S epidermidis and P aeruginosa are recognised major biofilm pathogens in medical device contamination and chronic wounds. Within biofilms, bacteria are enclosed in a polymeric matrix that cements them to each other and to the surface and protects them by increasing resistance to host immunity, antibiotics and biocides. Staph and pseudomonas spp biofilm were grown on glass coupons for 48 hours and the coupons randomly inserted into the wound model for 24 hours and subjected to TNP and the following: No instillation 0.1% w/v formulated hypocholorous acid (FHA) instillation Saline instillation Betadine instillation Betadine and saline instillations were for 30 minutes, while FHA was for three minutes, every eight, four and two hours per day. The biocides were at sub-lethal concentrations. The coupons were then extracted to avoid damaging the biofilms and effect of TNP was assessed by colony forming units and electron microscopy. The results show that lower frequency of instillation did not have significant effect on bacterial load for both types of bacteria. Increase in frequency of instillations resulted in no growth of pseudomonas while increase in frequency of instillations resulted in a significant decrease in growth of staph spp. Frequent flushing of the wound model resulted in a loss of biofilm bacteria for both Pseudomonas and Staph epi. The biocides combined with TNP were more effective in killing Pseudomonas compared with Staph epi.
