[In vitro activity of daptomycin and other antimicrobial agents against 499 strains of gram-positive cocci causing bloodstream infection].

OBJECTIVE

To evaluate the in vitro activity of daptomycin, vancomycin, teicoplanin, tigecycline, ceftobiprole and linezolid against 499 strains of blood-isolated gram-positive cocci.

METHODS

Determination of the minimal inhibitory concentration (MICs) of daptomycin with microbrothdilution method and the MICs of other 9 antimicrobial agents with agar dilution method against 499 strains of blood-isolated gram positive cocci was carried out. The data was analyzed with WHONET 5.4 software.

RESULTS

The susceptibility rates of staphylococci to daptomycin, tigecycline, linezolid, ceftobiprole, vancomycin and teicoplanin were 100%. All staphylococcus strains were inhibited by daptomycin at a MIC of 1 mg/L. The MIC(50) and MIC(90) of daptomycin were both 0.5 mg/L against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus coagulase-negative (MRSCoN). Among Enterococcus spp, the highest MIC of daptomycin was 4 mg/L. The MIC(50) and MIC(90) of daptomycin were both 2 mg/L against E.faecalis, whereas they were 2 mg/L and 4 mg/L against E.faecium. One strains of linezolid-resistant E.faecalis (MIC: 8 mg/L) was susceptible to daptomycin (MIC: 1 mg/L). Three strains of E.faecium carrying vanA gene with vancomycin MICs above 32 mg/L and teicoplanin MICs also 32 mg/L were susceptible to daptomycin, tigecycline and linezolid. The MIC range of daptomycin against Streptococcus pneumoniae and Streptococcus viridans was 0.032 - 0.25 mg/L and 0.125 - 1.000 mg/L separately.

CONCLUSIONS

Daptomycin has excellent in vitro activity against common gram-positive pathogens isolated from blood. It may be a good choice for clinicians to treat drug-resistant gram-positive cocci.