Augmenting the Activity of Macrolide Adjuvants against Acinetobacter baumannii.

Approximately 1.7 million Americans develop hospital associated infections each year, resulting in more than 98,000 deaths. One of the main contributors to such infections is the Gram-negative pathogen Acinetobacter baumannii. Recently, it was reported that aryl 2-aminoimidazole (2-AI) compounds potentiate macrolide antibiotics against a highly virulent strain of A. baumannii, AB5075. The two lead compounds in that report increased clarithromycin (CLR) potency against AB5075 by 16-fold, lowering the minimum inhibitory concentration (MIC) from 32 to 2 µg/mL at a concentration of 10 µM. Herein, we report a structure-activity relationship study of a panel of derivatives structurally inspired by the previously reported aryl 2-AI leads. Substitutions around the core phenyl ring yielded a lead that potentiates clarithromycin by 64- and 32-fold against AB5075 at 10 and 7.5 µM, exceeding the dose response of the original lead. Additional probing of the amide linker led to the discovery of two urea containing adjuvants that suppressed clarithromycin resistance in AB5075 by 64- and 128-fold at 7.5 µM. Finally, the originally reported adjuvant was tested for its ability to suppress the evolution of resistance to clarithromycin over the course of nine consecutive days. At 30 µM, the parent compound reduced the CLR MIC from 512 to 2 µg/mL, demonstrating that the original lead remained active against a more CLR resistant strain of AB5075.

Meridianin D analogues possess antibiofilm activity against Mycobacterium smegmatis.

The formation of bacterial biofilms significantly decreases the efficacy of antibiotic treatments. Herein, we've investigated the antibiofilm properties of the natural product meridianin D and a library of analogues against Mycobacterium smegmatis. As a result, we discovered several analogues that both inhibit and disperse M. smegmatis biofilms.

Repurposing Eukaryotic Kinase Inhibitors as Colistin Adjuvants in Gram-Negative Bacteria.

Kinase inhibitors comprise a diverse cohort of chemical scaffolds that are active in multiple biological systems. Currently, thousands of eukaryotic kinase inhibitors are commercially available, have well-characterized targets, and often carry pharmaceutically favorable toxicity profiles. Recently, our group disclosed that derivatives of the natural product meridianin D, a known inhibitor of eukaryotic kinases, modulated behaviors of both Gram-positive and Gram-negative bacteria. Herein, we expand our exploration of kinase inhibitors in Gram-negative bacilli utilizing three commercially available kinase inhibitor libraries and, ultimately, identify two chemical structures that potentiate colistin (polymyxin E) in multiple strains. We report IMD-0354, an inhibitor of IKK-ß, as a markedly effective adjuvant in colistin-resistant bacteria and also describe AR-12 (OSU-03012), an inhibitor of pyruvate dehydrogenase kinase-1 (PDK-1), as a potentiator in colistin-sensitive strains. This report comprises the first description of the novel cross-reactivity of these molecules.