Abstract:

Objective To evaluate the accuracy of VITEK 2 Compact automated microorganism analysis system for the determination of imipenem-resistant Acinetobacter baumannii to amikacin,and to investigate the existence of 16S rRNA methylase gene. Methods The drug susceptibilities of 72 isolates of imipenem-resistant Acinetobacter baumannii and 15 isolates of imipenem-sensitive Acinetobacter baumannii to amikacin were determined by VITEK 2 Compact,Kirby-Bauer method and E-test. 16S rRNA methylase armA gene was determined by polymerase chain reaction（PCR）.Results Among the 72 isolates of imipenem-resistant Acinetobacter baumannii,the drug susceptibility results were consistent between Kirby-Bauer method and E-test. The minimal inhibitory concentration （MIC）of 69 isolates was 4-≥64 μg/mL by VITEK 2 Compact,while the results of Kirby-Bauer method and E-test showed being resistant. The MIC of 3 isolates were ≤2 μg/mL by VITEK 2 Compact,while there were 2 isolates being sensitive by Kirby-Bauer method and E-test. The resistant double-ring phenomenon was found in 59 isolates. The positive rate of carrying armA gene was 92.9% （65/70）by Kirby-Bauer method and E-test. Among the 15 isolates of imipenem-sensitive Acinetobacter baumannii,the MIC to amikacin was ≤2 μg/mL,and the results were in accordance with those of Kirby-Bauer method and E-test. Conclusions VITEK 2 Compact is not reliable for the determination of imipenem-resistantAcinetobacter baumannii to amikacin. The resistant double-ring phenomenon might be related with carrying armA gene.

Key words: Acinetobacter baumannii, Imipenem, Amikacin, armA gene