Metal-based antimicrobial strategies against intramacrophage Mycobacterium tuberculosis.

The combinatorial chemistry has been an important tool for the development of new strategies against the Mycobacterium tuberculosis. Therefore, we evaluated the antimycobacterial activity of two coordinated metal complexes (Cu(II) and Co(II)) and a free ligand, including in the intramacrophage environment. The complexes were more active than the free ligand, indicating that the complexation favoured the antimicrobial activity. None of the compounds showed cytotoxic effect at the concentration of 200 µg ml-1 and both complexes showed intracellular antimicrobial activity, with results as effective as rifampicin. In this study, it was possible to identify complexes containing benzohydroxamate associated with transition metal ions (Cu2+ and Co2+ ), which were able to inhibit the growth of M. tuberculosis, including in persistence stage. In addition, the docking analysis allows inferring a possible interaction of the metal complexes with the enzyme urease, which has been reported as crucial for the bacillus survival in the intraphagosomal environment. Thus, these set of results demonstrate the potential of these metals in the development of new drugs against M. tuberculosis. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, it was possible to identify complexes containing benzohydroxamate associated with transition metals (Cu2+ and Co2+ ), which were able to inhibit the growth of Mycobacterium tuberculosis, including in the persistence stage. In this context, cobalt and copper can be scaffolds for new drugs against M. tuberculosis.

Effects of different sources of Saccharomyces cerevisiae biomass on milk production, composition, and aflatoxin M1 excretion in milk from dairy cows fed aflatoxin B1.

The aim of the present study was to evaluate the effect of different sources of Saccharomyces cerevisiae (SC) biomass (20.0 g/d) obtained from sugarcane (cell wall, CW; dried yeast, DY; autolyzed yeast, AY) and the beer industry (partially dehydrated brewery yeast, BY) on milk production, fat and protein percentages, and aflatoxin M1 (AFM1) excretion in milk from dairy cows receiving 480 µg aflatoxin B1 (AFB1) per day. A completely randomized design was used with 2 lactating cows assigned to each of 10 dietary treatments, as follows: negative controls (no AFB1 or SC-based biomass), positive controls (AFB1 alone), DY alone, DY + AFB1, BY alone, BY + AFB1, CW alone, CW + AFB1, AY alone, and AY + AFB1. The cows in the aflatoxin treatment group received AFB1 from d 1 to 6, while the SC biomass was administered with the AFB1 bolus from d 4 to 6. Aflatoxin B1 or SC-based products did not affect milk production or milk composition during the experimental period. Aflatoxin M1 was detected in the milk from all aflatoxin treatment group cows, reaching maximum levels at d 3 and varying from 0.52 ± 0.03 to 1.00 ± 0.04 µg/L. At end of the treatment period, CW, AY, DY, and BY removed 78%, 89%, 45%, and 50% of AFM1 from the milk, respectively, based on the highest level found on d 3. Results indicate a potential application of industrial fermentation by-products, especially CW and AY, as a feed additive in the diets of dairy cows to reduce the excretion of AFM1 in milk.