Screening for silver resistant silE gene in Klebsiella pneumoniae isolated from wound and burn patients

Abstract

Background: Bacteria are one-celled organisms cause various infectious disease. Wound site is more susceptible to the pathogenic bacteria and those bacteria becoming resistant to antibiotic day by day, a serious threat to public health. Silver may be a useful as a prophylactic or therapeutic agent for the prevention of wound colonization by organisms that impede healing, including antibiotic-resistant bacteria. It has been a choice antibacterial for use in wound dressings and therapeutics on account of its acknowledged low toxicity. However, concerns are being raised associated with the overuse of silver and the consequent emergence of silver resistant bacterial strains. In previous study, it was found that isolated Klebsiella pneumoniae (KPN) from nasal swab found to be resistant to silver. The aim of this study is to observe the frequency of KPN in burn and wound infected hospitalized patient of Bangladesh, identify the silver resistant KPN, identify the silE gene in silver resistant KPN strains and determine their MIC for silver. Methodology: Specimens were collected from hospitalized patient admitted in burn and wound unit of Shaheed Suhrawardy Medical College. The samples were used for microbiological culture targeting KPN strains. To confirm KPN colony morphology, Gram staining, biochemical tests and Analytical profile index (API) were performed. Resistance for AgNO3 of the isolated KPN was tested spectrophotometrically by dilution method. Polymerase chain reaction (PCR) using silE gene primers was carried out in Silver resistant KPN strains and further silE gene was confirmed by nucleotide sequencing in PCR positive samples. Finally, MIC of the resistant strains was determined spectrophotometrically using dilution method. Results: A total number of 5 KPN strains were found in 15 collected specimens (burn/wound). Out of 5 KPN 2 strains found resistant in dilution method and PCR results targeting silE gene was also positive for these 2 strains. Product size for silE gene is about 424bp which matched with the primer amplified product (resistant 2 KPN). Nucleotide sequencing and subsequent BLASTn analysis that maximum identity and lower e-value shown in the BLASTn where query cover for KPN was 99% which indicates 99 out of 100 sequence lengths is covered by this search and results indicated that the amplified sequence belongs to the silE subclass. The MIC against silver nitrate was 4 mg/L and 3 mg/L for resistant KPN strains. Discussion and conclusion: From this study, it has been found for the very first time in Bangladeshi perspective establish data based on the frequency of KPN in burn and wound infected hospitalized patient in Bangladesh, identify the silver resistant KPN and determine their MIC for silver and to identify the silE gene in silver resistant KPN strains with a possible evidence. In summary, silver act as antimicrobial agent for wound infection and it is proposed that hygiene should be emphasized and targeted towards those applications that have demonstrable benefits in wound care. It would be appropriate for future studies to determine the actual prevalence of these genes and meet the final purpose of this study to assess the likelihood of widespread resistance to silver and the potential for silver to induce cross-resistance to antibiotics, in light of its increasing usage within the healthcare setting.