Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2022

Defects in DNA double-strand break repair re-sensitise antibiotic-resistant Escherichia coli to multiple bactericidal antibiotics (82628)

Sarah Revitt-Mills 1 2 , Elizabeth K Wright 1 2 , Madaline Vereker 1 2 , Callum O'Flaherty 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. There is an urgent need to develop new types of antibiotics with novel modes of action. One promising strategy is to develop resistance-breaker compounds, which inhibit resistance mechanisms and thus re-sensitise bacteria to existing antibiotics. This work has identified bacterial DNA double-strand break repair (DSB) as a promising target for the development of such resistance-breaking co-therapies 

We have found that inactivation of DSB repair (via recA and recB mutations) significantly enhanced the killing of both ciprofloxacin-sensitive (CipS) and ciprofloxacin-resistant (CipR) Escherichia coli following antibiotic treatment (minimum inhibitory concentrations (MICs) [mg/ml] CipSbackground: rec+ 0.014 ± 0.005; ΔrecA 0.0006 ± 0.001; ΔrecB 0.001 ± 0.001. MICs [mg/ml] CipRbackground: rec+ 9.2 ± 2.7; ΔrecA 1.5 ± 0.9; ΔrecB 1.6 ± 0.9). Disrupting DSB repair also produced potentiating effects with other bactericidal antibiotics. For kanamycin and trimethoprim, sensitivity manifested through increased rates of killing at high antibiotic concentrations. For ampicillin, repair defects dramatically reduced antibiotic tolerance. Further, induction of the pro-mutagenic SOS response was reduced, or eliminated, in cells exposed to ciprofloxacin, nitrofurantoin or trimethoprim (SOS undetectable in ampicillin or kanamycin-treated cells).   

This work has identified 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? By developing world-first microfluidic devices for single-cell evolution we are beginning to observe how readily these cells can develop resistance when exposed to antibiotics. Overall, our findings suggest that if break-repair inhibitors can be developed they could re-sensitise antibiotic-resistant bacteria to multiple classes of existing antibiotics and may supress the development of de novo antibiotic-resistance mutations.