Investigation On Antibiotic Resistance Of Acinetobacter Baumannii And Molecular Epidemiology, Resistant Mechanism Of Pan-drug Resistant Strains And Control Strategy

ObjectiveThis study was designed to investigate the resistance and homology of car-bapenem - resistant Acinetobacter baumannii and to analyze the resistant mechanism of carbapenem - resistant Acinetobacter baumannii. This study was also designed to evaluate the antibiotic effects of Polymyxin B combined with Ri-fampin against 20 carbapenem - resistant Acinetobacter baumannii.Methods20 strains of carbapenem - resistant Acinetobacter baumannii collected from clinical setting were analyzed by pulsed — field gel electrophoresis ( PFGE ) , typed by isoelectric focusing electrophoresis (IEF) , three dimensional tests. On the carbapenemases produced by these strains, polymerase chain reaction ( PCR), cloning and sequencing methods were performed. Outer membrane proteins were extracted by ultrasound physical method and analyzed by SDS -PAGE. Checkboard method and the MIC of the two antibiotics combined was determined by broth dilution method. FIC was calculated according to MIC results.ResultsThe resistant rates to polymyxin B was 10% , while to other antibiotics were 60% ~ 100%. 20 strains were classified into type A,B,C,D,E. 9 strains be-longed to type A, most of which were from ICU of Second Affiliated Hospital, and respiratory unit of First Affiliated Hospital, China Medical University. All 20 strains produced carbapenemases of pi 6. 7. OXA -23 was determined by PCR and sequencing. The analysis of OMP showed that a protein of 31KD disappeared in some resistant isolates. Antibacterial activity of polymyxin B combined with rifampin against carbapenem - resistant acinetobacter baumannii was syner-gistic and additive.ConclusionThe prevalence of carbapenem - resistant Acinetobacter baumannii in our area was due to nosocomial infection. The prevalence of carbapenem - resistant Acinetobacter baumannii in our area was severe. Metallo - beta - lactamase was not detected. All 20 srains produced OXA - type carbapenemase ( OXA23 ). A protein of 31KD OMP disappeared in some resistant isolates was one of the factors contributing to the resistance of Acinetobacter baumannii. Antibacterial activity of polymyxin B combined with rifampin against carbapenem - resistant acinetobacter baumannii was synergistic and additive.