23.4 Methicillin-resistant Staphylococcus aureus (MRSA): evidence of silver-resistant genes         

Steven L. Percival, PhD; Christine A. Cochrane, PhD; Jia V. Loh, BSc; Emma J. Woods, PhD; ConvaTec Wound Therapeutics GDC

MRSA is an increasing healthcare problem, and is particularly problematic in wounds. Methods available to treat infections colonized with MRSA rely on the use of topical antiseptics such as ionic silver. Despite the recent evidence of silver resistant genes being present in Enterobacter cloacae presence of silver resistant genes in methicillin resistant Staphylococcus aureus (MRSA) has not been investigated. Subsequently, our initial studies were to determine the prevalence of silver resistant genes in MRSA isolated from wounds in both humans and animals. Polymerase chain reaction (PCR) and agarose gel electrophoresis (AGE) were utilized to determine the frequency of 3 sil genes, silE, silP and silS in 52 MRSA's. Analysis of all MRSA's confirmed absence of the silP and silS genes. However, 5% of MRSA strains were found to contain the silE gene. To determine whether the MRSA strains, containing the silE gene, were sensitive to a silver-containing Hydrofiber^ª dressing confocal laser microscopy was employed. Results confirmed that the silver-containing Hydrofiberª dressing was effective in killing all MRSA with and without the silE gene.