Evolution of Multidrug Resistance during Staphylococcus aureus Infection Involves Mutation of the Essential Two Component Regulator WalKR
(A) and (B) Vancomycin population analysis results demonstrate increased resistance in strains containing walK or walR mutations. (C) and (D) Autolytic activity for clinical and mutant strains demonstrates reduced autolytic activity in strains containing walK or walR mutations. All results are expressed as mean ± SEM for at least 3 biological replicates. (E) Biofilm analysis of clinical and mutant strains using a 96-well plate biofilm assay. The presence of walK or walR mutations significantly reduces biofilm formation compared to parental strains, mimicking the impact of the VISA phenotype on biofilm formation. All results are expressed as mean ± SEM for at least 3 biological replicates. Statistical analysis was performed comparing VISA and mutant strains to the parental strains JKD6009 or JKD6004 (** p<0.01; *** p<0.001). (F) Analysis of agr activity of clinical and mutant strains by real time quantitative PCR of the effector molecule RNAIII. Results are presented relative to the parental strain JKD6009 or JKD6004 which has been normalized to 1. All results are expressed as mean ± SEM for at least 3 biological replicates.