The Effect Of The Formation Of Biofilm On The Susceptibility Of Pseudomonas Aeruginosa

Objective: To investigate susceptibility of Pseudomonas aeruginosa biofilm strains generating different types ofβ-lactamase to antibacterials in different culture media. And investigate the effect of Pseudomonas aeruginosa biofilms on different genotypesβ-lactamases.Methods: Select P. aeruginosa isolates generateing expanded spectrumβ-lactamases (ESBL), Cephalosporinaseβ-lactamase (AmpC) or Metalloβ-lactamases (MBL), and set up the biofilm moulds in three kinds of media: L-Broth(LB), Tryptic Soy Broth(TSB) and Mueller-Hinton Broth(MHB). Biofilms were established using a modification of the Calgary biofilm device. This technique involved the generation of biofilms on plastic pegs attached to the lids of 96-well microtiter plates; Determine minimal inhibiting concerntration(MIC) and minimal biofilm elimination concerntration (MBEC) to three kinds of antibacterials, which are typically used against Pseudomonas aeruginosain cilinic: Ciprofloxacin. Ceftazidime and Imipenem, with micro-dilution and MBEC^TM-Device method. The clinical Pseudomonas aeruginosa strains known genotype of beta-lactamase of TEM and CARB were collected and induced by three antimictobials: Ciprofloxacin,Ceftazidime and Imipenem to generate beta-lactamases after the biofilms were built. And the differet expression of beta-lactamases were determined in above status by polymerase chain reaction (PCR). The results were statistical analysized with t test and U test.Results: There was no difference in the susceptibility for planktonic strains to antimicrobials, in LB, MHB and TSB media in statistics (P >0.05); While after the formation of biofilms,the biofilm strains could be resistant above 64 times MIC of planktonic strains to Ceftazidime , 16～128 times MIC of planktonic strains to Imipenem, and 4～32 times MIC of planktonic strains to Ciprofloxacin, respectively. And after the formation of bacterial biofilms. there existed different effects of culture media on bacterial susceptibility to Ciprofloxacin and Imipenem different media in statistics: LB