Abstract： Objective To investigate the antibacterial effect and acute toxicity of azithromycin L-threonate.Methods The minimal inhibitory concentration(MIC)and minimal bactericidal concentration(MBC) were detected to investigate the antibacterial activity of azithromycin L-threonate by broth dilution method.The mouse infection model was established using Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus.The antibacterial effect and acute toxicity(LD50) of azithromycin were evaluated after intragastric administration of azithromycin L-threonate.Results The MIC50,MIC90,MBC50 and MBC90 of Azithromycin L-threonate against gram-positive cocci,gram-negative cocci and gram-negative bacilli were similar to azithromycin lactobionate.Drug-resistant bacteria were less sensitive to both azithromycin L-threonate and azithromycin lactobionate.The protective rate of 37.5 mg·kg-1azithromycin L-threonate(55%) was significantly higher than that of 37.5 mg·kg-1azithromycin lactobionate(15%) in mice infected with sensitive strains of Staphylococcus aureus.In addition,LD50 valuesof azithromycin L-threonate [(1 308.6±203.2)mg·kg-1] were obviously greater than those of azithromycin lactobionate [(1 193.1±161.4)mg·kg-1](P<0.05).Conclusion The antibacterial activity of azithromycin L-threonate is similar to azithromycin lactobionate.But,low-dose azithromycin L-threonate is more protective against Staphylococcus aureuson and has lower acute toxicity than azithromycin lactobionate.
2011, Vol. 53 
