In vitro efficacy of a polyhexamethylene biguanide-impregnated gauze dressing against bacteria found in veterinary patients

W R. Lee
Karen M. Tobias
David A. Bemis
Barton W. Rohrbach Dr., University of Tennessee - Knoxville

Abstract

Objective - To evaluate the in vitro efficacy of polyhexamethylene biguanide (PHMB)-impregnated gauze dressing in limiting the growth of bacteria both within and underneath the dressing. Study Design - In vitro study. Methods - Squares of PHMB-impregnated and control gauze were placed on agar plates inoculated with 1 of 11 bacterial species, including 8 multi-resistant organisms. Growth under the gauze was assessed qualitatively after 24-hour incubation. Repeated use of sponges was used to evaluate residual inhibitory activity against Micrococcus lutea and Staphylococcus schleiferi ss. schleiferi. In a second procedure, PHMB-impregnated and control gauze squares were placed in sterile plastic wells and inoculated with 1 of 5 bacterial species, including Pseudomonas spp. and Klebsiella spp. Inhibition of bacterial growth within and underneath the dressing after 24-hour incubation was evaluated by quantifying the numbers of bacteria on the well floor and within each square. Results - PHMB-impregnated gauze provided greater inhibition of growth of 4/4 Gram-positive species and 2/6 Gram-negative species on inoculated plates compared with control gauze. Residual inhibitory activity of PHMB-impregnated gauze was significantly greater against M. lutea on all days and against S. schleiferi ss. schleiferi on days 1 and 4 compared with control. No bacteria were recovered from inoculated PHMB-impregnated gauze squares placed in sterile wells or from the well floor underneath. More than 9*105 colony-forming units (CFU) were recovered from inoculated control samples placed in sterile wells and more than 8.4*104 CFU were recovered from control well floors. Conclusion - PHMB-impregnated gauze dressing, when placed on inoculated agar plates, reduces growth of underlying bacteria, particularly Gram-positive species. Wet-inoculated PHMB-impregnated dressing prevents growth of Gram-positive and Gram-negative bacteria both within and underneath the dressing. Clinical Relevance - PHMB-impregnated dressings may be useful for reducing contamination of underlying wounds by bacterial pathogens.