Multicenter assessment of the linezolid spectrum and activity using the disk diffusion and Etest methods: report of the Zyvox® Antimicrobial Potency Study in Latin America (LA-ZAPS)

• Main Author: Ballow,Charles H.
• Publication Date: 2002
• Other Authors: Biedenbach,Douglas J., Rossi,Flavia, Jones,Ronald N.
• Format: Article
• Language: eng
• Source: Brazilian Journal of Infectious Diseases
• Download full: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S1413-86702002000300001
• topic: Linezolid; oxazolidinones; antimicrobial surveillance; resistant Gram-positive cocci; ZAPS

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, b-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, MIC90 at 0.75 mug/ml. Penicillin non-susceptible rate was 27.7% and erythromycin resistance was at 17.4%. Other streptococci were also completely susceptible to linezolid (MIC90, 1 mug/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.