Prevalence of silver resistance genes in bacteria isolated from human and horse wounds
Résumé
The aim of this study was to investigate the prevalence of silver resistance genes in 172 bacterial strains which had been isolated from both human and equine wounds. PCR screening for 8 currently named genes in 3 silver resistance transcriptional units, E, RS and P, CBA and F was performed on total DNA extracted from all clinical isolates. Plasmids were isolated from positive strains to determine if the genes were present on the chromosome. MICs and zone of inhibition assays were utilised to examine phenotypic resistance to silver nitrate and ionic silver. Evidence of silver resistance genes was demonstrated in six strains of , an organism rarely implicated as a primary pathogen in chronic wounds. MIC data showed that all strains were inhibited at silver nitrate concentrations ≥5mg/L. When tested against a silver-containing absorbent wound dressing all strains showed inhibition of growth after 24h. In MIC and zone of inhibition studies, inhibition was evident but reduced in strains which contained genes. Although genes were found in six of the wound isolates studied, the genes were consistently associated with a non-pathogenic bacterium. Furthermore, investigation of phenotypic resistance in -positive isolates showed that silver continued to be effective.
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