A study on mutant prevention concentration of cefquinome against Staphylococcus aureus

【Objective】 The minimal inhibitory concentration (MIC) and the mutant prevention concentration (MPC) of cefquinome against Staphylococcus aureus were measured for the rational use in veterinary medicine.【Method】 The MIC and MIC for 99% of input cells (MIC₉₉) of cefquinome against S. aureus were determined by agar two-fold dilution method. The S. aureus strains were enriched in broth, and the bacterial concentrations were adjusted to 10¹⁰ colony forming units (CFU) per milliliter. The MPC of cefquinome against S. aureus was determined by agar plates dilution method, and the selection index (SI) was calculated. 【Result and conclusion】 The MIC, MIC₉₉, MPC and SI (MPC/MIC₉₉) of cefquinome against S. aureus strain ATCC 29213 were 0.5, 0.4 , 1.6 μg/mL and 4, respectively. The MIC₅₀, MIC₉₀, MPC₉₀ and SI (MPC₉₀/MIC₉₀) of cefquinome against S. aureus clinical isolates were 0.50, 1.00, 5.12 μg/mL and 5.12, respectively. The results show that cefquinome has a higher activity against S. aureus and a smaller SI. Resistant mutant strains can be reduced by adjusting the dosage regimen.