Postantibiotic Effect and Postantibiotic sub-MIC Effect of Enrofloxacin and Ciprofloxacin against Staphylococcus aureus

In this study,the methodologies of postantibiotic effects(PAE),postantibiotic sub-MIC effect(PASME) and sub-MIC effect(SME) were established and relevant results of enrofloxacin and ciprofloxacin against Staphylococcus aureus were obtained.At two and four times the MIC,PAEs of enrofloxacin were 1.03 and 1.50 h,and the PAEs of ciprofloxacin at 1/2,1,2 and 4 MIC were 0.51,0.88,1.47 and 1.92 h,respectively.After exposing to the drugs at four times the MIC for 1 hour,the S.aureus suspension continued the exposure to 1/8,1/4 and 1/2 MIC and resulted in average PASMEs of 0.38,1.15 and 12.31 h,respectively,for enrofloxacin and 2.69,10.17 and 12.31 h,respectively,for ciprofloxacin.The SMEs for enrofloxacin at 1/8,1/4 and 1/2 MIC were 0.40,0.91 and 9.44 h,respectively and for ciprofloxacin 0.42,1.14 and 9.02 h,respectively.The results showed that length of PAE,PASME,and SME of the two drugs were in dose-dependent manner,and ciprofloxacin seemed to exhibit longer effects than enrofloxacin against S.aureus.