Parallel evolutionary pathways to antibiotic resistance selected by biocide exposure.

Area of Science:

• Microbiology
• Molecular Biology
• Public Health

Background:

• Biocides are extensively utilized for infection control.
• The potential for biocides to induce antibiotic resistance is a growing concern.

Purpose of the Study:

• To investigate if exposure to various biocides drives antibiotic resistance in Salmonella.
• To identify the mechanisms underlying biocide-induced antibiotic resistance.

Main Methods:

• Salmonella Typhimurium was exposed to four biocides with distinct mechanisms of action.
• Antibiotic-resistant mutants were selected and characterized phenotypically and genotypically.

Main Results:

• All tested biocides selected for multidrug-resistant (MDR) mutants with reduced antibiotic susceptibility.
• Mutations in the AcrAB-TolC efflux pump and a novel mutation in rpoA were identified as contributing to MDR.
• Some mutants exhibited cross-resistance to quinolone antibiotics and triclosan.

Conclusions:

• Biocide exposure can select for antibiotic-resistant bacterial mutants.
• The identified resistance mechanisms are clinically relevant and found in human pathogens.