Genetic changes that correlate with the pine-oil disinfectant-reduced susceptibility mechanism of Staphylococcus aureus

摘要

To identify factors associated with the Staphylococcus aureus pine-oil disinfectant-reduced-susceptibility (PDRS) mechanism and to describe one possible PDRS model. Comparative genomic sequencing (CGS) and microarray analysis were utilized to detect mutations and transcriptome alterations that occur in a S. aureus PDRS mutant. Mutant analysis, antimicrobial gradient plates, growth studies and 3-hydroxy-3-methylglutaryl coenzyme A synthase assays were then performed to confirm the biological consequences of the 'omics' alterations detected in a PDRS mutant. CGS uncovered three mutations in a PDRS mutant in a(n): alcohol dehydrogenase (adh), catabolite control protein A (ccpA) and an NADPH-flavin oxidoreductase (frp). These mutations lead to increased growth rates; increased transcription of an NAD-dependent d-lactate dehydrogenase gene (ddh); and increased flux through the mevalonate pathway. PDRS mutants demonstrated reduced susceptibility to bacitracin and farnesol, and one PDRS mutant displayed upregulation of bacA, a bacitracin-resistance gene. Collectively, this evidence demonstrates altered undecaprenol metabolism in PDRS mutants. The PDRS mechanism proposed results from increased catabolic capabilities and increased flux through the mevalonate pathway as well as altered bactoprenol physiology. A novel mechanism that bacteria utilize to overcome the killing effects of PD formulations is proposed that is unique from the PDRS mechanism of the enterobacteraciae.