Abstract: AIM: To investigate the antimicrobial activity of Colistin and other antibiotics against Acinetobacter baumannii. METHODS: The agar dilution method was used to determine the minimum inhibitory concentrations (MICs)of Colistin and other antibiotics against 70 Acinetobacter baumannii collected from PLA General Hospital, Peking Hospital and Beijing Union Hospital.The sensitive rate was judged by CLSI stan-dard. RESULTS: The resistant rates of 70 Acinetobacter baumannii to penicillins and cephalosporins, carbopenems (meropenem and imipenem cilastatin), aminoglycosides(netilmicin and amikacin), fluoroquinolones(ciprofloxacin and levofloxacin)were 71.4 %-82.9 %, 75.7 %-77.1 %, 71.4 %-75.7 %, 32.8 %-82.9 %.Fifty-five multidrug-resistant Acinetobacter baumannii were isolated.All Acinetobacter baumannii in the study were sensitive to Colistin, the MIC50 and MIC90 were both 1 μg mL. CONCLUSION: Acinetobacter baumannii in the study were resistant to many antibiotics including penicillins and cephalosporins, carbopenems, aminoglycosides.Colistin has good antimicrobial activity against Acinetobacter baumannii.

Key words: Colistin, Acinetobacter baumannii, multidrug-resistant, antimicrobial activity