Targeting homologous recombination repair to potentiate fluoroquinolone efficacy in Mycobacterium abscessus

Impact statement Fluoroquinolones (FQs) are important for treating fast‐growing mycobacterial infections; however, their efficacy can be limited by intrinsic resistance and the emergence of acquired resistance. FQs induce lethal DNA double‐strand breaks (DSBs) by targeting topoisomerases. Through a transposon screen in Mycobacterium abscessus , we identified that disruption of adnB , a homologous recombination (HR) gene, markedly sensitized the pathogen to FQs. Subsequent study showed that deleting core HR components ( adnB , recO , recA , recR , and ruvB ) increased FQs' susceptibility, while other DSB repair pathways (single‐strand annealing or non‐homologous end joining) had no effect, demonstrating a unique reliance on HR for FQs' tolerance. Complementation with native or its homolog genes restored the resistance phenotype, indicating a conserved HR‐dependent tolerance mechanism in M . abscessus . In a murine model, genetic HR abrogation significantly improved FQs' therapeutic efficacy. These results highlight HR repair as a potential therapeutic target to potentiate FQs' activity and combat drug resistance in M . abscessus infections.