RecA Inhibitors Potentiate Antibiotic Activity and Block Evolution of Antibiotic Resistance

Abstract

Antibiotic resistance arises from the maintenance of resistance mutations or genes acquired from the acquisition of adaptive de novo mutations or the transfer of resistance genes. Antibiotic resistance is acquired in response to antibiotic therapy by activating SOS-mediated DNA repair and mutagenesis and horizontal gene transfer pathways. Initiation of the SOS pathway promotes activation of RecA, inactivation of LexA repressor, and induction of SOS genes. Here, we have identified and characterized phthalocyanine tetrasulfonic acid RecA inhibitors that block antibiotic-induced activation of the SOS response. These inhibitors potentiate the activity of bactericidal antibiotics, including members of the quinolone, β-lactam, and aminoglycoside families in both Gram-negative and Gram-positive bacteria. They reduce the ability of bacteria to acquire antibiotic resistance mutations and to transfer mobile genetic elements conferring resistance. This study highlights the advantage of including RecA inhibitors in bactericidal antibiotic therapies and provides a new strategy for prolonging antibiotic shelf life.

Antibiotic efficacy — context matters

“…These findings have been supported genetically, as deletion of SOS response genes enhances drug susceptibility [11,16], while over-expression of mismatch repair genes confers protection [16,33]. Moreover, biochemical inhibition of RecA with polysulfonated compounds potentiates the lethality of multiple antibiotics against both Gram-negative and Gram-positive bacteria [61,62]. Oxidative damage to the nucleotide pool may, in part, underlie this phenotype [29], as incorporation of 8-oxo-guanine induces mismatch repair defects that trigger the formation of double-stranded DNA breaks [16].…”

The Challenge of Overcoming Antibiotic Resistance: An Adjuvant Approach?

“…Examples include inhibition of BlaR1 and MecR1 mediated detection of β -lactam antibiotics in S. aureus , 27 interference with the SOS DNA repair and mutagenesis pathway, 28 and interference with one of the many two-component signaling system (TCS) pathways that play a role in antibiotic resistance. 29 …”

Exploiting epistasis to perturb the evolution of antibiotic resistance

“…1B-D, Methods). Keeping the cultures in exponential phase with vigorous shaking while continually adjusting the antibiotic concentration maintains a strong selection 15 pressure, specifically for faster growth in the presence of the antibiotic and thus higher resistance (as measured by the IC50). In this way, fair comparisons of resistance evolution between hundreds of bacterial populations of the same size that undergo the same number of generations and experience the same clearly defined selection pressure become possible.…”

“…10 The ability of different genotypes to spontaneously evolve drug resistance (here: "resistance evolvability") can be determined by exposing them to equivalent selection pressures in evolution experiments and comparing the evolutionary outcomes (17). For a meaningful quantitative comparison, it is essential to control both the number of generations and the population size of the evolving genotypes (18,19) -a characteristic which is achievable due to recent technological 15 advances (20,21). The outcome of such evolution experiments then depends on the key evolutionary determinants of the starting genotype, including its mutation rate and the distribution of fitness effects of resistance mutations.…”