Antibacterial properties of a silver chloride-coated nylon wound dressing

Objective-A silver chloride-coated nylon wound dressing (Ag-WD) was evaluated in vitro for antimicrobial activity against five common equine wound pathogens. Study Design-Bacterial susceptibility study. Sample Population-Equine wound pathogens: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Streptococcus equi subspecies zooepidemicus, and Staphylococcus aureus. Methods-An inoculum of each pathogen was incubated directly with Ag-WD and quantitated after 24 to 48 hours of incubation. To determine if bactericidal activity of Ag-WD was contact dependent, an inoculum of E. coli and Staphylococcus aureus was incubated separately from Ag-WD by a filter and quantitated after 18 hours of incubation. Inductively coupled plasma emission spectrometry (ICP) determined the silver concentration of Mueller-Hinton broth containing Ag-WD after 24 hours of incubation. To establish if the rate of bacterial killing by Ag-WD differed from a constant silver concentration, pathogens were exposed to a silver concentration of 6.45 mu g/mL and quantitated after 18 hours. Results-Direct exposure to Ag-WD significantly reduced bacterial numbers after 15 minutes for K. pneumoniae, 30 minutes for E. coli, 1 hour for P. aeruginosa, and 2 hours for S. equi subspecies zooepidemicus and Staphylococcus aureus. Indirect exposure to Ag-WD resulted in greater than or equal to 99.9% and greater than or equal to 90% kill of the inoculum doses of E. coli at 2 hours and Staphylococcus aureus at 18 hours, respectively. Incubation of the pathogens at the constant silver concentration resulted in bacterial killing rates similar to those obtained by incubation with Ag-WD. Conclusions-In vitro, equine pathogens are effectively killed when exposed to Ag-WD, and the rate of bacterial killing by Ag-WD is similar to a constant silver concentration of 6.45 mu g/mL. Clinical Relevance-The in vitro antimicrobial properties of this silver-coated nylon wound dressing are promising for future prevention of equine wound infections. (C)Copyright 1999 by The American College of Veterinary Surgeons.