Update on the In Vitro Activity of Daptomycin Tested against 17,193 Gram-positive Bacteria Isolated from European Medical Centers (2005-2007)

The antimicrobial susceptibility patterns of 17,193 Gram-positive isolates consecutively collected from 28 medical centers in 12 countries in Europe and Israel in 2005-2007 were evaluated by Clinical and Laboratory Standards Institute (CLSI) broth microdilution methods supplemented with calcium to 50 mg/L for testing daptomycin. Overall, the rate of methicillin-resistant Staphylococcus aureus (MRSA) was 28.3%, varying from 32.3% in 2005 to 27.1% in 2006 and 28.5% in 2007. Vancomycin resistance rates were 0.8% and 21.5% among Enterococcus faecalis and E. faecium, respectively. Among E. faecium, vancomycin resistance increased from 17.9% in 2005 to 26.3% in 2007, and varied from 0.0% in Spain, Sweden and Switzerland to as high as 54.6% in Ireland for 2007. All isolates tested, except for seven CONS (0.2%; 3,234 tested) were considered susceptible to daptomycin using breakpoints established by the United States Food and Drug Administration, the CLSI and the EUCAST. Daptomycin was very active against all Gram-positive species with the highest minimum inhibitory concentration (MIC) results being 1, 4, 2 and 4 mg/L for S. aureus, coagulase-negative staphylococci, E. faecalis and E. faecium, respectively. Daptomycin activity was not adversely influenced by resistance to oxacillin among staphylococci or to vancomycin among enterococci.