In vitro antimicrobial effects of chlorhexidine diacetate versus chlorhexidine free base dressings

Abstract

The aim of this study was to investigate the in vitro antimicrobial performance of a chlorhexidine diacetate dressing and a chlorhexidine free base dressing to determine if the free base form of chlorhexidine has the potential to be an effective alternative to the chlorhexidine salts used in conventional, chlorhexidine-based antimicrobial dressings. Dressing samples were inoculated with clinically relevant pathogenic microorganisms including Gram-positive and Gram-negative bacteria, yeasts and fungus, and subsequently evaluated for in vitro log10 reduction at 1-, 3-, and 7-day time points. Chlorhexidine mole content was also calculated as a function of dressing surface area for both sample types to allow for formulation-independent comparison between the dressings. The chlorhexidine free base dressing demonstrated >0.5 log10 superior mean antimicrobial efficacy at 67% of the experimental time points and equivalent mean antimicrobial efficacy (≤0.5 log10 different) at the remaining time points when compared with the chlorhexidine diacetate dressing. The chlorhexidine free base dressing was also found to contain 36% less chlorhexidine mole content than the chlorhexidine diacetate dressing. Our results suggest that a dressing formulated with chlorhexidine free base can deliver in vitro antimicrobial performance at both a magnitude and rate that meets or exceeds that of a chlorhexidine diacetate-based dressing, while also allowing for a reduction in total chlorhexidine content per dressing. These findings could be of particular interest to researchers developing new antimicrobial technologies as well as to infection preventionists when evaluating antimicrobial products for use on clinical patients at elevated risk of infection.