Polymyxins retain activity and efficacy against "resistant" strains when tested in physiological conditions.

The emergence of plasmid-mediated resistance threatens the efficacy of polymyxins as the last line of defense against pan-drug-resistant infections. However, we have found that using Mueller-Hinton II (MHII), the standard minimum inhibitory concentration (MIC) medium, results in MIC data that are disconnected from treatment outcomes. We found that culturing putative colistin-resistant clinical isolates, as defined by MICs of >2 mg/L in standard MHII testing conditions, in bicarbonate-containing media reduced MICs to the susceptible range by preventing colistin resistance-conferring lipopolysaccharide modifications from occurring.

Near real-time determination of metabolic parameters for unquenched 6-mercaptopurine and xanthine oxidase samples using capillary electrophoresis.

The enzyme activity of xanthine oxidase (XO) is influenced by several environmental factors including solution conditions, storage conditions, inhibitors, other enzymes, and activators. For instance, the metabolic reaction involving XO and the pro-drug 6-mercaptopurine, a drug used in the treatment maintenance of acute lymphatic leukemia, Crohn's disease, and ulcerative colitis, is often modified through the use of inhibitors, which varies the kinetic parameters associated with this reaction. Methods that provide fast and accurate determination of these kinetic constants can help in understanding the mechanism of these reactions.