title: An electron microscopic study of clinical and laboratory-derived strains of teicoplanin-resistant Staphylococcus haemolyticus.
abstract: Staphylococcal resistance to glycopeptides (which involves more teicoplanin than vancomycin) is uncommon and largely confined to Staphylococcus haemolyticus, an emerging nosocomial pathogen with a tendency to develop antibiotic resistance. In this study, six S. haemolyticus strains, including two isogenic pairs of teicoplanin-susceptible/-resistant strains and two resistant clinical isolates, were used in a morphologic and morphometric electron microscope investigation. Cells from both clinical and laboratory-derived teicoplanin-resistant strains exhibited abnormally roughened, irregular outlines when observed by transmission electron microscopy. However, no significant differences in cell wall thickness resulted from morphometric analysis when the susceptible/resistant cells of the two isogenic pairs were compared. By scanning electron microscopy, an abnormally roughened, blistered surface was associated with teicoplanin-resistant cocci. A certain variability was noted between strains, not clearly related to the resistance level. In freeze-fracture investigations, a higher number per square micrometer of intramembrane particles, more significant in the E than in the P membrane fracture face, was observed in the laboratory-derived resistant clones as compared to susceptible parent strains. Further studies are needed to understand the cause-effect relation between these ultrastructural alterations and staphylococcal resistance to teicoplanin (but not to vancomycin).
authors.affiliation: Institute of Microbiology, University of Ancona Medical School, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Giovanetti
authors.forename: F
authors.initials: F
authors.lastname: Biavasco
authors.forename: A
authors.initials: A
authors.lastname: Pugnaloni
authors.forename: R
authors.initials: R
authors.lastname: Lupidi
authors.forename: G
authors.initials: G
authors.lastname: Biagini
authors.forename: P E
authors.initials: PE
authors.lastname: Varaldo
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000648:ultrastructure; D002473:Cell Wall / Q000187:drug effects / Q000648:ultrastructure; D005614:Freeze Fracturing; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D013203:Staphylococcal Infections / Q000382:microbiology; D013210:Staphylococcus / Q000187:drug effects* / Q000648:ultrastructure*; D017334:Teicoplanin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D017334:Teicoplanin