Background:The re-use of colistin (last-resort drug) to treat infections caused by resistant Gram-negative bacteria, has led to the emergence of a serious resistance against colistin. A new transferable plasmid-mediated colistin-resistance gene (mcr-1) has been described globally. Screening for such gene will provide an aiding step to explore the extent of colistin-resistance in Egypt. Objectives: To isolate the causative Gram-negative bacteria from different hospital-acquired (HA) and community-acquired (CA) infections, determine the antibiotic susceptibility pattern of the isolated bacteria, detect colistin-resistance and investigate the existence of mcr-1 gene in colistin-resistant isolates. Methodology: This study was carried out on 400 patients with HA-and CAinfections. Samples were taken from sputum, endotracheal aspirates, bronchoalveolar lavage, surgical and burn wounds, stool and blood. Bacterial isolation and identification were done by standard microbiological methods. Colistin-resistance was assessed by broth macrodilution method, then mcr-1 gene was detected in colistin-resistant isolates by conventional polymerase chain reaction (PCR). Results: Gram-negative organisms were the commonest isolates in both HA (67.6%) and CA (79.4%) infections. Colistinresistance was detected in only 10 cases. mcr-1 gene was not detected in any of the tested colistin-resistant isolates. Conclusion: The prevalence of colistin-resistance in the study cases is still low and has not extended to the community yet. Colistin intake is not a prerequisite for the occurrence of resistance, but could be a supporting factor.

Background: Metal nanoparticles synthesized by various chemical reactions have significantly gained worldwide interest for their use in biomedical applications. These processes exhibit a broad range of toxicity in none target organisms. To avoid the chemical toxicity, green synthesis of metal nanoparticles is proposed as a cost-effective and eco-friendly alternative. Aloe vera (A. vera) leaf extract is a medicinal agent with multiple properties including antibacterial effect. Its constituents include lignin, pectin and hemicellulose which can be used in the reduction of silver ions to produce silver nanoparticles (AgNPs). Objective: The aim of this article is to study the use of naturally occurring compounds as a reducing and stabilizing agent for the biosynthesis of nanoparticles and to investigate the insecticidal activity of these compounds against Musca domestica (M. domestica) larvae. Methods: Phytochemical analysis of A. vera gel extract was performed and the phytochemical components identified by Gas chromatography–mass spectrometry (GC-MS) analysis. AgNPs and encapsulated chitosan nanoparticles (CsNPs) were prepared by an eco-friendly method using A. vera gel extract as a reducing and stabilizing agent. A. vera-AgNPs and A. vera encapsulated CsNPs were characterized using Ultraviolet-visible spectrophotometer (UV–vis spectrum), Transmission Electron Microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Then, the insecticidal activity of these compounds was investigated against late second instar larvae of house fly. Results: : The most active ingredients identified by GC-MS analysis were Terpene and Sesquiterpens hydrocarbons. The synthesized AgNPs were spherical with average size about 12-75 nm as revealed by TEM. While encapsulated CsNPs were ranged between 34-75 nm and the shape seems spherical with dark parts confirmed the capsulated plant extract. FTIR and XRD confirmed the successful encapsulation of the gel extract within the chitosan nanoparticles. Results proved the insecticidal potential of the tested compounds against M. domestica larvae and the relative potency of encapsulated CsNPs was nearly 148.51 times more potent than A. vera crude extract whereas, AgNPs was nearly 40.65 times more potent than A. vera crude extract. Furthermore, a prolongation of larval duration and reduction in the percentage pupation and adult emergence were observed. Conclusion: Overall, green-synthesized silver and chitosan nanoparticles are used as a biopesticide for house fly control through safer and cost-effective approach.

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http://eajbsf.journals.ekb.eg/ Efficacy of Methanol Leaf Extract, Biosynthesized Silver and Chitosan Nanoparticles Using Nerium oleander against Musca domestica

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