IDENTIFYING GENOTYPIC AND PHENOTYPIC PATHS LEADING TO HIGH-LEVEL RESISTANCE FOR A RANGR OF ANTIBIOTICS

Antibiotic resistance is a growing public health concern, drawing attention to multidrug treatments. Works on resistance evolution at fixed drug concentrations or small population sizes often reveal only one or few adaptive steps. However, multi-step genotypic pathways that lead to high-level resistance are not systematically studied. To understand the multi-step genotypic pathways to high-level resistance for major drug classes, we employ our new device: the Microbial Evolution and Growth Arena (MEGA-plate). It is a giant agar plate presenting a logarithmically increasing gradient of antibiotics. The MEGA-plate allows us to track the spreading of multiple bacterial lineages as they migrate and evolve on the plate. By whole-genome sequencing of clones sampled from all over the MEGA-plate we can reveal distinct and common genomic paths to high-level resistance.
This enables us to build a comprehensive map, for each major drug class, showing the ensemble of phenotypic and genotypic mutational paths leading to high-level resistance, as well as the extent of their reproducibility and predictability.