Study On Relationship Between Biofiim Formation And Drug-resistance Of Acinetobacter Baumannii

Objective Acinetobacter baumannii is an important pathogen of nosocomial infections, and biofilm plays an important role in adhesion, drug-resistance, response to environment, escape from immunity and so on. We focus on the relationship between biofilm formation and drug-resistance in Acinetobacter baumannii from clinics and to provide a theoretical basis for precaution and therapy of Acinetobacter baumannii infections.Methods The isolated Acinetobacter baumannii strains were identified by MicroScan WalkAway automatic identification systems. The strains were cultured by LB. and grouth curves were detemined to determin the log phase.96well microtitre plates combined with crystal violet staining were used to test biofilms semi-quantitively. The biofilms of A. baumannii were grown on black polycarbonate membranes and covered by various antibiotic discs. The infiltration of chloramphenicol and ofloxacin was determined by measuring the diameters of growth inhibition zones of Escherichia coli ATCC25922on Mueller-Hinton agar plates. We selected TEM gene associated with drug-resistant to β lactamase. adeB gene which encoded efflux pump. OXA-23gene which associated with drug-resistant to carbapenem and cat gene response to drug-resistant to chloramphenicol. PCR was conducted to detect the4genes in strains. Real-Time PCR was used to detect the different expressions of the4genes in biofilm and their planktonic counterparts.Results All strains of A. baumannii isolated from clinics are muti-drug resistant, and can form biofilm in vitro. No.2strain form less biofilm than the other strains. Accoding to Rachna Singh, we established the method with black polycarbonate membranes to test the infiltration limitation of bioflms. Except for No.85. all the other isolates can limit the infiltration of chloramphenicol through biofilms. while there were no difference under ofloxacin exposure compare to control groups. The PCR indicated that all strains possessed TEM gene and cat gene:except for No.65and No.10. the other strains possessed adeB gene, and only No.67and No.78expressed OXA-23gene. Real-Time PCR indicated that all4different genens expessed lower in biofilm than in planktonic.Conclusion The findings showed that all the multi-drug resistant strains of A. baumannii from clinic can form biofilms in vitro. The results of infiltration limitation test of chloramphenicol and ofloxacin proves that the limiting the infiltration of antibiotics is but not the only reason of drus-resistance of bifilm. The result of PCR and Real-Time PCR indicated that the drug-resistance of biofilm may be not associated with the genes’ different expression.