In vitro activity of linezolid as assessed through the 2013 LEADER surveillance program

The 2013 LEADER surveillance program monitored the in vitro activity of linezolid and comparator agents against Gram-positive bacteria at 60 medical centers in the United States. A total of 7183 pathogens were contributed from 6 predetermined pathogen groups. The groups were Staphylococcus aureus, coagulase-negative staphylococci, enterococci, Streptococcus pneumoniae,beta-hemolytic streptococci, and viridans group streptococci. The MIC90 value for each of the 6 pathogen groups was 1 mu g/mL. Susceptibility of all organisms to linezolid was 99.83%. Only 12 isolates (2 S. aureus, 3 Staphylococcus epidermidis, 1 Streptococcus sanguinis, 5 Enterococcus faecium, and 1 Enterococcus faecalis) were nonsusceptible to linezolid (0.17%). Three of these (2 S. aureus and 1 E. faecium) harbored the cfr resistance mechanism. The findings indicate that linezolid activity remains stable, although there are examples of clonal dissemination within several monitored institutions. (C) 2015 Elsevier Inc. All rights reserved.