title: Multicenter assessment of the linezolid spectrum and activity using the disk diffusion and Etest methods: report of the Zyvox(R) antimicrobial potency study in Latin America (LA-ZAPS).
abstract: Linezolid was the first clinically applied member of the new antimicrobial class called the oxazolidinones. These agents have a powerful spectrum of activity focussed against Gram-positive organisms including strains with documented resistances to other antimicrobial classes. We conducted a multicenter surveillance (Zyvox Antimicrobial Potency Study; ZAPS) trial of qualifying Gram-positive isolates from 24 medical centers in eight countries in Latin America. The activity and spectrum of linezolid was compared to numerous agents including glycopeptides, quinupristin/dalfopristin, beta-lactams and fluoroquinolones when testing 2,640 strains by the standardized disk diffusion method or Etest (AB BIODISK, Solna, Sweden). The linezolid spectrum was complete against staphylococci (median zone diameter, 29 - 32 mm), as was the spectrum of vancomycin and quinupristin/dalfopristin. Among the enterococci, no linezolid resistance was detected, and the susceptibility rate was 93.1 - 96.4%. Only the vancomycin-susceptible Enterococcus faecium strains remained susceptible (92.8%) to quinupristin/dalfopristin. Marked differences in the glycopeptide resistance patterns (van A versus van B) were noted for the 22 isolates of VRE, thus requiring local susceptibility testing to direct therapy. Streptococcus pneumoniae and other species were very susceptible (100.0%) to linezolid, MIC(90) at 0.75 microg/ml. Penicillin non-susceptible rate was 27.7% and erythromycin resistance was at 17.4%. Other streptococci were also completely susceptible to linezolid (MIC(90), 1 microg/ml). These results provide the initial benchmark of potency and spectrum for linezolid in Latin American medical centers. Future comparisons should recognize that the oxazolidinones possess essentially a complete spectrum coverage of the monitored staphylococci, enterococci and streptococcal isolates in 2000-2001. This positions linezolid as the widest spectrum empiric choice against multi-resistant Gram-positive cocci, a spectrum of activity greater than available glycopeptides and the streptogramin combination.
authors.affiliation: The Buffalo Clinical Research Center, Buffalo, NY, USA.
authors.forename: Charles H
authors.initials: CH
authors.lastname: Ballow
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Biedenbach
authors.forename: Flavia
authors.initials: F
authors.lastname: Rossi
authors.forename: Ronald N
authors.initials: RN
authors.lastname: Jones
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004058:Diffusion; D024881:Drug Resistance, Bacterial; D006094:Gram-Positive Bacteria / Q000187:drug effects*; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology; D006801:Humans; D007843:Latin America; D000069349:Linezolid; D008826:Microbial Sensitivity Tests / Q000379:methods*; D023303:Oxazolidinones / Q000494:pharmacology*; D013045:Species Specificity; D020713:Vancomycin Resistance
chemical_list: D000081:Acetamides; D000900:Anti-Bacterial Agents; D023303:Oxazolidinones; D000069349:Linezolid