Results of in vitro testing of wound dressings with sustained release of polihexanide (PHMB) and silver ions at different ph values

H Braunwarth, FHH Brill, H Brill

HygMed 2011; 36 [10]: 393–398

Background:

The pH values in acute and chronic wounds differs and changes however during the wound healing process. Until now wound pH values have not been taken into consideration during efficacy testing of antimicrobial wound therapeutics. Therefore, the present study investigated on the influence of the pH value on the antimicrobial potential of silver ions and polihexanide (PHMB).

Method:

We investigated in the agar diffusion assay whether the bacteriostatic efficacy of selected antimicrobial impregnated wound dressings with silver or polihexanide release is influenced by the pH value. The following test organisms were selected: Staphylococcus aureus, Methicillin resistant Staphylococcus aureus (MRSA), Enterococcus faecium and Pseudomonas aeruginosa. Three wound dressings were selected for the tests: Biatain Ag Non Adhesive (foam dressing, Coloplast GmbH, Hamburg), Seasorb Ag (alginate dressing, Coloplast GmbH, Hamburg) and Suprasorb X+PHMB (hydrobalance dressing, Lohmann&Rauscher GmbH&Co. KG, Neuwied)

Results:

The polihexanide containing dressing did not show bacteriostatic efficacy (inhibition zone =) at acid ph values (ph 5.5) for all test organism. At pH 6.0 no bacteriostatic efficacy against MRSA (inhibition zone 0.3 mm), E. faecium and P. aeruginosa (inhibition zone 0 mm) but an efficacy against S. aureus (inhibition zone 1.8 mm) was detected. The test product did not show a bacteriostatic efficacy against S. aureus, MRSA and E. faecium (inhibition zone 1.0–6.8 mm) at neutral (ph 7.0)and alkaline ph value (ph 8.0), but not against P. aeruginosa. However, at pH 9.0 the test product showed an efficacy against all test organisms (inhibition zone 1,5–9,3 mm). The dressings with sustained silver release showed at all pH values an bacteriostatic efficacy (inhibition zone 0.8–5.5 mm). The foam dressing showed a superior efficacy compared to the alginate dressing.

Conclusion:

These results do not allow recommendations for the daily practice in wound care for the time being. Nevertheless our results show, that the bacteriostatic efficacy of antimicrobial wound dressing is influenced by the pH value. This should be taken into consideration in clinical practice.