title: The Effect of pH on the Antimicrobial Efficiency of Silver Alginate on Chronic Wound Isolates.
abstract: BACKGROUND
  Nonhealing and stalled chronic wounds are often reported to reside within an alkaline environment. Consequently, a number of researchers have proposed that lowering the pH of a chronic wound environment will enable healing to progress. However, it is not known whether the efficacies of silver-impregnated wound dressings are affected by pH.
  
  
  OBJECTIVE
  To investigate whether pH has an effect on the antimicrobial barrier efficacy of a silver alginate wound dressing on wound isolates.
  
  
  METHODS
  Twenty-five bacteria and yeasts that had been routinely isolated from chronic wounds were separately exposed to a silver alginate wound dressing with the use of a standardized corrected zone of inhibition (CZOI) assay.
  
  
  RESULTS
  The silver alginate dressing demonstrated a broad spectrum of antimicrobial barrier activity within the dressing against all wound isolates. However, at a pH of 5.5, compared with a pH of 7, the antimicrobial barrier activity of the silver alginate dressing significantly increased. For all yeasts the CZOI ranged from 6.25 to 11 mm at a pH of 7. At a pH of 5.5, the CZOI range increased from 8.5 to 12.25 mm. For the Gram-negative isolates, the CZOI ranged from 0.75 to 6.5 mm at a pH 7, compared with a CZOI range of 2.75 to 8 mm at pH 5.5. The CZOI for the Gram-positive isolates, including meticillin-resistant Staphylococcus aureus, ranged from 3 to 7.75 mm at pH 7 and from 4.5 to 11.75 mm at pH 5.5.
  
  
  CONCLUSIONS
  For all isolates tested, excluding one strain of Candida albicans and one vancomycin-resistant Enterococcus strain, lowering pH to 5.5 resulted in an improvement in the antimicrobial barrier activity within the silver alginate dressing. Based on these initial in vitro findings, it is possible to suggest that there may be benefits to maintaining an infected or recalcitrant wound in a slightly acid (pH 5.5) environment. In particular, doing so may lead to an enhanced antimicrobial barrier effect of silver, a quicker reduction in the wound microbial bioburden, and therefore a reduction in the need for prolonged antimicrobial use. However, more in vitro and in vivo studies would be warranted to further substantiate these claims.
authors: West Virginia University, Medical School, Department of Pathology, Biofilm Laboratory, Morgantown, WV, USA.
authors: Will
authors: W
authors: Slone
authors: West Virginia University, Medical School, Department of Pathology, Biofilm Laboratory, Morgantown, WV, USA.
authors: Sara
authors: S
authors: Linton
authors: West Virginia University, Medical School, Department of Pathology, Biofilm Laboratory, Morgantown, WV, USA.
authors: Tyler
authors: T
authors: Okel
authors: West Virginia University, Medical School, Department of Pathology, Biofilm Laboratory, Morgantown, WV, USA.
authors: Linda
authors: L
authors: Corum
authors: West Virginia University, Medical School, Department of Pathology, Biofilm Laboratory, Morgantown, WV, USA.
authors: John G
authors: JG
authors: Thomas
authors: West Virginia University, Medical School, Department of Pathology, Biofilm Laboratory, Morgantown, WV, USA ; Advanced Medical Solutions, Winsford, Cheshire, UK.
authors: Steven L
authors: SL
authors: Percival
keywords: Chronic wounds; Microbiology; Silver; Wound dressings; pH