Drug discovery to reverse clarithromycin resistance in multidrug-resistant mycobacterium abscessus

Abstract

Mycobacterium abscessus is an emerging life-threatening non-tuberculous mycobacterium with extensive drug-resistance mechanisms. M. abscessus infections have been causing substantial economic burden, due to the lengthy treatment lasting up to 24 months with multi-drug regimens. Despite this extensive treatment, M. abscessus infections still remain incurable. Thus, instead of developing new antibiotics, our objective is to identify an adjuvant that can be employed together with clarithromycin, its first-line treatment, to reverse clarithromycin resistance in M. abscessus. Clarithromycin resistance in M. abscessus is conferred by inducible erythromycin ribosome methylase (Erm) 41 enzyme. We first developed an optimized and novel induction protocol to induce clarithromycin resistance in M. abscessus, suitable for low cost and high-throughput drug screening. Two-stage screening was then used to screen nearly 2,200 compounds against resistant M. abscessus at single concentration (20 μM). Hits were validated as potential clarithromycin adjuvant in dose-response and checkerboard assay. Three promising adjuvant candidates were identified with good clarithromycin potentiation activity, with two have been validated to exert synergistic effect with clarithromycin while demonstrating negligible inhibition when used alone. Our approach of antibiotic adjuvant employing novel clarithromycin induction drug screening assay pave promising path to M. abscessus drug discovery and development.