Currently, researchers turn to natural processes such as using biological microorganisms in order to develop reliable and ecofriendly methods for the synthesis of metallic nanoparticles. In this study, we have investigated extracellular biosynthesis of silver nanoparticles using four Aspergillus species including A. fumigatus, A. clavatus, A. niger, and A. flavus. We have also analyzed nitrate reductase activity in the studied species in order to determine the probable role of this enzyme in the biosynthesis of silver nanoparticles. The formation of silver nanoparticles in the cell filtrates was confirmed by the passage of laser light, change in the color of cell filtrates, absorption peak at 430 nm in UV-Vis spectra, and atomic force microscopy (AFM). There was a logical relationship between the efficiencies of studied Aspergillus species in the production of silver nanoparticles and their nitrate reductase activity. A. fumigatus as the most efficient species showed the highest nitrate reductase activity among the studied species while A. flavus exhibited the lowest capacity in the biosynthesis of silver nanoparticles which was in accord with its low nitrate reductase activity. The present study showed that Aspergillus species had potential for the biosynthesis of silver nanoparticles depending on their nitrate reductase activity.

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IntroductionWidespread inappropriate antibiotic prescribing by healthcare professionals in the hospital setting is a great concern that may cause many undesirable consequences. Adherences to antibiotic guidelines have proven to be a simple and effective intervention to guide the choice of appropriate empiric antibiotic regimens and reduce the unnecessary variations in the practice among practitioners. The objective of this study was to evaluate the prescription patterns of empiric antibiotic therapy in relation to treatment guidelines and the economic burden of discordance with guidelines in a major referral Iranian university hospital.MethodHospital records of hospitalized patients with empiric antibiotic prescription, from September 2016 to February 2017 were reviewed. The process consisted of comparing empiric antimicrobial administration with institutional guidelines for each patient by a clinical pharmacist and an infectious disease specialist to evaluate the appropriate utilization of antibiotics. Adherence to guideline, the cost of antibiotics usage for each patient and the excess cost consequent from discordance with guideline was calculated.ResultsThe most inappropriate prescribed antibiotics were carbapenems and aminoglycosides. Overall guideline adherence was 27.8%. Frequency of antibiotic usage incompatibility with the guidelines on the basis of dosing interval, duration of therapy and drug indication were 31.46%, 29.44% and 19.36%, respectively. General surgery and internal medicine wards had the least and the most inappropriate antibiotic administration, respectively. Totally antibiotic usage cost was 578,959.39 USD (24,316,294,800 Iranian Rials, IRR) for 6 months, which the excess costs of inappropriate antibiotic prescribing, was 471,319.69 USD (19,795,427,225 IRR). The estimated annual excess cost is 942,639.38 USD (39,590,854,450 IRR).ConclusionIn this research, physicians’ adherence with guidelines for empiric antibiotic therapy was low which was led to 471,319.69 USD excess costs. These results urge institution policy makers to develop guidelines to ensure active dissemination and implementation of them to decrease inappropriate antibiotic usage.