Salicylate induction of phenotypic resistance to quinolones in Serratia marcescens

The influence of salicylic acid on the permeability and susceptibility of Serratia marcescens to both nalidixic acid and ciprofloxacin was studied, as well as the effect of salicylate on outer membrane proteins and lipopolysaccharide. As salicylic acid concentration increased, ciprofloxacin accumulation decreased with a concomitant, previously observed, reduction in the porin content of the outer membrane. Resistance to ciprofloxacin and nalidixic acid was enhanced when bacteria grew in the presence of salicylic acid.