Analysis of resistant genotypes and homogeneity in multidrug resistant Acinetobacter baumannii from ICU

Objective To investigate the resistance of Acinetobacter(A.) baumannii to antibiotics,to determine the β-lactamases of the multidrug resistant A.baumannii and its drug-resistant genes and to analyze the homology of the drug-resistant associated genes.Methods The collected isolates from one hospital were identified by Vitek32.The susceptibility tests were performed with the Kirby-Bauer agar diffusion method.The extended-spectrum β-lactamases producing strains were confirmed by agar dilution test and three dimentional test.The AmpC enzyme was detected by three dimentional test and the mental β-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 polymerase chain reaction(PCR) and part of them were sequenced.Pulsed-field gel electrophoresis(PFGE) was used for homologous analysis.Results(1) Over 90%(20/22) 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 SCF was 22.7% whereas the intermediate rate was 72.7%.The susceptibility to IMP accounted for 95.5%.(2) 21 strains showed AmpC enzyme activity,5 strains produced ESBLs and 5 isolates produced MBL enzyme.(3) The genes coding for AmpC,TEM-1,aacA4 and gyrA were found to be in all of the 22 strains;21 had aacC1 and aadA1 gene;OXA-23,PER and aphA1 gene existed in 1 strain,respectively.No SHV,VEB,IMP,VIM and OXA-24 genes were found in all isolates.(4) The homologous analysis showed that 20 strains belong to one clone.Conclusion There is one clone in the 22 strains of A.baumannii,coding the genes of AmpC,TEM-1,aacC1,aacA4 and aadA1.AmpC enzyme is predominant.