title: Emergence of methicillin-resistant Staphylococcus aureus with intermediate glycopeptide resistance: clinical significance and treatment options.
abstract: Methicillin-resistant Staphylococcus aureus is a pathogen that is associated with serious infections that pose a significant risk of morbidity and mortality because of their multidrug resistant nature. Until recently, therapeutic options were limited to vancomycin, making the use of this drug widespread. Unfortunately, the continued application of this drug has led to the emergence of glycopeptide intermediate susceptible S. aureus (GISA). By definition, these organisms demonstrated a vancomycin minimum inhibitory concentration (MIC) of >4 mg/L and <32 mg/L. However, although the mechanism of resistance is not fully elucidated at this time, GISA strains have demonstrated thickened or aggregated cell walls, an increase in penicillin binding proteins and greater autolytic activity. At present, the overall number of reported cases of GISA is relatively low. In most cases, thus far, prolonged courses of vancomycin were reported. A few cases reported monitoring serum vancomycin concentrations but because of limited information, no association with outcome can be made. Whether these GISA strains will become more widespread or evolve into fully glycopeptide resistant strains is unknown at this time. Although there are a number of new agents that possess activity against these pathogens, there is no consensus regarding specific recommendations for treatment. Strict infection control practices, routine screening for resistance and controlled use of antibacterial agents, especially vancomycin, are critical steps in preventing the further development of resistance among staphylococci.
authors.affiliation: Wayne State University, Department of Pharmacy Services, Detroit Receiving Hospital and University Health Center, Michigan 48201, USA. m.j.rybak@wayne.edu
authors.forename: M J
authors.initials: MJ
authors.lastname: Rybak
authors.forename: R L
authors.initials: RL
authors.lastname: Akins
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D006801:Humans; D016106:Methicillin Resistance / Q000502:physiology*; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000502:physiology; D014640:Vancomycin / Q000627:therapeutic use*
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin