About Chlorhexidine: Resistance
With the rise in drug resistant organisms such as methicillin-resistant Staphylococcus aureus (MRSA) and the inappropriate and over use of antibiotics, the question of bacterial resistance to chlorhexidine comes to mind. To date there are no reports of a chlorhexidine-resistant strain of bacteria or fungus in the clinical setting despite its use in healthcare for almost 60 years.10 Chlorhexidine is highly potent, fast-acting and usually bactericidal in concentrations in which it is used in clinical settings. It is unlikely that a resistant strain would arise due to chlorhexidine's MOA. Chlorhexidine's nonspecific bactericidal MOA is most likely responsible for its broad spectrum of effectiveness and lack of resistance.
Some researchers have tried to create resistant organisms to chlorhexidine in vitro.25 Although they have had limited success doing this in a Petri dish, the results cannot be applied to clinical use since the concentrations of the chlorhexidine used were significantly below the clinical concentrations of chlorhexidine used.
The World Health Organization (WHO) points out that when these "resistant" organisms were exposed to normal clinical or in-use concentrations, the organisms were susceptible to the antimicrobial effects of the chlorhexidine.24