A surveillance study of antimicrobial resistance of gram-positive cocci strains isolated from 16 teaching hospitals in China in 2012
Objective To investigate antimicrobial resistance among gram-positive cocci strains in China in 2012.Methods From June 2012 to December 2012,1790 consecutive and non-repetitive grampositive cocci strains were collected from 16 teaching hospitals.The minimal inhibitory concentrations (MICs) of antibacterial drugs were determined by agar dilution method.A retrospective study was conducted on the rates of resistance to antimicrobial agents.Data was analyzed using chi-square test.Results The prevalence of methicillin-resistant Staphylococcus aureus(MRSA) and methicillin-resistant coagulase-negative Staphylococci (MRCoNS) were 43.6％ (264/605) and 75.7％ (227/300),respectively.The prevalence of MRSA ranged from 20.5％ to 60.9％ in different regions.About 54.4％ (106/195) of Staphylococcus aureus from respiratory tract specimens,43.6％ (58/133) of Staphylococcus aureus from blood samples,and 29.8％ (56/188) of Staphylococcus aureus from wound and pus were resistant to methicillin.The prevalence of MRSA in elder patient group (53.9％,110/204) was higher than that in the younger adult patients (41.4％,149/360) (P＜0.05).The susceptible rates of MRSA to chloramphenicol and SXT were 92.4％(244/264) and 89.8％ (237/264),respectively.Susceptibility of MRSA to gentamycin,erythromycin,clindamycin,tetracyclines,rifampicin and quinolones were ranged from 12.5％ to 51.9％.One vancomycin-intermediate Staphylococcus aureus (VISA) was found in this study.All Staphylococci isolates were susceptible to teicoplanin,vancomycin,linezolid,daptomycin and tigecycline.The prevalence of penicillin-resistant Streptococcus pneumoniae (PRSP) in children below 3 years-old (61.2％,49/80) was higher than that in adult patients (40.2％,90/224) (P＜0.05).About 93.6％ (292/312) and 86.2％ (269/312) of S.pneumonia were resistant to erythromycin and clindamycin,respectively.Penicillin still showed a very high activity against Streptococcus spp.β-Hemolytic group,but more than 60％ of Streptococcus spp.β-hemolytic group were resistant to erythromycin,clindamycin and tetracyclines.Four vancomycin-resistant enterococcus (VRE) strains were found in this study.All Enterococcus isolates were susceptible to daptomycin and tigecycline,and 96.9％ (157/162) of E.faecalis and 99.3％ (150/151) of E.faecium were susceptible to line()dd.About 51.9％ (84/162) of E.faecalis and 61.6％ (93/151) of E.faecium were resistant to high concentration gentamycin.The susceptibility of E.faecalis to all antibiotics except chleramphenicol and tetracycline was higher than that of E.faecium.Conclusion The rates of antimicrobial resistance of Gram-positive cocci are different among strains isolated from different age groups or regions.Teicoplanin,vancomycin,linezolid,tigecycline and daptomycin showed very high activity against Gram-positive cocci. 
 
Key words: 
Antimicrobial resistance;  Anti-bacterial drugs;  Gram-positive cocci