Combined inactivation of the SOS response with TCA fumarases and the adaptive response enhances antibiotic susceptibility against .

INTRODUCTION

Targeting bacterial DNA damage responses such as the SOS response represents a promising strategy for enhancing the efficacy of existing antimicrobials. This study focuses on a recently discovered DNA damage response mechanism involving tricarboxylic acid cycle (TCA) fumarases and the adaptive response, crucial for survival in the presence of genotoxic methyl methanesulfonate (MMS). We investigated whether this pathway contributes to protection against antibiotics, either separately or in combination with the SOS response.

METHODS

An isogenic collection of BW25113 mutants was used, including strains deficient in fumarases (Δ, Δ, Δ) and the adaptive response (Δ, Δ Δ). Additional SOS response inactivation (Δ) was conducted by P1 phage transduction. All mutants were subjected to antimicrobial susceptibility testing, growth curve analysis, survival and evolution assays. To validate the relevance of these findings, experiments were also performed in a quinolone-resistant ST131 clinical isolate.

RESULTS AND DISCUSSION

Overall, no significant differences or only moderate increases in susceptibility were observed in the single mutants, with Δ and Δ mutants showing the highest susceptibility. To enhance this effect, these genes were then inactivated in combination with the SOS response by constructing Δ/Δ and Δ/Δ mutants. These combinations exhibited significant differences in susceptibility to various antimicrobials, particularly cephalosporins and quinolones, and especially in the Δ/Δ strain. To further assess these results, we constructed an ST131 Δ/Δ mutant, in which a similar trend was observed. Together, these findings suggest that co-targeting the SOS response together with fumarases or the adaptive response could enhance the effectiveness of antibiotics against , potentially leading to new therapeutic strategies.