Triclosan resistance in methicillin-resistant Staphylococcus aureus (MRSA)

Two triclosan selected mutants showed four-fold and 16-fold increases in their minimum inhibitory concentrations (MICs) of triclosan (1 mg/L and 4 mg/L) compared with their parent strains. Four clinical isolates of MRSA were detected with the same triclosan susceptibility as the mutants. One mutant had a predicted change in the gene product on FabI (Thr 147-->His), whilst only one clinical isolate had predicted FabI amino-acid changes (Ala 198-->Gly, and Leu 208-->Phe). The lack of fabI mutations in one mutant and three of the clinical isolates showing reduced triclosan susceptibility suggest that genetic loci other than fabI may be involved in triclosan resistance.