Green synthesis of sliver nanoparticles using different bacteria: Do the synthesized nanoparticles differ in their antimicrobial activity

Objectives: Biosynthesis and characterization of silver nanoparticles (AgNPs) from Escherichia coli,Acinetobacter baumannii and Staphylococcus aureus and determination of antimicrobial activityagainst selected pathogens.Methods: E. coli (ATCC 25922), A. baumannii (clinical strain), S. aureus (ATCC 25923) were culturedin nutrient broth medium and used for biosynthesis of AgNPs. AgNO3 concentration, pH, incubationtime and temperature were optimized for AgNP biosynthesis. Antimicrobial activity of the synthesizedAgNPs was studied using the well diffusion assay.Results: All the selected bacteria produced silver nanoparticles at alkaline pH when the concentrationof AgNO3 was greater than 0.3 g/L. The optimum reaction temperature was 60oC. UV-Visiblespectroscopy with a maximum absorbance of approximately 420 - 430 nm confirmed the presence ofAgNPs. AgNPs produced by S. aureus resulted in larger zone of inhibition (ZOI) against the selectedpathogens where AgNPs produced by E. coli showed comparatively smaller ZOI. Gram negativebacteria (E.coli, P. aeruginosa) were more sensitive to AgNPs compared to gram positive bacteria(Methicillin Resistant S. aureus, S. aureus) and fungal species (Candida albicans).Conclusion: AgNPs produced by S. aureus are the most effective among the tested AgNPs while E.coli produced the least effective AgNPs

Mupirocin resistance of <em>Staphylococcus aureus</em> in clinical isolates and nasal carriage isolates

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Human stomach microbiota: Effects on health and disease

The gut microbiota is a complex ecological community, consisting of trillions of microbes which include bacteria, viruses, fungi and protozoa. The stomach was previously considered as a sterile site uninhabited by microbes due to its hostile environmental conditions. Breaking this concept, Helicobacter pylori was the first pathogen reported to inhabit the stomach. Recent studies have suggested that the stomach harbours transient as well as certain commensal bacterial and fungal species. The five major microbial phyla in the stomach have been identified as Firmicutes, Bacteroidetes, Actinobacteria, Fusobacteria and Proteobacteria. The composition of gastric microbiota is dynamic and is affected by several factors.  These include age group, dietary habits, medication use, inflammation of gastric mucosa and H. pylori colonization.  Further, the role of host genetics has recently been studied in maintaining the stomach microbiota. Mutations in host genes may affect the host’s immune response towards commensal bacteria and reduce their number and diversity. The essential multiple roles of gut microorganisms include maintaining homeostasis in the gut, contributing to immune function and extraction of nutrients and energy from our diets.  Loss of the normal balance between the gut microbiota and host has been associated with several abnormal conditions and disorders such as obesity, malnutrition, inflammatory bowel diseases (IBD), neurological disorders, and cancer. In the stomach, the interaction between H. pylori and the gastric microbiota can also influence gastric dis­ease progression. Further studies should focus on addressing the role of gastric dysbiosis in health and disease. Identifying gastric microbiota is essential to understand how the gut microbiota and H. pylori affect health and disease.</p

TiO2 21 nm nanoparticles as a photocatalytic antimicrobial agent against Escherichia coli, Candida albicans and Methicillin resistant Staphylococcus aureus: A comparison

 Objectives: To determine and compare the antimicrobial activity of 21 nm TiO2 nanoparticles against Escherichia colii, Candida albicans and Methicillin resistant Staphylococcus aureus (MRSA).Methods: Titanium dioxide (TiO2) 21 nm anatase nanoparticles (13.9 g/l) were suspended in miliQ (MQ) water, sonicated (35 MHz for 1 hour) and autoclaved. Sterile glass petriplates were treated with TiO2 suspension or sterile MQ(control). Overnight cultures of E.coli MRSA and C. albicans were added to TiO2 coated plates and control plates and kept at room temperature.   Viable counts were obtained by spread plate method at 0 hours and 24 hours; before and after sunlight exposure for 30 minutes.  Colony forming units (CFU) / ml was calculated to determine percentage reduction of CFU in presence of TiO2. Experiments were done in triplicates.Results: TiO2 nanoparticles demonstrated antimicrobial activity against E.coli, MRSA and C. albicans. Estimated percentage CFU reduction in E.coli (13±8.4), MRSA (12±6.6) and C. albicans (36±4.9 ) was observed at 0 hours of contact in the supernatant. The bactericidal effect was enhanced on exposure of the plates to sunlight. Estimated percentage CFU reductions are E. coli (46±7.9), MRSA (99±0.2 ) and C. albicans (99±0.4). The results for 24 hours were (95±1 ), (35±2.1 ) and (83±4 ) reduction for E. coli, MRSA and C. albicans respectively. When the 24 hour plates were exposed to sunlight (99±0.6), (99±0.6) and (99±0.2) reduction was seen for E.coli, MRSA and C. albicans respectively. Conclusion: Anatase 21 nm TiO2 nanoparticles show enhanced antimicrobial activity against the tested microbial strains following photoactivation by sunlight.  Antimicrobial activity against three different types of microbial strains has varying effects

An Integrated Microfluidic Device for Monitoring Changes in Nitric Oxide Production in Single T-Lymphocyte (Jurkat) Cells

A considerable amount of attention has been focused on the analysis of single cells in an effort to better understand cell heterogeneity in cancer and neurodegenerative diseases. Although microfluidic devices have several advantages for single cell analysis, few papers have actually demonstrated the ability of these devices to monitor chemical changes in perturbed biological systems. In this paper, a new microfluidic channel manifold is described that integrates cell transport, lysis, injection, electrophoretic separation, and fluorescence detection into a single device, making it possible to analyze individual cells at a rate of 10 cells/min in an automated fashion. The system was employed to measure nitric oxide (NO) production in single T-lymphocytes (Jurkat cells) using a fluorescent marker, 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM DA). The cells were also labeled with 6-carboxyfluorescein diacetate (6-CFDA) as an internal standard. The NO production by control cells was compared to that of cells stimulated using lipopolysaccharide (LPS), which is known to cause the expression of inducible nitric oxide synthase (iNOS) in immune-type cells. Statistical analysis of the resulting electropherograms from a population of cells indicated a twofold increase in NO production in the induced cells. These results compare nicely to a recently published bulk cell analysis of NO

Synthesis and characterization of new aromatic esters based on 4,16-pregnadiene-6,20-dione skeleton

A series of new aromatic esters based on 4,16-pregnadiene-6,20-dione skeleton, namely 3β-benzoyloxy-4,16-pregnadiene-6,20-dione and 3β-furoyloxy-4,16-pregnadiene- 6,20-dione, which may be good inhibitors for the 5α-reductase enzyme and show high antiandrogenic activity, were synthesized starting from diosgenin. The structures of the steroids were characterized by elemental analysis, 1H NMR, 13C NMR, IR and mass spectrum. Single crystal X-ray diffraction measurement on one of the new compounds, 3β-(p-methoxybenzoyloxy)-4,16-pregnadiene-6,20-dione revealed that the A, B, C, and D ring adopted half chair, distorted chair, distorted chair, and distorted envelope conformation, respectively. The molecules in the crystal were packed face-to-face at the normal van der Waals distances