Baseline study to determine in vitro activities of daptomycin against gram-positive pathogens isolated in the United States in 2000-2001.
The activity of daptomycin was assessed by using 6,973 gram-positive bacteria isolated at 50 United States hospitals in 2000 and 2001. Among the isolates of Streptococcus pneumoniae (n = 1,163) collected, the rate of penicillin resistance was 16.1%; rates of oxacillin resistance among Staphylococcus aureus isolates (n = 1,018) and vancomycin resistance among Enterococcus faecium isolates (n = 368) were 30.0 and 59.5%, respectively. Multidrug-resistant (MDR) phenotypes (isolates resistant to three or more different chemical classes of antimicrobial agents) accounted for 14.2% of S. pneumoniae isolates, 27.1% of S. aureus isolates, and 58.4% of E. faecium isolates. For all gram-positive species tested, MICs at which 90% of the isolates tested were inhibited (MIC(90)s) and MIC ranges for directed-spectrum agents (daptomycin, quinupristin-dalfopristin, and linezolid) were identical or highly similar for isolates susceptible or resistant to other agents or MDR. Daptomycin had a MIC(90) of 0.12 micro g/ml for both penicillin-susceptible and -resistant isolates of S. pneumoniae. Against oxacillin-resistant S. aureus daptomycin had a MIC(90) of 0.5 micro g/ml, and it had a MIC(90) of 4 micro g/ml against both vancomycin-susceptible and -resistant E. faecium. The MIC(90)s for daptomycin and other directed-spectrum agents were unaffected by the regional or anatomical origin of isolates or patient demographic parameters (patient age, gender, and inpatient or outpatient care). Our results confirm the gram-positive spectrum of activity of daptomycin and that its activity is independent of susceptibility or resistance to commonly prescribed and tested antimicrobial agents. This study may serve as a baseline to monitor future changes in the susceptibility of gram-positive species to daptomycin following its introduction into clinical use.
Critchley
Ian A
IA
Focus Technologies, Inc., Herndon, Virginia, USA.
Blosser-Middleton
Renée S
RS
Jones
Mark E
ME
Thornsberry
Clyde
C
Sahm
Daniel F
DF
Karlowsky
James A
JA
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017576:Daptomycin / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D016984:Enterococcus faecium / Q000187:drug effects; D006094:Gram-Positive Bacteria / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D013211:Staphylococcus aureus / Q000187:drug effects; D013291:Streptococcus / Q000187:drug effects; D014481:United States
D000900:Anti-Bacterial Agents; D017576:Daptomycin