Experimental infection and hydrogel dressings

The prolonged use of a hydrogel (polyacrylamide) dressing on circular 1 cm skin defects was tested in a rat experimental model. The rate of healing and changes in bacterial content following inoculation of 1 X 10(8) Staphylococcus aureus, Escherichia coli or Pseudomonas aeruginosa were measured. Wounds inoculated with Staph. aureus or E. coli prior to polyacrylamide occlusion did not have delayed wound contraction and healing and numbers of organisms were falling at 10 days. Wounds inoculated with Ps. aeruginosa showed a delay in healing with a large increase in organisms (greater than 1 X 10(10] after 10 days occlusion. Prolonged wound occlusion by hydrogel dressings may aid in healing by secondary intention but the presence or growth of pseudomonas indicates that frequent changes of dressings should be made.