Chlorhexidine activity against bacterial biofilms

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. Conclusion: 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. Copyright (C) 2013 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.