Objective: To study the antibiotic resistance evolution, homology, phenotypes and genotypes of carbapenemase in Acinetobacter baumannii from clinical isolates.
Methods: A total of 72 strains of Acinetobacter baumannii were isolated from Xiangya Hospital of Central South University from March to May 2012. Antimicrobial susceptibility test was carried out by automatic microorganism clinical analytical system VITEK-II. The homology of the 72 strains was analyzed by enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR). Modified Hodge test was used to screen carbapenemases of the strains. Carbapenemase genes blaOXA-23, blaOXA-40 and blaOXA-58 were also amplified and sequenced.
Results: The 72 strains of Acinetobacter baumannii remained sensitive to cefoperazone/sulbactam (resistance rate 8.33%), followed by Amikacin. Otherwise, they were resistant to most of the antimicrobial agents (resistance rate more than 70%). The 72 strains were identified as 7 epidemic clones, A-G, by means of ERIC-PCR and the phylogenetic relationship among D, E, F and G was very close, suggesting a nosocomial infection possibility. Totally 56 strains produced carbapenemase; 61 strains were positive for carbapenemase gene blaOXA-23 and 1 strain positive for blaOXA-58. All strains were negative for carbapenemase gene blaOXA-40.
Conclusion: Acinetobacter baumannii strains isolated clinically are resistant to most of the antimicrobial agents and nosocomial infection had been observed. Most of the strains produce carbapenemase, among which, blaOXA-23 gene is the main carbapenemase gene. blaOXA-58 gene exists in the Acinetobacter baumannii isolates from Hunan Province.