title: Increased cell wall teichoic acid production and D-alanylation are common phenotypes among daptomycin-resistant methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates.
abstract: Multiple mechanisms have been correlated with daptomycin-resistance (DAP-R) in Staphylococcus aureus. However, one common phenotype observed in many DAP-R S. Aureus strains is a thickened cell wall (CW). The first evidence for an impact of CW-linked glycopolymers on this phenotype was recently demonstrated in a single, well-characterized DAP-R methicillin-susceptible S. aureus (MSSA) strain. In this isolate the thickened CW phenotype was linked to an increased production and D-alanylation of wall teichoic acids (WTA). In the current report, we extended these observations to methicillin-resistant daptomycin-sensitive/daptomyin-resistant (DAP-S/DAP-R) strain-pairs. These pairs included methicillin-resistant S. aureus (MRSA) isolates with and without single nucleotide polymorphisms (SNPs) in mprF (a genetic locus linked to DAP-R phenotype). We found increased CW dry mass in all DAP-R vs DAP-S isolates. This correlated with an increased expression of the WTA biosynthesis gene tagA, as well as an increased amount of WTA in the DAP-R vs DAP-S isolates. In addition, all DAP-R isolates showed a higher proportion of WTA D-alanylation vs their corresponding DAP-S isolate. We also detected an increased positive surface charge amongst the DAP-R strains (presumably related to the enhanced D-alanylation). In comparing the detailed CW composition of all isolate pairs, substantive differences were only detected in one DAP-S/DAP-R pair. The thickened CW phenotype, together with an increased surface charge most likely contributes to either: i) a charge-dependent repulsion of calcium complexed-DAP; and/or ii) steric-limited access of DAP to the bacterial cell envelope target. Taken together well-defined perturbations of CW structural and functional metrics contribute to the DAP-R phenotype and are common phenotypes in DAP-R S. Aureus isolates, both MSSA and MRSA. Note: Although "daptomycin-nonsusceptibility" is the generally accepted terminology, we have utilized the term "daptomycin resistance" for ease of presentation in this manuscript.
authors.affiliation: Interfakultäres Institut für Mikrobiologie und Infektionsmedizin, Microbial Genetics, University of Tübingen, Tübingen, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Bertsche
authors.forename: Soo-Jin
authors.initials: SJ
authors.lastname: Yang
authors.forename: Daniel
authors.initials: D
authors.lastname: Kuehner
authors.forename: Stefanie
authors.initials: S
authors.lastname: Wanner
authors.forename: Nagendra N
authors.initials: NN
authors.lastname: Mishra
authors.forename: Tobias
authors.initials: T
authors.lastname: Roth
authors.forename: Mulugeta
authors.initials: M
authors.lastname: Nega
authors.forename: Alexander
authors.initials: A
authors.lastname: Schneider
authors.forename: Christoph
authors.initials: C
authors.lastname: Mayer
authors.forename: Timo
authors.initials: T
authors.lastname: Grau
authors.forename: Arnold S
authors.initials: AS
authors.lastname: Bayer
authors.forename: Christopher
authors.initials: C
authors.lastname: Weidenmaier
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism*; D017576:Daptomycin / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D010457:Peptidoglycan / Q000737:chemistry / Q000378:metabolism; D010641:Phenotype; D013203:Staphylococcal Infections / Q000382:microbiology; D013682:Teichoic Acids / Q000096:biosynthesis*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D010457:Peptidoglycan; D013682:Teichoic Acids; D017576:Daptomycin