The increasing threat of silver-resistance in clinical isolates from wounds and burns

The increasing threat of silver-resistance in clinical isolates from wounds and burns Alaa El-Dien MS Hosny,1 Salwa A Rasmy,1 Dina S Aboul-Magd,2 Mona T Kashef,1 Zeinab E El-Bazza21Microbiology and Immunology Department, Faculty of Pharmacy, Cairo University, Cairo, Egypt; 2Drug Radiation Research Department, National Center for Radiation Research and Technology, Atomic Energy Authority, Cairo, EgyptPurpose: The widespread use of silver-containing compounds has led to emergence of silver-resistant bacteria. Few studies are available on the detectability of plasmid-mediated silver-resistance in developing countries. Therefore, we aimed to detect silver-resistance in isolates from wounds and burns, and to genetically characterize plasmid-mediated silver-resistance genes (sil genes).Methods: One hundred and fifty clinical isolates were obtained from burns and wounds. They were identified using the suitable Analytical Profile Index and MicroScan identification systems. Their antimicrobial susceptibility was tested by the disk diffusion and broth microdilution methods. Their silver nitrate (AgNO3) minimum inhibitory concentration (MIC) was determined using the broth macrodilution method. The presence of different sil genes on plasmids extracted from silver-resistant isolates and the replicon types of the extracted plasmids were investigated using polymerase chain reaction (PCR). The ability of these plasmids to impart silver-resistance was tested by transformation.Results: All except two isolates were multidrug-resistant. Nineteen silver-resistant bacterial isolates (12.6%) were detected; with AgNO3 MIC ≥512 μg/mL. They were identified as Klebsiella pneumoniae