Exopolysaccharide-mediated silver nanoparticles produced by <Emphasis Type="Italic">Lactobacillus brevis</Emphasis> NM101-1 as antibiotic adjuvant

A green, simple and effective approach was performed to synthesize potent silver nanoparticles using bacterial exopolysaccharide as both a reducing and stabilizing agent. The formation of nanoparticles was first screened by measuring the surface plasmon resonance peak around 400 nm using UV-vis spectroscopy. The morphology of the synthesized AgNPs was determined using TEM, which indicated that the AgNPs were spherical in shape and with an average size of 11–25 nm. The presence of elemental silver of the AgNPs was confirmed by EDX analysis. The possible functional groups of EPS responsible for the reduction and stabilization of AgNPs were evaluated using FTIR. The EPS reduced AgNPs showed excellent antibacterial, and antibiofilm activities against various human pathogenic bacteria. In addition, the efficiency of AgNPs with various broad-spectrum antibiotics against the tested strains was evaluated. It is evident that, the antibacterial and antibiofilm activities of the selected antibiotics were increased in the presence of AgNPs. The increase in activity was more pronounced for gram-negative bacteria Pseudomonas aeruginosa and E. coli. Interestingly, the combination of antibiotics with AgNPs has significantly increased the membrane protein leakage and ROS generation than antibiotics or AgNPs alone. This work supports that AgNPs can be used to enhance the activity of existing antibiotics against gram-negative and gram-positive bacteria for the treatment of infectious diseases.     

Forage Crop <Emphasis Type="Italic">Lolium multiflorum</Emphasis> Assisted Synthesis of AgNPs and Their Bioactivities Against Poultry Pathogenic Bacteria in In Vitro

Italian ryegrass is one of main feed for livestock animals/birds. It has potential antioxidant metabolites that can improve their health and protect them against various infectious diseases. In this work, we studied synthesis of silver nanoparticles assisted by forage crop Lolium multiflorum as a green synthesis way. Potential antibacterial efficacy of these synthesized nanosized silver nanoparticles against poultry pathogenic bacteria was then studied. Aqueous extract of IRG was used as reducing agent for bio-reduction of silver salt to convert Ag⁺ to Ag⁰ metallic nano-silver. Size, shape, metallic composition, functional group, and crystalline nature of these synthesized silver nanoparticles were then characterized using UV–Vis spectrophotometer, FESEM, EDX, FT-IT, and XRD, respectively. In addition, antibacterial effects of these synthesized AgNPs against poultry pathogenic bacteria were evaluated by agar well diffusion method. UV–Vis spectra showed strong absorption peak of 440–450 nm with differ reaction time ranging from 30 min to 24 h. FESEM measurements revealed particles sizes of around 20–100 nm, majority of which were spherical in shape while a few were irregular. These biosynthesized silver nanoparticles using IRG extract exhibited strong antibacterial activities against poultry pathogenic microorganisms, including Pseudomonas aeruginosa, Salmonella typhi, Escherichia coli, and Bacillus subtilis. Overall results confirmed that IRG plant extract possessed potential bioactive compounds for converting silver ions into nanosized silver at room temperature without needing any external chemical for redox reaction. In addition, such synthesized AgNPs showed strong antibacterial activities against pathogenic bacteria responsible for infectious diseases in poultry.     

Role of reactive oxygen species in the antibacterial mechanism of silver nanoparticles on Escherichia coli O157:H7

In this study, the conditions and mechanism of antibacterial activity of hydrophilic polymer coated silver nanoparticles (AgNPs) against E. coli O157:H7 (CMCC44828) as model pathogen was studied. The AgNPs were coated with amphiphilic polymer that introduced carboxyl groups on the surface to make it water-soluble. The AgNPs were exposed to various treatment conditions of pH and temperature before these were combined with the E. coli. The mechanism of the antibacterial activity was studied through the formation of reactive oxygen species (ROS) that was later suppressed with antioxidant to establish correlation with the AgNPs antimicrobial activity. Studies were carried out at both anaerobic and aerobic conditions. The results indicated that 5 mg/L AgNPs inhibited ~50% of the growth of 10⁶ colony forming units per milliliter (cfu/mL) E. coli cells in liquid Luria–Bertani (LB) medium. This dose-dependent antimicrobial activity was higher at increased temperature (37°C) but was lower when the AgNPs were treated with acid at pH 2 before exposure to the bacteria. It was also established that the conditions of higher antimicrobial effect generated more ROS that was dependent on the presence of oxygen. The antibacterial activity was suppressed in the presence of an antioxidant.     

Extracellular biosynthesis,characterization, optimization of silver nanoparticles (AgNPs) using Bacillus mojavensis BTCB15 and its antimicrobial activity against multidrug resistant pathogens

Abstract

Biosynthesis of metal nanoparticles is an area of interest among researchers because of its eco-friendly approach. Current study focuses at biosynthesis of silver nanoparticles (AgNPs) and optimization of physico-chemical conditions to obtain mono-dispersed and stable AgNPs having antimicrobial activity. Initially Bacillus mojavensis BTCB15 produced silver nanoparticles (AgNPs) of 105?nm. Silver nanoparticles (AgNPs) were characterized by particle size analyzer, UV-Vis Spectroscopy, Fourier transforms infrared spectroscopy (FTIR), Atomic force microscopy (AFM), and X-ray diffraction (XRD). Whereas, under optimal conditions of temperature 55?°C, pH 8, addition of surfactant Tween 20, and metal ion K₂SO₄, about 104% size reduction was achieved with average size of 2.3nm. Molecular characterization revealed 98% sequence homology with Bacillus mojavensis. AgNPs exhibited antibacterial activity at concentrations ranging from 0.5 to 2.5?µg/µl against Escherichia coli BTCB03, Klebsiella pneumonia BTCB04, Acinetobacter sp. BTCB05, and Pseudomonas aeruginosa BTCB01 but none against Staphylococcus aureus BTCB02. Highest antibacterial activity was observed at 0.27?µg/µl and lowest at 0.05?µg/µl of AgNPs indicated by zone of inhibition. Conclusively, under optimum conditions, Bacillus mojavensis BTCB15 was able to produce AgNPs of 2.3?nm size and had antibacterial activity against multi drug resistant pathogens.     

利用Mariannaea sp.HJ菌株胞内提取物合成纳米银及其抗菌特性研究

【目的】近年来,纳米银由于其自身独特的抗菌活性而受到越来越多的关注,有研究表明纳米银是一种广谱的抗菌剂,其对数十种致病微生物都有强烈的抑制和杀灭作用。相较于传统的合成方法而言,具有反应条件温和、环境友好等优势的生物合成法是目前的研究热点。【方法】本研究利用真菌Mariannaea sp. HJ的胞内提取物合成纳米银,并对其合成条件进行优化调控,还进一步考察了合成的纳米银颗粒的抗菌性能。【结果】胞内提取物浓度350 mg/L、AgNO_3浓度5 mmol/L、pH 7.0为菌株HJ胞内提取物合成纳米银的最优条件;TEM图像表明合成的纳米银颗粒主要为球形和伪球形,分散性良好,无明显的团聚现象;XRD表明合成的纳米银晶体结构为面心立方体结构;通过FTIR分析结果推测提取物中的羟基、羧基等官能团可能参与了纳米银的还原和稳定过程。此外,在本实验条件下合成的纳米银颗粒对革兰氏阴性菌Escherichia coli BL21和革兰氏阳性菌Arthrobacter sp. W1都有较好的抗菌活性。【结论】真菌Mariannaea sp. HJ胞内提取物能合成尺寸均一且分散性良好的球形纳米银颗粒,合成的纳米银颗粒在抗菌方面具有潜在的研究价值。     

Biogenic silver nanoparticle synthesis with cyanobacterium Chroococcus minutus isolated from Baliharachandi sea-mouth,Odisha, and in vitro antibacterial activity

The burden from microbial diseases has to be addressed in an increasing pace due to multidrug resistance, causing clinical annoyance, globally. Indeed, employing eco-friendly approaches by green syntheses of nanoparticles with metals/metalloids as antibacterial compounds would be continual and cost-effective. Herein, the synthesis of silver nanoparticles (AgNPs) by aqueous extracts of the cyanobacterium Chroococcus minutus (strain, CRLSUM10), collected from the meeting point of sea and river, East coast of India, are presented; both reducing and stabilizing mediators of the synthesized AgNPs were ascertained, by characteriztion by UV–visible spectrophotometry, XRD, FTIR, SEM and SEM-EDX. Furthermore, synthesized AgNPs had a remarkable antibacterial activity at the lowest dose, 100 mg against pathogenic strains of E. coli and S. pyogenes, rendering those as novel antibacterial agents against ‘upper respiratory tract infection’.     

Mycosynthesis and characterization of silver nanoparticles and their activity against some human pathogenic bacteria

The aim of this study was to biosynthesis silver nanoparticles from the fungus Nigrospora sphaerica isolated from soil samples and to examine their activity against five human pathogenic strains of bacteria viz. Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi and Staphylococcus aureus using disc diffusion method. The synergistic effect of silver nanoparticles in combination with commonly used antibiotic Gentamycin against the selected bacteria was also examined. The synthesized silver nanoparticles from free-cell filtrate were characterized by using UV–Vis spectrophotometer analysis, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). UV–Vis spectrophotometer analysis showed a peak at 420 nm indicating the synthesis of silver nanoparticles, FTIR analysis verified the detection of protein capping of silver nanoparticles while SEM micrographs revealed that the silver nanoparticles are dispersed and aggregated and mostly having spherical shape within the size range between 20 and 70 nm. The synthesized silver nanoparticles exhibited a varied growth inhibition activity (15–26 mm diam inhibition zones) against the tested pathogenic bacteria. A remarkable increase of bacterial growth inhibition (26–34 mm diam) was detected when a combination of silver nanoparticles and Gentamycin was used. A significant increase in fold area of antibacterial activity was observed when AgNPs in combination with Gentamycin was applied. The synthesized silver nanoparticles produced by the fungus N. sphaerica is a promising to be used as safe drug in medical therapy due to their broad spectrum against pathogenic bacteria.     

具有优良抑菌特性乳酸菌的筛选鉴定及活性物质检测

【背景】有益性乳酸菌在人体和动物体内分布极为广泛,是维持胃肠道菌群平衡、提高机体免疫力的主力军。近年来,为了解决禁用抗生素而导致动物发病率不断增高的问题,分析和研究乳酸菌及其所产活性物质的益生特性并开发新型饲料添加剂成为一个重要手段。【目的】本实验旨在从土壤中分离筛选出具有优良抑菌特性的乳酸菌,并对其所产活性物质的特性进行分析评价。【方法】采用溴甲酚紫平板法筛选并结合抑菌能力检测,得到2株具有优良抑菌特性的产酸菌株,分别命名为H-3和H-4。经形态学鉴定及16S rRNA基因序列测定后,对2株菌分别进行生长曲线和产酸量检测;通过排除酸处理、蛋白酶处理和热处理的方法分析2株菌所产抑菌物质的有效成分。【结果】H-3和H-4菌株经初步鉴定为乳酸片球菌(Pediococcus acidilactici),2株菌均具有良好的生长性能及产酸性能。菌株发酵上清液对大肠杆菌(Escherichia coli)、金黄色葡萄球菌(Staphylococcus aureus)、猪霍乱沙门氏菌(Salmonella choleraesuis)、福氏志贺氏菌(Shigella flexneri)均表现出明显的抑...     

Effect of the size and shape of silver nanoparticles on bacterial growth and metabolism by monitoring optical density and fluorescence intensity

In this study, we demonstrate the antibacterial activity of silver nanoparticles (AgNPs), depending on their size and shape, on green fluorescent protein (GFP)-expressing E. coli, which provides a facile, rapid, and noninvasive monitoring system. By measuring optical density and fluorescence intensity in the recombinant E. coli, we found that smaller sized plate-shaped AgNPs presented higher antibacterial activity than larger sized, cubic and spherical AgNPs. In the case of 10 nm spherical AgNPs, the optical density was detectable at 15 ng/mL after 12 h incubation, but the fluorescence intensity was not. On the other hand, smaller-sized AgNPs showed higher toxicity than plate-shaped AgNPs based on the measurement of the optical density and fluorescence intensity. The combined analysis of optical density and fluorescence intensity may be helpful for understanding the effect of various materials, including nano- and organic materials, on recombinant bacteria.     

Effect of gemini surfactant (16-6-16) on the synthesis of silver nanoparticles: A facile approach for antibacterial application

In this report, we describe the effect of Gemini surfactants1, 6-Bis (N, N-hexadecyldimethylammonium) adipate (16-6-16) on synthesis, stability and antibacterial activity of silver nanoparticles (AgNPs). The stabilizing effect of Gemini surfactant and aggregation behavior of AgNPs was evaluated by plasmonic property and morphology of the AgNPs were characterized by UV–vis spectroscopy, Dynamic Light Scattering (DLS), X-ray diffraction (XRD), High resolution transmission electron microscopy (HRTEM) and Energy dispersive X-ray analysis (EDX) techniques. Interestingly, the formation of quite mono-dispersed spherical particles was found. Apart from the stabilizing role, the Gemini surfactant has promoted the agglomeration of individual AgNPs in small assemblies whose Plasmon band features differed from those of the individual nanoparticles. The antibacterial activity of the synthesized AgNPs on Gram-negative and Gram-positive bacterium viz., E. coli and S. aureus was carried out by plate count, growth kinetics and cell viability assay. Furthermore, the mechanism of antibacterial activity of AgNPs was tested by Zeta potential and DLS analysis, to conclude that surface charge of AgNPs disrupts the cells causing cell death.     

Generation of chitin‐derived oligosaccharides toxic to pathogenic bacteria using ChiA74, an endochitinase native to Bacillus thuringiensis

Aims: To demonstrate that an endochitinase (ChiA74) native to Bacillus thuringiensis can be used to generate chitin‐derived oligosaccharides (OGS) with antibacterial activity against a number of aetiological agents of disease, including bacteria that cause diarrhoeal and emetic syndromes in humans. Methods and Results: The intact chiA74 with its cis elements was cloned into high and moderately high copy number Escherichia coli expression vectors. Functionally secreted ChiA74 was produced, and the endochitinase cleaved substrate colloidal chitin to produce OGS with 3, 5 and 6 degrees of polymerization. The enzyme was active for an extended period of incubation (24 h), but its activity showed a decrement of 73% and 87%, respectively, after 24 h of incubation at 37 and 55°C. OGS showed inhibitory activity against Bacillus cereus, Listeria inoccua, E. coli, Staphylococcus xylosus, Salmonella species, Staphylococcus aureus, Pseudomona aeruginosa, Shigella flexneri, and Proteus vulgaris. Conclusions: Endochitinase ChiA74 is able to stably maintain hydrolytic activity during prolonged incubation in a mix reaction with chitin to produce bioactive OGS with inhibitory activity against important food‐borne pathogenic bacteria. Significance and Impact of the Study: This is the first study showing that an endochitinase (ChiA74) native of the most important bioinsecticide used worldwide (B. thuringiensis), but here produced in E. coli, is able to generate chitin‐derived OGS with antibacterial activity against clinically significant food‐borne pathogenic bacteria.     

Nano silver entrapped in phospholipids membrane: Synthesis,characteristics and antibacterial kinetics

Abstract

The antimicrobial property of stabilized silver nanoparticles (AgNPs) with phospholipid membrane was investigated on both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacterial strains. The influence of phospholipid concentrations on antibacterial kinetics actions of AgNPs was studied with two different methodologies in order to understand the bactericidal and bacteriostatic effects. The bacterial inactivation of synthesized AgNPs fitted well to the Chick-Watson model with a high regression coefficient, R² > 0.91. The antibacterial properties of AgNPs depend on the particle size, stabilizer and lecithin concentrations. Only the stabilized AgNPs that have the K_lec/Ag values of 1 and 2 presented the inhabitation zone, while unstabilized AgNPs agglomerated quickly, settled on the wells and did not diffuse in agar. In addition, the specific coefficient of lethality depends on the lecithin concentration. An increase in lecithin concentration caused multilayer creation on the AgNPs' surface and reduced the release of AgNPs which led to low bacterial killing rate.     

Biogenic synthesis of silver nanoparticles: Antibacterial and cytotoxic potential

In green chemistry, the application of a biogenic material as a mediator in nanoparticles formation is an innovative nanotechnology. Our current investigation aimed at testing the cytotoxic potential and antimicrobial ability of silver nanoparticles (AgNPs) that were prepared using Calligonum comosum roots and Azadirachta indica leaf extracts as stabilizing and reducing agents. An agar well diffusion technique was employed to detect synthesized AgNPs antibacterial ability on Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus bacterial strains. Furthermore, their cytotoxic capability against LoVo, MDA-MB231 and HepG2 ca cells was investigated. For phyto-chemical detection in the biogenic AgNPs the Fourier-transform infrared spectroscopy (FT-IR) was considered. Zeta sizer, TEM (Transmission Electron Microscope) and FE-SEM (Field Emission Scanning Electron Microscope) were used to detect biogenic AgNPs’ size and morphology. The current results showed the capability of tested plant extract for conversion of Ag ions to AgNPs with a mean size ranging between 90.8 ± 0.8 and 183.2 ± 0.7 nm in diameter. Furthermore, prepared AgNPs exhibited apoptotic potential against HepG2, LoVo, and MDA-MB 231cell with IC₅₀ ranging between 10.9 and 21.4 μg/ml and antibacterial ability in the range of 16.0 ± 0.1 to 22.0 ± 1.8 mm diameter. Activation of caspases in AgNPs treated cells could be the main indicator for their positive effect causing apoptosis. The current investigation suggested that the green production of AgNPs could be a suitable substitute to large-scale production of AgNPs, since stable and active nanoparticles could be obtained.     

Anti‐infectious activity of synbiotics in a novel mouse model of methicillin‐resistant Staphylococcus aureus infection

The anti‐infectious activity of synbiotics against methicillin‐resistant Staphylococcus aureus (MRSA) infection was evaluated using a novel lethal mouse model. Groups of 12 mice treated with multiple antibiotics were infected orally with a clinical isolate of MRSA at an inoculum of 10⁸ CFU on day 7 after starting the antibiotics. A dose of 400 mg/kg 5‐fluorouracil (5‐FU) was injected intraperitoneally on day 7 after the infection. A dose of 10⁸ CFU Bifidobacterium breve strain Yakult and 10 mg of galactooligosaccharides (GOS) were given orally to mice daily with the antibiotic treatment until day 28. The intestinal population levels of MRSA in the mice on multiple antibiotics were maintained stably at 10⁸ CFU/g of intestinal contents after oral MRSA infection and the subsequent 5‐FU treatment killed all the mice in the group within 14 days. B. breve administration saved most of the mice, but the synbiotic treatment saved all of the mice from lethal MRSA infection. The synbiotic treatment was effective for the treatment of intestinal infection caused by four MRSA strains with different toxin productions. There was a large difference among the six Bifidobacteria strains that were naturally resistant to the antibacterial drugs used. B. breve in combination with GOS is demonstrated to have valuable preventive and curative effects against even fatal MRSA infections.     

Synthesis,characterization and evaluation of antimicrobial and cytotoxic activities of biogenic silver nanoparticles synthesized from <Emphasis Type="Italic">Streptomyces xinghaiensis</Emphasis> OF1 strain

We report synthesis of silver nanoparticles (AgNPs) from Streptomyces xinghaiensis OF1 strain, which were characterised by UV–Vis and Fourier transform infrared spectroscopy, Zeta sizer, Nano tracking analyser, and Transmission electron microscopy. The antimicrobial activity of AgNPs alone, and in combination with antibiotics was evaluated against bacteria, namely Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis, and yeasts viz., Candida albicans and Malassezia furfur by using micro-dilution method. The minimum inhibitory concentration (MIC) and minimum biocidal concentration of AgNPs against bacterial and yeast strains were determined. Synergistic effect of AgNPs in combination with antibacterial and antifungal antibiotics was determined by FIC index. In addition, MTT assay was performed to study cytotoxicity of AgNPs alone and in combination with antibiotics against mouse fibroblasts and HeLa cell line. Biogenic AgNPs were stable, spherical, small, polydispersed and capped with organic compounds. The variable antimicrobial activity of AgNPs was observed against tested bacteria and yeasts. The lowest MIC (16 µg ml^?1) of AgNPs was found against P. aeruginosa, followed by C. albicans and M. furfur (both 32 µg ml^?1), B. subtilis and E. coli (both 64 µg ml^?1), and then S. aureus and Klebsiella pneumoniae (256 µg ml^?1). The high synergistic effect of antibiotics in combination with AgNPs against tested strains was found. The in vitro cytotoxicity of AgNPs against mouse fibroblasts and cancer HeLa cell lines revealed a dose dependent potential. The IC₅₀ value of AgNPs was found in concentrations of 4 and 3.8 µg ml^?1, respectively. Combination of AgNPs and antibiotics significantly decreased concentrations of both antimicrobials used and retained their high antibacterial and antifungal activity. The synthesis of AgNPs using S. xinghaiensis OF1 strain is an eco-friendly, cheap and nontoxic method. The antimicrobial activity of AgNPs could result from their small size. Remarkable synergistic effect of antibiotics and AgNPs offer their valuable potential in nanomedicine for clinical application as a combined therapy in the future.     

Green synthesis of silver nanoparticles using Pongamia pinnata seed: Characterization,antibacterial property,and spectroscopic investigation of interaction with human serum albumin

In recent years, green synthesized nanoparticles from plant extract have drawn a great interest due to their prospective nanomedicinal application. This study investigates a proficient, safer, and sustainable way for the preparation of AgNPs using medicinal plant Pongamia pinnata (family: Leguminoseae, species: Pinnata ) seeds extract without using any external reducing and stabilizing agent. Both ultraviolet‐visible spectrum at λ_max = 439 nm and energy dispersive X‐ray spectra proof the formation of AgNPs. An average diameter of the AgNPs was 16.4 nm as revealed from transmission electron microscope. Hydrodynamic size (d  = ~19.6 nm) was determined by dynamic light scattering (DLS). Zeta potential of AgNPs was found to be −23.7 mV, which supports its dispersion and stability. Fourier transform infrared study revealed that the O ─ H, C ═ O, and C‐O‐C groups were responsible for the formation of AgNPs. The antibacterial activity of the synthesized AgNPs was checked against Escherichia coli ATCC 25922. AgNPs at its LD₅₀ dose exhibited synergistic effect with ampicillin. Because protein‐AgNPs association greatly affects its adsorption, distribution, and functionality and can also influence the functions of biomolecules. So in order to understand the adsorption and bioavailability, we investigated by fluorescence, ultraviolet‐visible, and circular dichroism spectroscopic methods the interaction of synthesized AgNPs toward human serum albumin. The binding affinity and binding sites of human serum albumin toward AgNPs were measured by using the fluorescence quenching data. The circular dichroism spectroscopic results revealed that there was a negligible change of α‐helical content in their native structure. Overall, these AgNPs show versatile biological activities and may be applied in the field of nanomedicine.     

Synthesis and comparative study on the antimicrobial activity of hybrid materials based on silver nanoparticles (AgNps) stabilized by polyvinylpyrrolidone (PVP)

Hybrid materials based on polyvinylpyrrolidone (PVP) with silver nanoparticles (AgNps) were synthesized applying two different strategies based on thermal or chemical reduction of silver ions to silver nanoparticles using PVP as a stabilizer. The formation of spherical silver nanoparticles with diameter ranging from 9 to 16 nm was confirmed by TEM analysis. UV-vis and FTIR spectroscopy were also applied to confirm the successful formation of AgNps. The antibacterial activity of the synthesized AgNPs/PVP against etalon strains of three different groups of bacteria—Staphylococcus aureus (S. aureus; gram-positive bacteria), Escherichia coli (E. coli; gram-negative bacteria), Pseudomonas aeruginosa (P. aeruginosa; non-ferment gram-negative bacteria), as well as against spores of Bacillus subtilis (B. subtilis) was studied. AgNps/PVP were tested for the presence of fungicidal activity against different yeasts and mold such as Candida albicans, Candida krusei, Candida tropicalis, Candida glabrata, and Aspergillus brasiliensis. The hybrid materials showed a strong antimicrobial effect against the tested bacterial and fungal strains and therefore have potential applications in biotechnology and biomedical science.     

Milk microbiome signatures of subclinical mastitis-affected cattle analysed by shotgun sequencing

Aims: Metagenomic analysis of milk samples collected from Kankrej, Gir (Bos indicus) and crossbred (Bos taurus × B. indicus) cattle harbouring subclinical mastitis was carried out by next‐generation sequencing 454 GS‐FLX technology to elucidate the microbial community structure of cattle milk. Methods and Results: Milk samples from Kankrej, Gir and crossbred cattle were subjected to metagenomic profiling by pyrosequencing. The Metagenomic analysis produced 63·07, 11·09 and 7·87 million base pairs (Mb) of sequence data, assembled in 264 798, 56 114 and 36 762 sequences with an average read length of 238, 197 and 214 nucleotides in Kankrej, Gir and crossbred cattle, respectively. Phylogenetic and metabolic profiles by the web‐based tool MG‐RAST revealed that the members of Enterobacteriales were predominant in mastitic milk followed by Pseudomonadales, Bacillales and Lactobacillales. Around 56 different species with varying abundance were detected in the subclinically infected milk. Escherichia coli was found to be the most predominant species in Kankrej and Gir cattle followed by Pseudomonas aeruginosa, Pseudomonas mendocina, Shigella flexneri and Bacillus cereus. In crossbred cattle, Staphylococcus aureus followed by Klebsiella pneumoniae, Staphylococcus epidermidis and E. coli were detected in descending order. Metabolic profiling indicated fluoroquinolones, methicillin, copper, cobalt–zinc–cadmium as the groups of antibiotics and toxic compounds to which the organisms showed resistance. Sequences indicating potential of organisms exhibiting multidrug resistance against antibiotics and resistance to toxic compounds were also present. Interestingly, presence of bacteriophages against Staph. aureus, E. coli, Enterobacter and Yersinia species was also observed. Conclusions: The analysis identified potential infectious organisms in mastitis, resistance of organisms to antibiotics and chemical compounds and the natural resistance potential of dairy cows. Significance and Impact of the Study: The findings of this study may help in formulating strategies for the prevention and treatment of mastitis in dairy animals and consequently in reducing economic losses incurred because of it.     

Antimicrobial activity of chemically and biologically synthesized silver nanoparticles against some fish pathogens

Pathogens isolated from fish appear to possess considerable antimicrobial resistance and represent a problem for the economy and public health. Natural antimicrobial substitutes to traditional antibiotics represent an essential tool in the fight against antibiotic resistance. Nanotechnology has shown considerable potential in different research fields, and the antimicrobial properties of silver nanoparticles are known. Silver has been used for medical purposes since ancient times because of its bactericidal properties, and the highly reactive surfaces of silver nanoparticles (AgNPs) indicate that they might have a function in antimicrobial applications. This work aimed to study the antimicrobial properties of biologically produced AgNPs from Origanum vulgare leaves compared to chemically produced AgNPs. Both types were characterized by UV–vis spectrophotometry, TEM, and dynamic light scattering and tested against three bacterial strains (Streptococcus agalactiae, and Aeromonas hydrophila, both isolated from Nile tilapia and Vibrio alginolyticus, isolated from sea bass) and three fungal strains (Aspergillus flavus, Fusarium moniliforme, and Candida albicans, all isolated from Nile tilapia). Disk diffusion test and evaluation of ultrastructure changes of tested microorganisms treated with AgNPs by transmission electron microscopy were performed. Moreover, the hemolytic properties of AgNPs were studied on chicken and goat red blood cells. The results obtained declare that the green biological production of silver nanoparticles is safer and more effective than the chemical one; moreover, AgNPs have interesting dose-dependent antimicrobial properties, with better results for biologically produced ones; their effectiveness against tested bacterial and fungal strains opens the way to their use to limit fish diseases, increase economy and improve human health.     

Antibacterial potential of hGlyrichin encoded by a human gene

Emerging multidrug‐resistant (MDR) bacteria are an enormous threat to human life because of their resistance to currently available antibiotics. The genes encoding antibacterial peptides have been studied extensively and are excellent candidates for a new generation of antibiotic drugs to fight MDR bacteria. In contrast to traditional antibiotics, antibacterial peptides, which do not cause drug resistance, have an unparalleled advantage. However, because most antibacterial peptides originate in species other than humans, the hetero‐immunological rejection of antibacterial peptides is a key disadvantage that limits their clinical application. In this study, we identify hGlyrichin as a potential human antibacterial polypeptide. The hGlyrichin polypeptide kills a variety of bacteria including the MDR bacteria methicillin‐resistant Staphylococcus aureus, MDR Pseudomonas aeruginosa, and MDR tubercle bacillus. A 19 amino acid peptide (pCM19) at positions 42–60 of hGlyrichin is crucial for its antibacterial activity. The hGlyrichin polypeptide kills bacteria through the destruction of the bacterial membrane. In addition, all peptides that are homologous to hGlyrichin have antibacterial activity and can penetrate the bacterial membrane. Importantly, hGlyrichin does not cause hemolytic side effects in vitro or in vivo. Therefore, based on the virtues of hGlyrichin, i.e., the absence of hetero‐immunological rejection and hemolytic side effects and the unambiguous efficacy of killing pathogenic MDR bacteria, we propose hGlyrichin as a potential human antibacterial polypeptide. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.