title: Cell wall composition and decreased autolytic activity and lysostaphin susceptibility of glycopeptide-intermediate Staphylococcus aureus.
abstract: The cell wall composition and autolytic properties of passage-selected glycopeptide-intermediate Staphylococcus aureus (GISA) isolates and their parent strains were studied in order to investigate the mechanism of decreased vancomycin susceptibility. GISA had relatively modest changes in peptidoglycan composition involving peptidoglycan interpeptide bridges and somewhat decreased cross-linking compared to that of parent strains. The cell wall phosphorus content of GISA strains was lower than that of susceptible parent strains, indicating somewhat lower wall teichoic acid levels in the GISA strains. Similar to whole cells, isolated crude cell walls retaining autolytic activity of GISA had drastically reduced autolytic activity compared to that of parent strains, and this arose early in the development of the GISA phenotype. This was due to an alteration in the autolytic enzymes of GISA as revealed by normal susceptibility of GISA-purified cell walls to parental strain autolysin extract and lower activity and altered peptidoglycan hydrolase activity profiles in GISA autolysin extracts compared to those of parent strains. Northern blot analysis indicated that expression of atl, the major autolysin gene, was significantly downregulated in a GISA strain compared to that of its parent strain. In contrast to whole cells, which showed decreased lysostaphin susceptibility, purified cell walls of GISA showed increased susceptibility to lysostaphin. We suggest that in our GISA strains, decreased autolytic activity is involved in the tolerance of vancomycin and the activities of endogenous autolysins are important in conferring sensitivity to lysostaphin on whole cells.
authors.affiliation: Microbiology Group, Department of Biological Sciences, Illinois State University, Normal, IL 61790-4120, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Koehl
authors.forename: Arunachalam
authors.initials: A
authors.lastname: Muthaiyan
authors.forename: Radheshyam K
authors.initials: RK
authors.lastname: Jayaswal
authors.forename: Kerstin
authors.initials: K
authors.lastname: Ehlert
authors.forename: Harald
authors.initials: H
authors.lastname: Labischinski
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Wilkinson
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001433:Bacteriolysis / Q000187:drug effects*; D015152:Blotting, Northern; D002473:Cell Wall / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D006020:Glycopeptides / Q000494:pharmacology*; D008248:Lysostaphin / Q000494:pharmacology*; D010457:Peptidoglycan / Q000494:pharmacology; D010758:Phosphorus / Q000737:chemistry; D013211:Staphylococcus aureus / Q000187:drug effects*; D013682:Teichoic Acids / Q000378:metabolism; D020713:Vancomycin Resistance
chemical_list: D000900:Anti-Bacterial Agents; D006020:Glycopeptides; D010457:Peptidoglycan; D013682:Teichoic Acids; D010758:Phosphorus; D008248:Lysostaphin