Identification Of Aminoglycoside Modifying Enzymea And16S RRNA Methylase Genes From Aminoglycosides-resistant Acinetobacter Baumannii

Objective:To investigate the antibiotic resistance in Acinetobacter baumannii from the2nd hospital of Tianjin Medical University, To investigate aminoglycosides modifying enzymes and genes of16S rRNA methylase in aminoglycoside-resistant Acinetobacter baumannii(Ab). Study resistance mechanism of aminoglycoside antibiotics in order to provide laboratory evidence for the clinical use of antibiotics.Methods:1. Collected136strains of Acinetobacter baumannii from the2nd hospital of Tianjin Medical University, Kirby-Bauer susceptibility method was performed to detect the sensitivity of136strains of Ab to13strains antibiotics, detect the sensitivity of32strains of amikacin-resistant and gentamicin-resistan Ab to Polymyxin B, Tigecycline,etc.2. Eight aminoglycosides modifying enzymes (aac(3)-Ⅰ、aac(3)-Ⅱ、aac(3)-Ⅳ、 aac(6’)-Ib、aac(6’)-Ⅱ、ant(2")-Ⅰ、ant(3")-Ⅰ、aph(3)-Ⅵ) and Six16S rRNA methylase genes (armA, rmtA, rmtB, rmtC, rmtD, nmpA) were detected from the32strains Ab amikacin-resistant and gentamicin-resistant by PCR-based assays.3. PCR products were purified and sequenced.Results:1.136strains of Acinetobacter baumannii susceptibility to Cefperazone-sulbactam、 Piperacillin-tazobactam and Imipenem were88.2%、72.1%、72.1%, Strains resistant to amikacin and gentamicin were30.9%.2.32strains of Ab amikacin-resistant and gentamicin-resistant were resistant to other aminoglycosides antibiotic,30strains were MDRAB,96.9%.3.32strains of Ab amikacin-resistant and gentamicin-resistant susceptibility to Polymyxin B, Tigecycline, Cefperazone-sulbactam, Minocycline was93.8%,81.3%,62.5%,62.5%, the resistant rates other antibiotics were more than81.3%.4.4stains of aminoglycosides modifying enzymes isolates from32strains Ab amikacin-resistant and gentamicin-resistant, aac(3)-Ⅰ(15)、aac(6’)-Ib(32)、 aac(6’)-Ⅱ(32)、ant(3")-Ⅰ(29), no aac(3)-Ⅱ、aac(3)-Ⅳ、ant(2")-Ⅰ、aph(3)-Ⅵ were detected. 5.32strains Ab amikacin-resistant and gentamicin-resistant all carried armA genes, no rmtA,rmtB,rmtC,rmtD and nmpA was detected.Conclusion:1. Acinetobacter baumannii susceptibility to Cefperazone-sulbactam Piperacillin-tazobactam and Imipenem were higher.2. Amikacin-resistant and gentamicin-resistant Acinetobacter baumannii were resistant to Netilmicin and Tobramycin, Amikacin and gentamicin can be used as the screening of antibacterial drugs to aminoglycoside resistance gene.3.96.9%of aminoglycosides-resistant Acinetobacter baumannii were multidrug-resistant Acinetobacter baumannii(MDRAB). MDRAB susceptibility to Polymyxin B, Tigecycline, Cefperazone-sulbactam, Minocycline were higher(62.5%-93.8%).4. Producing aac(3)-Ⅰ、aac(6’)-Ib、aac(6’)-Ⅱ、ant(3")-Ⅰ gene and armA gene existed widely in clinical isolates of aminoglycosides-resistant Acinetobacter baumannii.