title: In vitro Comparison of Anti-Biofilm Effects against Carbapenem-Resistant Acinetobacter baumannii: Imipenem, Colistin, Tigecycline, Rifampicin and Combinations.
abstract: BACKGROUND
  Multi-drug resistant (MDR) Acinetobacter baumannii has emerged as one of the most important nosocomial pathogens. In addition to the diverse resistance mechanisms, some A. baumannii strains are known to have biofilm-producing capacity, thereby decreasing antibiotic effectiveness.
  
  
  METHODS
  This study was designed to assess biofilm-producing capacity of three different MDR A. baumannii strains with diverse resistance mechanisms (OXA-51, IMP-1 and VIM-2 type β-lactamases), and intended to compare the effect of each antibiotic regimen (rifampicin, colistin, imipenem, tigecycline, rifampicin-imipenem and rifampicin-colistin) on mature A. baumannii biofilms using in vitro polystyrene plate biofilm assay.
  
  
  RESULTS
  Among three MDR A. baumannii strains, only VIM-2 strain produced strong biofilm compared to the controls (optical density, 8.04 ± 2.16 vs. 0.49 ± 0.26). Regarding VIM-2 strains, none of imipenem, colistin and rifampicin reduced biofilm formation alone at MIC of each antibiotic agent (inhibition of biofilm synthesis, less than 30%). In comparison, tigecyclin (0.76 ± 0.23), imipenem-rifampicin (1.07 ± 0.31) and colistin-rifampicin (1.47 ± 0.54) showed a significant inhibition of biofilm synthesis compared to the positive controls at 48 hours after incubation (P<0.01). Tigecycline inhibited biofilm formation even at the one fourth level of MIC (1.17 ± 0.21). Likewise, both imipenem and colistin were also effective even with the reduced concentrations when those were combined with rifampicin. Such biofilm-inhibiting effects with those antibiotic regimens sustained up to 96 hours after incubation.
  
  
  CONCLUSIONS
  Tigecycline, imipenem-rifampicin and colistin-rifampicin would be effective for the prevention or reduction of biofilm formation caused by A. baumannii strains.
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Joon Young
authors.identifier: 0000-0002-0148-7194
authors.initials: JY
authors.lastname: Song
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Hee Jin
authors.identifier: 0000-0002-2532-1463
authors.initials: HJ
authors.lastname: Cheong
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Ji Yun
authors.identifier: 0000-0001-8541-5704
authors.initials: JY
authors.lastname: Noh
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Woo Joo
authors.identifier: 0000-0002-4546-3880
authors.initials: WJ
authors.lastname: Kim
keywords: Acinetobacter baumannii; Anti-bacterial agents; Biofilm
references.citation: Appl Environ Microbiol. 2008 Dec;74(23):7376-82
references.pmid: 18836028
references.citation: Clin Microbiol Infect. 2008 Jan;14(1):49-54
references.pmid: 18005176
references.citation: Int J Antimicrob Agents. 2007 Nov;30(5):415-21
references.pmid: 17768034
references.citation: Clin Infect Dis. 2001 Oct 15;33(8):1387-92
references.pmid: 11565080
references.citation: Clin Infect Dis. 1996 Jun;22(6):1026-32
references.pmid: 8783704
references.citation: J Bacteriol. 2008 Feb;190(3):1036-44
references.pmid: 18024522
references.citation: Clin Microbiol Infect. 2006 Sep;12(9):826-36
references.pmid: 16882287
references.citation: J Antimicrob Chemother. 2007 Aug;60(2):317-22
references.pmid: 17540672
references.citation: FEMS Microbiol Lett. 2006 May;258(1):72-7
references.pmid: 16630258
references.citation: Int J Antimicrob Agents. 2009 Jan;33(1):33-9
references.pmid: 18835761
references.citation: Appl Environ Microbiol. 2006 Jun;72(6):3916-23
references.pmid: 16751497
references.citation: Microb Drug Resist. 2009 Sep;15(3):151-8
references.pmid: 19728771
references.citation: Clin Infect Dis. 1995 Apr;20(4):790-6
references.pmid: 7795075
references.citation: Clin Microbiol Infect. 2008 Mar;14(3):276-8
references.pmid: 18190568
references.citation: Emerg Infect Dis. 2002 Sep;8(9):881-90
references.pmid: 12194761
references.citation: J Clin Microbiol. 2006 Mar;44(3):827-32
references.pmid: 16517861
references.citation: Mol Microbiol. 1997 Jun;24(5):1013-24
references.pmid: 9220008
references.citation: FEMS Immunol Med Microbiol. 2008 Jun;53(1):140-4
references.pmid: 18400015
references.citation: Int J Antimicrob Agents. 2008 Sep;32(3):281-4
references.pmid: 18650070