[A study of in vitro activity of daptomycin against 2679 Gram-positive cocci].

OBJECTIVE:To evaluate the in vitro activity of daptomycin against 2679 Gram-positive cocci. METHODS:A total of 2679 non-duplicate Gram-positive cocci isolates were collected from 17 teaching hospitals during January, 2010 and December, 2011. The minimal inhibitory concentrations (MICs) of daptomycin and other anti-microbial agents against 4 Gram-positive cocci were determined by micro-broth dilution method and agar dilution respectively. The data of drug susceptibility were analyzed by WHONET5.6 software. RESULTS:Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative Staphylococci (MRSCoN) detection rates were 45.8% and 84.2%, respectively. The susceptibility rates of sulfamethoxazole, chloramphenicol, erythromycin, tetracycline, clindamycin and rifampicin against MRSA were 93.1%, 85.5%, 13.8%, 26.6%, 63.2% and 50.0%, respectively. The susceptibility rates of daptomycin, vancomycin and linezolid against MRSA and MRSCoN were all 100.0%. The daptomycin MIC₅₀ and MIC₉₀ of MRSCoN and MRSA were 0.5 mg/L. The high level gentamicin resistance rate of 513 Enterococci isolates was 56.9%. The susceptibility rates of chloramphenicol and tetracycline were 76.0% and 44.1%, respectively. The susceptibility rates of tigecycline and daptomycin reached 100.0%. The MIC₅₀ and MIC₉₀ of daptomycin against 17 vancomycin-resistant Enterococci (VRE) were both 2 mg/L. The susceptibility rates of daptomycin against Streptococcus pneumoniae and β-hemolytic Streptococcus were 100.0%. The prevalence of penicillin-nonsusceptible Streptococcus pneumoniae (PNSSP) was 63.1%. The MIC₅₀ and MIC₉₀ of daptomycin against PNSSP were 0.125 mg/L and 0.25 mg/L, respectively according to the breakpoint of oral penicillin. The MIC₅₀ and MIC₉₀ daptomycin against β-hemolytic Streptococci were 0.008 mg/L and 0.032 mg/L. CONCLUSIONS:Daptomycin have excellent in vitro activity against common Gram-positive cocci, including multi-drug resistant bacteria. It may be a good choice for clinicians to treat drug-resistant Gram-positive cocci.