All chronic
wounds are colonised by bacteria; for some, colonisation progresses to become
infection.
Alginate wound dressings are used for highly exuding chronic
wounds as they are very absorbent, taking up large quantities of exudate while maintaining a moist
wound bed to support healing. Some
alginate dressings are doped with antimicrobials, most commonly
silver, but evidence regarding the efficacy of these is largely inconclusive. This manuscript describes the development and in vitro assessment of
alginate materials doped with
chlorhexidine hexametaphosphate (CHX-HMP), a sparingly soluble
salt which when exposed to aqueous environments provides sustained release of the common
antiseptic chlorhexidine. Comparator materials were a commercial
silver alginate dressing material and an
alginate doped with
chlorhexidine digluconate (CHXdg). CHX-HMP
alginates provided a dose-dependent CHX release which was sustained for over 14 days, whereas CHXdg
alginates released limited CHX and this ceased within 24 h. CHX-HMP and
silver alginates were efficacious against 5 major
wound pathogens (MRSA, E. coli, P. aeruginosa, K. pneumoniae, A. baumannii) in a total viable count (TVC) and an
agar diffusion zone of inhibition (ZOI) model. At baseline the
silver alginate was more effective than the CHX-HMP
alginate in the TVC assay but the CHX-HMP
alginate was the more effective in the ZOI assay. After 7 days' artificial aging the CHX-HMP
alginate was more effective than the
silver alginate for four of the five bacteria tested in both assays. These materials may ultimately find application in the development of
wound dressings for chronic
wounds that provide sustained antimicrobial protection.