Aims
To identify factors associated with the Staphylococcus aureus pine-oil disinfectant-reduced-susceptibility (PD(RS)) mechanism and to describe one possible PD(RS) model.
Conclusions
The PD(RS) mechanism proposed results from increased catabolic capabilities and increased flux through the mevalonate pathway as well as altered bactoprenol physiology. Significance and impact of the study: A novel mechanism that bacteria utilize to overcome the killing effects of PD formulations is proposed that is unique from the PD(RS) mechanism of the enterobacteraciae.
Results
Comparative genomic sequencing (CGS) and microarray analysis were utilized to detect mutations and transcriptome alterations that occur in a S. aureus PD(RS) 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 PD(RS) mutant. CGS uncovered three mutations in a PD(RS) 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. PD(RS) mutants demonstrated reduced susceptibility to bacitracin and farnesol, and one PD(RS) mutant displayed upregulation of bacA, a bacitracin-resistance gene. Collectively, this evidence demonstrates altered undecaprenol metabolism in PD(RS) mutants. Conclusions: The PD(RS) mechanism proposed results from increased catabolic capabilities and increased flux through the mevalonate pathway as well as altered bactoprenol physiology. Significance and impact of the study: A novel mechanism that bacteria utilize to overcome the killing effects of PD formulations is proposed that is unique from the PD(RS) mechanism of the enterobacteraciae.