Effect of recA inactivation on mutagenesis of Escherichia coli exposed to sublethal concentrations of antimicrobials

concentrations of some antibiotics have been reported to stimulate mutagenesis and recom-bination, which may facilitate bacterial adaptation to different types of stress, including antibiotic pressure. However, the mutagenic effect of most of the currently used antibiotics remains untested. Furthermore, it is known that in many bacteria, including Escherichia coli, stimulation of mutagenesis is mediated by the SOS response. Thus, blockage or attenuation of this response through the inhibition of RecA has been proposed as a possible therapeutic adjuvant in combined therapy to reduce the ability to generate antibiotic-resistant mutants. The aim of this work was to study the capacity of sublethal concentrations of antimicrobials of differ-ent families with different molecular targets to increase the mutant frequency of E. coli, and the effect that inactivation of recA would have on antibiotic-mediated mutagenesis. Methods: We tested the mutagenicity of the following antimicrobials: ampicillin; ceftazidime; imipenem; fosfo