Abstract: Objective To investigate the gene homology of Acinetobacter baumannii clinical isolates in Renji Hospital and to demonstrate the role of enterobacterial repetitive intergenic consensus (ERIC)-polymerase chain reaction (PCR) on genotyping of Acinetobacter baumannii. Methods The minimum inhibitory concentrations (MIC) of common clinical antibiotics against 81 isolates of Acinetobacter baumannii were determined by agar dilution method. ERIC-PCR was used to type 81 isolates of Acinetobacter baumannii. Pulsed-field gel electrophoresis (PFGE) as reference standard was used to further type 43 imipenem-resistant Acinetobacter baumannii. The practicability of ERIC-PCR was verified. Results The 81 isolates of Acinetobacter baumannii were commonly resistant to 13 antibiotics. The lowest resistant rate was 30.9% for polymyxin, the second was 53.1% for imipenem, and the others were all >60%. The 81 isolates of Acinetobacter baumannii were classified into 6 types by ERIC-PCR, named genotype A, B, C, D, E and F. There mainly were A, B and C genotypes. The 43 imipenem-resistant Acinetobacter baumannii belonged to 3 genotypes, including genotype A had 41 isolates (29 isolates of type A1 and 12 isolates of type A2), genotype B had 1 isolate, and genotype C had 1 isolate. There mainly were 5 PFGE pulsotypes for the 43 isolates, pulsotype A had 34 isolates (31 isolates of type A1 and 3 isolates of type A2), pulsotype B had 6 isolates, and C, D and E types had 1 isolate for each. Conclusions There has been clonal spread of Acinetobacter baumannii among patients in the hospital, which mainly were imipenem-resistant Acinetobacter baumannii. The ERIC-PCR is a useful and expeditious method for genotyping of Acinetobacter baumannii, and the results are correlated with those of PFGE.

Key words: Acinetobacter baumannii, Enterobacterial repetitive intergenic consensus, Polymerase chain reaction, Pulsed-field gel electrophoresis, Homology