title: Cell wall deficiency and its effect on methicillin heteroresistance in Staphylococcus aureus.
abstract: Clinical strains of Staphylococcus aureus with different phenotypic methicillin susceptibility characteristics, bearing or lacking the mecA gene, were tested for their ability to transform into a cell wall-deficient state under special conditions of cultivation. Conversion to L-form growth with formation of typical L-form 'fried egg' colonies and expression of oxacillin resistance was observed in sensitive (mecA-negative) and heteroresistant (mecA-positive) strains. Transmission electron microscopy observation of these strains revealed pleomorphic populations of cell wall-deficient cells with ultrastructure morphology similar to that of a control stable L-form strain of S. aureus. The results demonstrate that expression of phenotypic methicillin resistance could be associated with cell wall deficiency in S. aureus strains and could underlie the phenomenon of heteroresistance.
authors.affiliation: Institute of Microbiology, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria. nadya.markova@gmail.com
authors.forename: Nadya
authors.initials: N
authors.lastname: Markova
authors.forename: Irina
authors.initials: I
authors.lastname: Haydoushka
authors.forename: Lilia
authors.initials: L
authors.lastname: Michailova
authors.forename: Rumyana
authors.initials: R
authors.lastname: Ivanova
authors.forename: Violeta
authors.initials: V
authors.lastname: Valcheva
authors.forename: Mimi
authors.initials: M
authors.lastname: Jourdanova
authors.forename: Tatyana
authors.initials: T
authors.lastname: Popova
authors.forename: Tatyana
authors.initials: T
authors.lastname: Radoucheva
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002473:Cell Wall / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D016106:Methicillin Resistance; D046529:Microscopy, Electron, Transmission; D010068:Oxacillin / Q000494:pharmacology*; D046915:Penicillin-Binding Proteins; D011523:Protoplasts / Q000187:drug effects*; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; C487789:mecA protein, Staphylococcus aureus; D010068:Oxacillin