In vitro antimicrobial efficacy of a silver alginate dressing on burn wound isolates
Abstract
Objective: To test the antimicrobial effectiveness of a silver alginate dressing on opportunistic pathogens, namely meticillin-sensitive Staphylococcus aureus (MSSA) and meticillin-resistant Staphylococcus aureus (MRSA), Klebsiella spp., Enterococcus faecalis, Enterococcus faecium, Pseudomonas aeruginosa, Escherichia coli, Enterobacter sakazakii, Enterobacter cloacae, Serratia marcescens, Chryseobacterium indologenes, Proteus vulgaris and Acinetobacter baumannii.
Method: In total, 40 microorganisms were isolated from patients attending three burn centres in the US and evaluated for their susceptibility to a silver alginate wound dressing, employing a corrected zone of inhibition assay, conducted on Mueller Hinton agar (MHA).
Results: The sizes of the corrected zones of inhibition varied between and within genera. For example, all Acinetobacter baumannii strains were found to be sensitive to ionic silver at PH 7, with a mean of 2.8mm, compared with 3.5mm at PH 5.5. The silver alginate dressing also demonstrated activity on all strains of Enterobacter and Escherichia coli, with susceptibility to the silver alginate dressing enhanced at PH 5.5. For Enterococcus spp. the average corrected zone of inhibition at PH 7 was 3.6mm, versus 4.9mm at pH 5.5. ALL strains of Pseudomonas aeruginosa were found to be sensitive to the silver alginate dressing. The average corrected zone of inhibition was 6.9mm at pH 7, compared with 8mm at pH 5.5. For MRSA and Staphylococcus aureus, it ranged from 4.5mm to 7.5mm at pH 7. When the pH was decreased to 5.5, the corrected zone of inhibition increased.
Conclusion: This study demonstrates the activity of a silver alginate dressing on a wide range of burn isolates, including antibiotic-resistant bacteria, isolated from three different burn centres in the US. It also highlights the possible importance of pH and its potential effects on antimicrobial performance and microbial susceptibility. However, more extensive testing is required to substantiate this.
Conflict of interest: SLP is employed by Advanced Medical Solutions Ltd.
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