Study On The Antibiotic Resistance And Related Genes Of Acinetobacter Clinical Isolates

Objective: To explore the antibiotic resistance correlative molecular mechanisms of Acinetobacter for providing basis to control Acinetobacter related infection.Content: To investigate the antibiotic resistance phenotypes, genotypes, and their correlation of Acinetobacter clinical isolates in Peking University First Hospital. And preliminarily to investigate the stability of resistance related genes and horizontal gene transfer.Methods: The minimal inhibitory concentrations (MICs) of 31 Acinetobacter isolates against 13 antibiotics were determined by agar dilution method and E-test. Antibiotic resistance related genes (aacC1, aacC2, aacA4, OXA-23, PER-1, AmpC, Int1 and Int2) were detected by polymerase chain reaction (PCR). And sequences of the PCR products were analyzed. Strains generated from the same cell clone were cultivated for generations and then were investigated for the stability of resistance related genes. Horizontal gene transfer was investigated by cell-contact HGT experiment and transformation.Results: The Acinetobacter clinical isolates from Peking University First Hospital displayed severe antibiotic resistance. Five kinds of resistance related genes (aacC1, aacA4, PER-1, AmpC and Int1) were found, among which aacC1, AmpC and Int1 were closely correlated with resistance. Sequences of the PCR products had more than 98% similarity to their counterparts in GenBank. Loss of some resistance related genes took place after generations of bacterial cultivation. Transconjugant and transformant were obtained via HGT experiment and transformation.Conclusion: Multidrug resistance was predominant in Acinetobacter isolates. And multidrug resistance genes were carried by Multidrug resistant isolates. Resistance related genes were found with high similarity, which provides hints that these genes be received from other strains of both the same bacterium and different bacteria. The resistance toβ-lactams and to aminoglycosides correlated with the existences of AmpC and aacC1, respectively; while the prevalence of integrase gene Int1 brought about the transfer of multidrug resistance and the clinical spread of multidrug resistant strains. The instability of resistance genes and stability of integrase gene Int1 coexisted in the strains. The investigation of Int1 might probably evaluate and predict the development of multidrug resistance. After further study, it would be a brand-new idea to control the HGT of resistance genes for new-drug screen.