Carbapenemase genotypes of imipenem-resistant Acinetobacter baumannii strains

Objective To investigate the carbapenemase genotypes of imipenem-resistant Acinetobacter baumannii.Methods A total of 48 imipenem-resistant Acinetobacter baumanii strains were isolated from Jishuitan Hospital.The minimum inhibitory concentrations (MICs) of isolates to 7 antimicrobial agents were determined by agar dilution.The genes of OXA-23,OXA-24,OXA-51,OXA-58,VIM-type and IMP-type carbapenamases were determined by PCR.Amplified positive carbapenamase genes were analyzed by DNA sequencing.Results Of 48 Acinetobacter baumannii strains,24 were isolated from patients in respiratory ward,12 were isolated from patients in emergency intensive care unit,7 were isolated from patients in ICU,and 5 were isolated from patients in other departments; 42 were isolated from respiratory tract samples.There were 45 OXA-23 positive isolates(93.8％) and 48 OXA-51 positive isolates.OXA-58,OXA-24,VIM and IMP genes were not detected among the isolates.The Acinetobacter baumannii strains had the highest sensitivity-to polymyxin E reaching 87.5％,while the resistant rates to ciprofloxacin,ceftazidime,gentamicin,cefoperazone / sulbactam and piperacillin / tazobactam were higher than 90.0％.Conclusions OXA-51 gene is widely distributed in Acinetobacter baumannii.OXA-23 gene is the main carbapenemase coding genotype in imipenem-resistant Acinetobacter baumannii isolated from Beijing Jishuitan Hospital. Key words: Acinetobacter baumannii;  Carbapenemase;  Genotype