Abstract
Antibiotic resistance is a main threat to the public health. It is established that the overuse and misuse of antibiotics are highly contributing to antibiotic resistance. However, the impact of nonantibiotic antimicrobial agents like biocides on antibiotic resistance is currently investigated and studied. Triclosan (TCS) is a broad-spectrum antibacterial agent widely used as antiseptic and disinfectant. In this study, we aimed to evaluate the effect of exposure of Proteus mirabilis clinical isolates to sublethal concentrations of TCS on their antibiotic susceptibility, membrane characteristics, efflux activity, morphology, and lipid profile. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of TCS were determined for 31 P. mirabilis clinical isolates. The tested isolates were adapted to increasing sublethal concentrations of TCS. The MICs of 16 antibiotics were determined before and after adaptation. Membrane characteristics, efflux activity, ultrastructure, and lipid profile of the tested isolates were examined before and after adaptation. Most adapted P. mirabilis isolates showed increased antibiotic resistance, lower membrane integrity, lower outer and inner membrane permeability, and higher membrane depolarization. Nonsignificant change in membrane potential and lipid profile was found in adapted cells. Various morphological changes and enhanced efflux activity was noticed after adaptation. The findings of the current study suggest that the extensive usage of TCS at sublethal concentrations could contribute to the emergence of antibiotic resistance in P. mirabilis clinical isolates. TCS could induce changes in the bacterial membrane properties and increase the efflux activity and in turn decrease its susceptibility to antibiotics which would represent a public health risk.