title: Chlorhexidine activity against bacterial biofilms.
abstract: BACKGROUND
  A biofilm is a complex microbiological ecosystem deposited on surfaces. Microorganisms in form of biofilms are of particular clinical concern because of the poor response to antimicrobial treatments. This study aimed to determine whether bacterial and fungal biofilms are able to resist the antimicrobial activity of chlorhexidine, a powerful antiseptic widely used in the hospital environment.
  
  
  METHODS
  Disk diffusion and susceptibility tests were conducted in accordance with Clinical and Laboratory Standards Institute standards for the determination of biofilm inhibitory concentration. Chlorhexidine was tested first at a minimum inhibitory concentration and then at higher concentrations when it was not able to destroy the biofilm. The plates were developed with a solution of 0.1% crystal violet, and readings were made at an optical density of 570 nm.
  
  
  RESULTS
  Chlorhexidine demonstrated excellent antimicrobial activity for most microorganisms tested in their free form, but was less effective against biofilms of Acinetobacter baumannii, Escherichia coli, methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa.
  
  
  CONCLUSIONS
  This study confirms that microorganisms in biofilms have greater resistance to chlorhexidine, likely owing to the mechanisms of resistance conferred to the structure of biofilms.
authors.affiliation: Graduate Program in Pharmaceutical Sciences, Federal University of Santa Maria (UFSM), Santa Maria, RS, Brazil. Electronic address: pauline-cb@hotmail.com.
authors.forename: Pauline Cordenonsi
authors.initials: PC
authors.lastname: Bonez
authors.forename: Camilla Filippi
authors.initials: CF
authors.lastname: Dos Santos Alves
authors.forename: Tanise Vendruscolo
authors.initials: TV
authors.lastname: Dalmolin
authors.forename: Vanessa Albertina
authors.initials: VA
authors.lastname: Agertt
authors.forename: Caren Rigon
authors.initials: CR
authors.lastname: Mizdal
authors.forename: Vanessa da Costa
authors.initials: Vda C
authors.lastname: Flores
authors.forename: Jaciane Baggiotto
authors.initials: JB
authors.lastname: Marques
authors.forename: Roberto Christ Vianna
authors.initials: RC
authors.lastname: Santos
authors.forename: Marli Matiko
authors.initials: MM
authors.lastname: Anraku de Campos
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects*; D018407:Bacterial Physiological Phenomena / Q000187:drug effects*; D018441:Biofilms / Q000187:drug effects*; D002710:Chlorhexidine / Q000494:pharmacology*; D005658:Fungi / Q000187:drug effects* / Q000502:physiology*; D006801:Humans; D008826:Microbial Sensitivity Tests
chemical_list: D000890:Anti-Infective Agents; D002710:Chlorhexidine
keywords: Biofilms; Chlorhexidine; Microbial resistance