title: Minimum inhibitory (MIC) and minimum microbicidal concentration (MMC) of polihexanide and triclosan against antibiotic sensitive and resistant Staphylococcus aureus and Escherichia coli strains.
abstract: BACKGROUND
  An in-vitro study was conducted investigating the antimicrobial efficacy of polihexanide and triclosan against clinical isolates and reference laboratory strains of Staphylococcus aureus and Escherichia coli.
  
  
  METHODS
  The minimal inhibitory concentration (MIC) and the minimal microbicidal concentration (MMC) were determined following DIN 58940-81 using a micro-dilution assay and a quantitative suspension test following EN 1040. Polihexanide was tested in polyethylene glycol 4000, triclosan in aqueous solutions.
  
  
  RESULTS
  Against all tested strains the MIC of polihexanide ranged between 1-2 µg/mL. For triclosan the MICs varied depending on strains ranging between 0.5 µg/mL for the reference strains and 64 µg/mL for two clinical isolates. A logRF >5 without and logRF >3 with 0.2% albumin burden was achieved at 0.6 µg/mL triclosan. One exception was S. aureus strain H-5-24, where a triclosan concentration of 0.6 µg/mL required 1 minute without and 10 minutes with albumin burden to achieve the same logRFs. Polihexanide achieved a logRF >5 without and logRF >3 with albumin burden at a concentration of 0.6 µg/mL within 30 sec. The exception was the North-German epidemic MRSA strain, were an application time of 5 minutes was required.
  
  
  CONCLUSIONS
  The clinical isolates of E. coli generally showed higher MICs against triclosan, both in the micro-dilution assay as well in the quantitative suspension test than comparable reference laboratory strains. For polihexanide and triclosan strain dependant susceptibility was shown. However, both antimicrobial compounds are effective when used in concentrations common in practice.
authors.affiliation: Clinical Institute for Hospital Hygiene, Medical University of Vienna, Vienna, Austria.
authors.forename: Ojan
authors.initials: O
authors.lastname: Assadian
authors.forename: Katrin
authors.initials: K
authors.lastname: Wehse
authors.forename: Nils-Olaf
authors.initials: NO
authors.lastname: Hübner
authors.forename: Torsten
authors.initials: T
authors.lastname: Koburger
authors.forename: Simone
authors.initials: S
authors.lastname: Bagel
authors.forename: Frank
authors.initials: F
authors.lastname: Jethon
authors.forename: Axel
authors.initials: A
authors.lastname: Kramer