title: Beta-lactam resistance in Staphylococcus aureus cells that do not require a cell wall for integrity.
abstract: Staphylococcus aureus ATCC 9144 cells with defective cell walls were generated on a medium with elevated osmolality in the presence of sublethal levels of penicillin G. On removal of antibiotic pressure, the cells exhibited stable penicillin and methicillin resistance. The resistance was homogeneous and its acquisition was enhanced following transient cell wall-defective growth. The resistant cells were mecA negative, beta-lactamase negative and did not contain any mutations in the coding regions of pbp genes. When penicillin was added back to resistant cells, they continued to grow and produced a diffuse cell wall that was resistant to the action by lysostaphin but was very sensitive to lysis with Triton X-100. These data indicate that the resistant cells are not dependent upon an intact cell wall for osmotic stability and they are able to switch readily to this mode of growth in the presence of penicillin G.
authors.affiliation: University Hospital of North Durham, United Kingdom.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Fuller
authors.forename: Catherine
authors.initials: C
authors.lastname: Elmer
authors.forename: Fiona
authors.initials: F
authors.lastname: Nattress
authors.forename: Richard
authors.initials: R
authors.lastname: Ellis
authors.forename: Glenda
authors.initials: G
authors.lastname: Horne
authors.forename: Peter
authors.initials: P
authors.lastname: Cook
authors.forename: Tony
authors.initials: T
authors.lastname: Fawcett
mesh_terms: D001426:Bacterial Proteins; D002473:Cell Wall / Q000378:metabolism / Q000502:physiology*; D010403:Penicillin Resistance / Q000502:physiology*; D046915:Penicillin-Binding Proteins; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; D047090:beta-Lactams; C487789:mecA protein, Staphylococcus aureus