Vancomycin susceptibility in methicillin-resistant Staphylococcus aureus is mediated by YycHI activation of the WalRK essential two-component regulatory system.
The treatment of infections caused by methicillin-resistant Staphylococcus aureus is complicated by the emergence of strains with intermediate-level resistance to vancomycin (termed VISA). We have characterised a molecular pathway involved in the in vivo evolution of VISA mediated by the regulatory proteins YycH and YycI. In contrast to their function in other bacterial species, we report a positive role for these auxiliary proteins in regulation of the two-component regulator WalRK. Transcriptional profiling of yycH and yycI deletion mutants revealed downregulation of the 'WalRK regulon' including cell wall hydrolase genes atlA and sle1, with functional autolysis assays supporting these data by showing an impaired autolytic phenotype for each deletion strain. Using bacterial-two hybrid assays, we showed that YycH and YycI interact, and that YycHI also interacts with the sensor kinase WalK, forming a ternary protein complex. Mutation to YycH or YycI associated with clinical VISA strains had a deleterious impact on the YycHI/WalK complex, suggesting that the interaction is important for the regulation of WalRK. Taken together, we have described a novel antibiotic resistance strategy for the human pathogen S. aureus, whereby YycHI mutations are selected for in vivo leading to reduced WalRK activation, impaired cell wall turnover and ultimately reduced vancomycin efficacy.
Department of Microbiology, Monash University, Melbourne, Australia.
David R
DR
Cameron
Department of Microbiology, Monash University, Melbourne, Australia.
Jhih-Hang
JH
Jiang
Department of Microbiology, Monash University, Melbourne, Australia.
Xenia
X
Kostoulias
Department of Microbiology, Monash University, Melbourne, Australia.
Daniel J
DJ
Foxwell
Department of Microbiology, Monash University, Melbourne, Australia.|Department of Infectious Diseases, Alfred Hospital and Monash University, Melbourne, Australia.
Anton Y
AY
Peleg
D001426:Bacterial Proteins / Q000235:genetics*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009876:Operon; D014640:Vancomycin / Q000494:pharmacology; D020713:Vancomycin Resistance
D001426:Bacterial Proteins; D014640:Vancomycin