Abstract: AIM: To evaluate the antibiotic effects in vitro of cefathiamidine combined with 6 antimicrobial agents against Staphylococcus epidermidis. METHODS: The protocol was designed by checkerboard method, the MICs against 30 strains of Staphylococcus epidermidis were determined by broth dilution method, and the FIC index was calculated according to MIC values. RESULTS: The MIC50 of cefathiamidine alone against Staphylococcus aureus was 16 mg·L^-1 and theMIC50 of cefathiamidine combined with 6 antimicrobial agents was reduced to 0.125, 0.125, 0.125, 0.125, 0.25, 0.125 mg·L^-1, respectively.The MIC90 of cefathiamidine alone against Staphylococcus epidermidis was reduced to 1, 1, 1, 2, 1 mg·L^-1, respectively. CONCLUSION: The synergism and additivity are shown when cefathiamidine combined with 6 antimicrobial agents against 30 strains Staphylococcus epidermidis, and the autonomy and antagonism are not found.

Key words: cefathiamidine, Staphylococcus epidermidis, FIC, checkerboard method