E-Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2021

Disruption of double-strand break repair is a universal approach for combating antibiotic resistance and tolerance (#253)

Sarah A Revitt-Mills 1 2 , Elizabeth K Wright 1 2 , Madaline Vereker 1 2 , Callum O'Flaherty 1 2 , Fairley McPherson 1 2 , Catherine Dawson 1 2 , Antoine M van Oijen 1 2 , Andrew Robinson 1 2
  1. Molecular Horizons Institute and School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, New South Wales, Australia
  2. Illawarra Health and Medical Research Institute, Wollongong, New South Wales, Australia

Antimicrobial resistance (AMR) poses a potentially catastrophic threat to public health in Australia and globally. Promisingly, antibiotic-resistant bacteria have an Achilles heel: many rely on DNA repair processes to survive antibiotic treatment.

Our recent work has revealed that inactivation of double-strand break (DSB) repair (via recA and recB mutations) significantly enhances the killing of both ciprofloxacin-sensitive (CipS) and ciprofloxacin-resistant (CipR) Escherichia coli following antibiotic treatment (Minimum inhibitory concentrations (MICs) [mg/ml] CipS background: rec+ 0.014 ± 0.005; ΔrecA 0.0006 ± 0.001; ΔrecB 0.001 ± 0.001. MICs [mg/ml] CipR background: rec+ 9.2 ± 2.7; ΔrecA 1.5 ± 0.9; ΔrecB 1.6 ± 0.9). Further, repair-deficient strains were unable to induce the SOS response – a stress response that elevates rates of mutation. Disrupting DSB repair also produced potentiating effects with other bactericidal antibiotics. Sensitivity to nitrofurantoin was significantly increased (MICs [mg/ml] NitS background: rec+ 19 ± 3; ΔrecA 1 ± 0.3; ΔrecB 10 ±1. MICs [mg/ml] NitR background: rec+ 40 ± 5; ΔrecA 20 ± 3; ΔrecB 15 ± 4). Tolerance to ampicillin (defined by re-growth on a TD-test) was decreased in both sensitive and resistant backgrounds. Cell clearing by trimethoprim and kanamycin was improved in both sensitive and resistant backgrounds. SOS was reduced, or eliminated, in cells exposed to nitrofurantoin or trimethoprim (SOS undetectable in ampicillin or kanamycin-treated cells).

This work has demonstrated that DSB repair is linked to pathways that regulate mutagenesis (the SOS response). Would disrupting DSB repair actually slow down the evolution of antibiotic resistance in bacteria? Using world-first microfluidic devices for single-cell evolution we are examining how readily these cells can develop resistance when exposed to antibiotics. Overall, our work has revealed DSB repair as a potential drug target and we are now exploring inhibitors as a strategy to re-sensitise antibiotic-resistant bacteria.