In Vitro and in Vivo Antibacterial Activities of Levofloxacin against Clinic Isolates

Objective To evaluate in vitro and in vivo antibacterial activities of levofloxacin hydrochloride against clinical isolates and compare with levofloxacin and ofloxacin. Methods Minimal inhibitory concentration(MIC) tests were carried out using the broth-dilutions methods.The affecting factors were also determined.Drugs were administered intravenously 1 h after mice were infected intraperitoneally with 1 mL of bacterial suspension.The median effective dose(ED50) was calculated by the probit method. Results Levofloxacin hydrochloride had strong activity against gram-positive bacteria,such as staphylococcus aureus,staphylococcus epidermidis and streptococcus pneumoniae with MIC50s 0.16-0.62 μg·mL-1.It was also active against gram-negative bacteria,such as escherichia coli,proteus and klebsiella pneumoniae with MIC50s 0.31-1.25 μg· mL-1.The antibacterial activity of levofloxacin hydrochloride decreased under acidic condition,increase of serum concentration and bacteria inoculum size.The protective effects of levofloxacin hydrochloride against experimental systemic infections were observed.ED50s of levofloxacin hydrochloride against staphylococcus aureus and escherichia coli were 4.54 and 1.21 mg·kg-1,respectively.Levofloxacin hydrochloride was as active as levofloxacin and was more active than ofloxacin. Conclusion Levofloxacin hydrochloride shows a good activity against clinical isolates,its in vitro antibacterial activities can be changed by pH,serum concentration in culture media and inoculum size.