectively). In conclusion, it is possible to suggest that H. pylori can shelter itself within C. albicans under unfavorable pH conditions.

The mycotoxin ochratoxin A (OTA) and its metabolite ochratoxin alpha (OTα) were determined in milk and blood from nine lactating women who provided samples soon after delivery at a hospital in southern Chile. The analytical method applied liquid-liquid extraction with chloroform, and in the case of blood, an extra purification with solid phase extraction prior to HPLC analysis with fluorescence detection. OTA was detected in all human milk samples, with an average concentration of 106 ± 45 ng/L (range 44-184 ng/L). Levels of OTα were 40 ± 30 ng/L (LOQ 40 ng/L), but increased considerably upon enzymatic hydrolysis with ß-glucuronidase/sulfatase (up to 840 ± 256 ng/L) in human milk. By contrast, there was no evidence for conjugates of OTA. The data on OTA in breast milk and levels reported in blood from women in Chile are indicative of an efficient lactational transfer of the mycotoxin. Infant exposure to OTA was estimated by considering their daily OTA intake with human milk at early stages of nursing. For the majority of milk samples, the calculated OTA intake of infants exceeded the tolerable daily intake (TDI) of 5 ng/kg body weight (bw)/day proposed by the Nordic Expert Group, and infant exposure approached the provisional tolerable doses of 14-16 ng/kg bw/day suggested by the Joint FAO/WHO Expert Committee on Food Additives (JEFCA) and by EFSA for adults. The present study documents and confirms the presence of OTA in human milk at levels where the TDI can be exceeded. These results point out the need to continue food and biological monitoring and to develop strategies, e.g. dietary recommendations to pregnant and lactating women, aimed to reduce OTA exposure in early periods of life.

In Northern Chile, high arsenic concentrations are found in natural water, both natural and anthropogenic sources, a significant health risk. Nine bacterial strains were isolated from Camarones river sediments, located in Northern Chile, a river showing arsenic concentrations up to 1,100 microg/L. These strains were identified as Pseudomonas and they can oxidize arsenite (As(III)) to the less mobile arsenate (As(V)). The arsenite oxidase genes were identified in eight out of nine isolates. The arsenite oxidizing ability shown by the nine strains isolated from arsenic enriched sediments open the way to their potential application in biological treatment of effluents contaminated with arsenic.

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