title: Transcriptomic and functional analysis of an autolysis-deficient, teicoplanin-resistant derivative of methicillin-resistant Staphylococcus aureus.
abstract: The molecular basis of glycopeptide-intermediate S. aureus (GISA) isolates is not well defined though frequently involves phenotypes such as thickened cell walls and decreased autolysis. We have exploited an isogenic pair of teicoplanin-susceptible (strain MRGR3) and teicoplanin-resistant (strain 14-4) methicillin-resistant S. aureus strains for detailed transcriptomic profiling and analysis of altered autolytic properties. Strain 14-4 displayed markedly deficient Triton X-100-triggered autolysis compared to its teicoplanin-susceptible parent, although microarray analysis paradoxically did not reveal significant reductions in expression levels of major autolytic genes atl, lytM, and lytN, except for sle1, which showed a slight decrease. The most important paradox was a more-than-twofold increase in expression of the cidABC operon in 14-4 compared to MRGR3, which was correlated with decreased expression of autolysis negative regulators lytSR and lrgAB. In contrast, the autolysis-deficient phenotype of 14-4 was correlated with both increased expression of negative autolysis regulators (arlRS, mgrA, and sarA) and decreased expression of positive regulators (agr RNAII and RNAIII). Quantitative bacteriolytic assays and zymographic analysis of concentrated culture supernatants showed a striking reduction in Atl-derived, extracellular bacteriolytic hydrolase activities in 14-4 compared to MRGR3. This observed difference was independent of the source of cell wall substrate (MRGR3 or 14-4) used for analysis. Collectively, our results suggest that altered autolytic properties in 14-4 are apparently not driven by significant changes in the transcription of key autolytic effectors. Instead, our analysis points to alternate regulatory mechanisms that impact autolysis effectors which may include changes in posttranscriptional processing or export.
authors.affiliation: Service of Infectious Diseases, University Hospitals of Geneva, CH-1211 Geneva 14, Switzerland.
authors.forename: Adriana
authors.initials: A
authors.lastname: Renzoni
authors.forename: Christine
authors.initials: C
authors.lastname: Barras
authors.forename: Patrice
authors.initials: P
authors.lastname: François
authors.forename: Yvan
authors.initials: Y
authors.lastname: Charbonnier
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Huggler
authors.forename: Christian
authors.initials: C
authors.lastname: Garzoni
authors.forename: William L
authors.initials: WL
authors.lastname: Kelley
authors.forename: Paul
authors.initials: P
authors.lastname: Majcherczyk
authors.forename: Jacques
authors.initials: J
authors.lastname: Schrenzel
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Lew
authors.forename: Pierre
authors.initials: P
authors.lastname: Vaudaux
mesh_terms: D001433:Bacteriolysis / Q000235:genetics; D002473:Cell Wall / Q000235:genetics; D045604:Extracellular Fluid / Q000201:enzymology; D006801:Humans; D006867:Hydrolases / Q000378:metabolism; D016106:Methicillin Resistance; D017830:Octoxynol; D020411:Oligonucleotide Array Sequence Analysis; D010447:Peptide Hydrolases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D013211:Staphylococcus aureus / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D017334:Teicoplanin / Q000494:pharmacology*; D014158:Transcription, Genetic
chemical_list: D017334:Teicoplanin; D017830:Octoxynol; D006867:Hydrolases; D010447:Peptide Hydrolases