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To our knowledge, this is the first work on drug susceptibility patterns of rapid growing mycobacteria from Latin America. The susceptibility patterns for 14 antimicrobial agents of the three most important species that cause skin infections in Venezuela were determined as follows: 63 strains belonging to Mycobacterium abscessus group, 66 strains of the Mycobacterium fortuitum group, and 13 Mycobacterium chelonae strains. The M. abscessus group strains were resistant to most antibiotics tested while M. fortuitum strains were relatively susceptible to a large number of antibiotics. We demonstrate the presence of an inducible and truncated erm(41) gene in M. abscessus group, namely M. abscessus subsp. massiliense. We show the variations in susceptibility to antimicrobial agents within and between the mycobacterial species and compare our susceptibility patterns with those reported from other countries. We conclude that the identification of mycobacteria to the species level can guide the antibiotic treatment, but that it is always important to consider drug susceptibility testing when rapidly mycobacteria are isolated.

Myrosinase (β-thioglucosidase glucohydrolase, EC 3.2.1.147) from broccoli (Brassica oleracea var. italica) was purified by ammonium sulfate precipitation followed by concanavalin A affinity chromatography, with an intermediate dialysis step, resulting in 88% recovery and 1318-fold purification. These are the highest values reported for the purification of any myrosinase. The subunits of broccoli myrosinase have a molecular mass of 50-55 kDa. The native molecular mass of myrosinase was 157 kDa, and accordingly, it is composed of three subunits. The maximum activity was observed at 40 °C and at pH below 5.0. Kinetic assays demonstrated that broccoli myrosinase is subjected to substrate (sinigrin) inhibition. The Michaelis-Menten model, considering substrate inhibition, gave Vmax equal to 0.246 μmol min(-1), Km equal to 0.086 mM, and K(I) equal to 0.368 mM. This is the first study about purification and characterization of broccoli myrosinase.

Thallium acetate in concentrations of 500 to 1000 mg/l is tolerated in the culture by the most mollicutes of the orders Mycoplasmatales and Acholeplasmatales and by this reason it is added in the culture media as a selective element for the detection and propagation of mycoplasmas and acholeplasmas. Because of the high toxicity of thallium acetate and its accumulation in the environment, thallium acetate is not biodegradable, an alternative was searched. The results and analysis of tests with nine mollicute species are presented here. It is recommended to replace thallium acetate in the formulations where it is used and colistin sulfate is proposed as its substitute.