Analysis Of The Resistant Phenotype And Genotype In Multidrug Resistant Acinetobacter Baumannii

Objective:To investigate the resistance of Acinetobacter baumannii to antibiotics and determine theβ-lactamases of the multidrug resistant A.baumannii and its drug-resistant genes and analyze the homology of the drug-resistant associated genes. Methods:The collected isolates from the hospitals in Tongling city were identified by Vitek32.Susceptibility tests were performed with the Kirby-Bauer agar diffusion method followed by whonet5.3 software.The extended-spectrumβ-lactamases producing strains were confirmed by agar dilution test and three dimentional test.The AmpC enzyme was detected by three dimentional test and the mentalβ-lactamases were determined by synergy test.The genes of TEM,SHV,AmpC,OXA-23,OXA-24, PER,VEB,IMP,VIM and aacC1,aadA1,aphA1,gyrA for these strains were amplified with polymarase chain reaction(PCR) and part of them were sequenced.Pulsed-field gel electrophoresis(PFGE) was used for homologous analysis.Result:1.Over fifty percent of the isolates were found to be resistant to the third and fourth generations of cephalosporins,SMZ,CIP,ATM,and GEN.The resistance rate to CSL is 8.2%whereas the intermediate rate is 44.8%.The resistance to IMP accounts for 2.2%,and 2 isolates are the pan-drug resistant strains.2.29 from the 31 multidrug resistant strains collected in Tongling Hospital showed AmpC enzyme activity,8 strains produced ESBLs(but only 3 detected by K-B confirmed test) and 5 isolates produced MBL enzyme.3.The genes coding for TEM-1,aacA4 and gyrA were found to be in all of the 31 multidrug resistant strains;30 strains have AmpC gene,29 strains have aacC1 and aadA1 gene; OXA-23 gene exists in 3 strains and 2 isolates have PER and aphA1 gene.No SHV,VEB,IMP,VIM and OXA-24 genes were found in all isolates.4.The homologous analysis showed that 27 strains belong to one clone and no obvious difference was noted in another 2 isolates.Conclusions:1.The drug resistant strains of A.baumannii are frequently noted and the IPM resistant strains emerged in Tongling,a middle-sized city in the south valley of Yangzi River.2.AmpC is the predominent enzyme in the multidrug resistant strains.3.Three dimensional tests used to determine the ESBLs are more efficient than K-B method.4.The genes coding for AmpC,TEM-1,aacC1,aacA4 and aadA1 are prevelant in the tested area and the emergence of OXA-23 gene resistant to IPM has become a challenging problem in clinic use of antibiotics.