Mechanisms of antibiotic resistance in bacteria mediated by silver nanoparticles

ABSTRACTSilver nanoparticles (AgNPs) are widely used in industry, consumer products, and medical appliances due to their efficient antimicrobial properties. However, information on environmental toxicity and bacterial impact of these particles is not completely elucidated. Results showed that AgNPs produced growth inhibition and oxidative stress in bacteria Escherichia coli (gram negative) and Staphylococcus aureus (gram positive), with half-maximal inhibitory concentrations (IC50) of 12 and 7 mg/L, respectively. Surprisingly, bacteria pre-exposed to sublethal dose of AgNPs exhibited increased resistance toward antibiotics (ampicillin and Pen-Strep) with IC50 elevated by 3–13-fold. Further, AgNP pre-exposure raised the minimal inhibitory concentration and minimal biocidal concentration by two- to eightfold when cells were challenged with antibiotics with diverse mechanisms of action (penicillin, chloramphenicol, and kanamycin). Interestingly, we found that upon exposure to ampicillin, strains pretreated w...