title: Ultrastructural cell wall characteristics of clinical gentamycin-resistant Staphylococcus aureus isolates.
abstract: The frequent use of gentamycin (GM) ointment for the treatment of skin infections has led to an increase in the number of GM-resistant clinical isolates of Staphylococcus aureus. We examined the ultrastructural characteristics of 14 clinical strains of S. aureus by transmission electron microscopy. Seven of these isolates were GM-resistant, and seven isolates were GM-sensitive. We found that the cell wall of GM-resistant strains (32.24 ± 5.99 nm) was significantly thicker than that of GM-sensitive strains (19.02 ± 2.72 nm). We genetically characterized these isolates by polymerase chain reaction, targeting the genes for three aminoglycoside-modifying enzymes, aac(6')-aph(2''), aph(3')-III, and ant(4')-I. All GM-resistant strains tested carried the gene encoding aac(6')-aph(2''). However, we were unable to establish a link between a specific gene and cell wall thickening, because one GM-resistant strain was also positive for aph(3')-III. We also demonstrated that a GM-resistant mutant strain, derived in vitro from a GM-sensitive S. aureus parent strain (209P), also exhibited a thickened cell wall. These results strongly suggest that a thickened cell wall is a common ultrastructural characteristic of GM-resistant S. aureus clinical strains.
authors: Department of Otolaryngology, Kawasaki Medical School, 577 Matsusima, Kurasiki, Okayama, Japan. fuku29fukusuke@yahoo.co.jp
authors: Kenji
authors: K
authors: Fukutsuji
authors: Sakuo
authors: S
authors: Yamada
authors: Tamotsu
authors: T
authors: Harada
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D002473:Cell Wall / Q000187:drug effects / Q000648:ultrastructure*; D005839:Gentamicins / Q000627:therapeutic use*; D006801:Humans; D016106:Methicillin Resistance / Q000187:drug effects / Q000235:genetics; D008826:Microbial Sensitivity Tests; D046529:Microscopy, Electron, Transmission; D013207:Staphylococcal Skin Infections / Q000235:genetics / Q000382:microbiology; D013211:Staphylococcus aureus / Q000235:genetics / Q000472:pathogenicity / Q000648:ultrastructure*
chemical_list: D000900:Anti-Bacterial Agents; D005839:Gentamicins