In Vitro Activity of Sixteen Drugs Against Staphylococcus Aureus, Enterococcus Faecalis and Enterococcus Faecium: A Multicentre Cross-sectional Study in China

  Objective  To evaluate the in vitro antimicrobial activities of 16 common agents against Staphylococcus aureus, Enterococcus faecium and Enterococcus faecalis to provide data for the rational clinical use of drugs.

  Methods  From 1st January to 31st December in 2019, Staphylococcus aureus, Enterococcus faecium and Enterococcus faecalis were collected from 24 hospitals in 18 provinces in China. Antimicrobial susceptibility testing was conducted by automated instrumentation method, and WHONET 5.6 software was used to calculate the drug sensitivity results of the strains to 16 antibacterial drugs including vancomycin, norvancomycin, fusidic acid and linezolid.

  Results  A total of 255 strains of Staphylococcus aureus, 117 strains of Enterococcus faecalis and 114 strains of Enterococcus faecium were collected. Blood was the most common specimen type (22.2%, 108/486), followed by urine (18.9%, 82/486). According to the drug sensitivity results, vancomycin, norvancomycin, linezolid and teicoplanin maintained high activity to all strains. All Staphylococcus aureus and Enterococcus faecalis were sensitive to vancomycin and teicoplanin, while the resistance rates of vancomycin and teicoplanin against Enterococcus faecium were 4.4% and 2.6%, respectively. The resistance rates of linezolid against Staphylococcus aureus, Eenterococcus faecium and Eenterococcus fascalis were 0, 0 and 4.3%, respectively. Norvancomycin and vancomycin showed similar antibacterial activity against Staphylococcus aureus, Enterococcus faecium, and Enterococcus faecalis, with 50% minimum inhibitory concentration (MIC₅₀) of 1 mg/L, and MIC₉₀ of 2 mg/L. The isolation rate of methicillin-resistant Staphylococcus aureas(MRSA) was 35.7%, with 13.2% resistance to fusidic acid and 3.0% in methicillin-susceptible Staphylococcus aureas.

  Conclusions  The activity of the 16 antimicro-bial drugs against Staphylococcus aureus, Enterococcus faecium and Enterococcus faecalis varied considerably. The data will provide reference for the rational use of antimicrobial drugs.