title: The action of Pseudomonas aeruginosa biofilms in intrinsic drug resistance.
abstract: BACKGROUND
  There is a growing interest in studying the relationship between intrinsic resistance and biofilms resistance to drugs. However, the relationship still remains unclear in the macroscopic bacterial growth. Our study is to illuminate the change of bacterial drug resistance of gyrA mutant and active efflux pump during the development of Pseudomonas aeruginosa (P. aeruginosa) biofilms.
  
  
  METHODS
  The strains of type II topoisomerase gene mutant (gyrA mutant) and multidrug resistance (MDR) efflux pump were clinical isolates and detected by polymerase chain reaction (PCR). The process of bacterial biofilms development was observed by scanning electron microscope. Triparental mating experiments were performed to transfer report gene of green fluorescent protein (GFP) into P. aeruginosa biofilms strains and followed by analysis of bacterial survival rate between intrinsic resistance and biofilms resistance.
  
  
  RESULTS
  The fluorescent strains with pGFPuv could develop mature biofilms on Teflon surface. Before a period of 72 hours, the survival rate of biofilms bacteria and intrinsic resistance strains in ciprofloxacin solution was significantly different (P < 0.05). The survival number of intrinsic resistance strains (gyrA mutation and active efflux pump) was illustriously higher than biofilm strain in the initial stage of biofilms development. After 72 hours incubation, there was no clearly difference between mutants and biofilms strains in the survival rate (P > 0.05). The carbonyl cyanide m-chlorophenylhydrazone and azithromycin could significantly reduce the drug resistance of biofilm strains and efflux pump strains.
  
  
  CONCLUSIONS
  In the development of P. aeruginosa biofilms, the strains of gyrA mutation and MDR efflux could be conferred with new level of drug resistance. When co-cultured mutated strains with biofilm strains, biofilms may play a major role in bacterial resistance. But after 72 hours incubation (a mature biofilms had been developed), there was no clearly difference between the number of mutant strains and biofilm strains.
authors.affiliation: Department of Microbiology, College of Basic Medicine and Forensic Medicine, Sichuan University, Chengdu 610041, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Xie
authors.forename: Wen-xiang
authors.initials: WX
authors.lastname: Jia
authors.forename: Wei
authors.initials: W
authors.lastname: Zeng
authors.forename: Wei-qing
authors.initials: WQ
authors.lastname: Yang
authors.forename: Xi
authors.initials: X
authors.lastname: Cheng
authors.forename: Xue-ru
authors.initials: XR
authors.lastname: Li
authors.forename: Lan-lan
authors.initials: LL
authors.lastname: Wang
authors.forename: Mei
authors.initials: M
authors.lastname: Kang
authors.forename: Zai-rong
authors.initials: ZR
authors.lastname: Zhang
mesh_terms: D018441:Biofilms / Q000187:drug effects*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002939:Ciprofloxacin / Q000494:pharmacology; D027081:DNA Gyrase / Q000235:genetics; D024881:Drug Resistance, Bacterial; D009154:Mutation; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics
chemical_list: D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D002939:Ciprofloxacin; D027081:DNA Gyrase