Eight-year (2002-2009) Summary of the Linezolid (Zyvox® Annual Appraisal of Potency and Spectrum; ZAAPS) Program in European Countries

The linezolid surveillance network (ZAAPS Program) has been monitoring linezolid activity and susceptibility rates for eight years (2002-2009) in European medical centers. Samples from 12-24 sites annually in 11 countries were monitored by a central laboratory design using reference MIC methods with international and regional interpretations (EUCAST). A total of 13,404 Gram-positive pathogens were tested from 6 pathogen groups. Linezolid remained without documented resistance from 2002 through 2005, but beginning in 2006 resistant strains emerged at very low rates among Staphylococcus aureus (G2576T mutant in Ireland, 2007), coagulase-negative staphylococci (CoNS; usually Staphylococcus epidermidis, France and Italy in 2006-2009) and enterococci (Enterococcus faecium in Germany [2006, 2008, 20091 and E. faecalis in Sweden [2008], United Kingdom [2008] and Germany 120091); all but one strain having a target mutation. A mobile cfr was detected in an Italian CoNS strain (2008 and 2009), and clonal spread was noted for linezolid-resistant strains (PFGE results). Overall the linezolid susceptibility rates were >99.9, 99.7 and 99.6% for S. aureus, CoNS and enterococci, respectively; and all streptococcal strains were susceptible (MIC90, 1 mg/L). In conclusion, the ZAAPS Program surveillance confirmed high, sustained levels of linezolid activity from 2002-2009 and without evidence of MIC creep or escalating resistance. in Gram-positive pathogens across monitored European nations.