Synergistic and Additive Effects of Menadione in Combination with Antibiotics on Multidrug-Resistant Staphylococcus aureus: Insights from Structure-Function Analysis of Naphthoquinones.

Antimicrobial resistance (AMR) interferes with the effective treatment of infections and increases the risk of microbial spread and infection-related illness and death. The synergistic activities of combinations of antimicrobial compounds offer satisfactory approaches to some extent. Structurally diverse naphthoquinones (NQs) including menadione (-CH3 group at C2) exhibit substantial antimicrobial activities against multidrug-resistant (MDR) pathogens. We explored the combinations of menadione with antibiotic ciprofloxacin or ampicillin against Staphylococcus aureus and its biofilms. We found an additive (0.590 %) were also observed. However, preformed biofilms were not affected. Dent formation was also evident in S. aureus treated with the test compounds. The structure-function relationship (SFR) of NQs was used to determine and predict their activity pattern against pathogens. Analysis of 10 structurally distinct NQs revealed that the compounds with -Cl, -Br, -CH3 , or -OH groups displayed the lowest MICs (32-256 µg/mL). Furthermore, 1,4-NQs possessing a halogen or -CH3 moiety showed elevated ROS activity, whereas molecules with an -OH group affected cell integrity. Improved activity of antimicrobial combinations and SFR approaches are significant in antimicrobial therapies.

Production and characterization of bioemulsifier by Parapedobacter indicus.

The current study evaluated Parapedobacter indicus MCC 2546 for its potential to produce a bioemulsifier (BE). Screening methods performed for BE production by P. indicus MCC 2546 showed good lipase activity, positive drop collapse test, and oil-spreading activity. Furthermore, it showed maximum emulsification activity (225 EU/ml) and emulsification index (E24 50%) at 37°C in Luria Bertani broth at 72 h with olive oil as a substrate. The optimal pH and NaCl concentration for maximum emulsification activity were 7 and 1%, respectively. P. indicus MCC 2546 lowered the surface tension of the culture medium from 59.65 to 50.42 ± 0.78 mN/m. BE produced was composed of 70% protein and 30% carbohydrate, which showed the protein-polysaccharide nature of the BE. Furthermore, Fourier transform infrared spectroscopy analysis confirmed the same. P. indicus MCC 2546 showed a catecholate type of siderophore production. This is the first report on BE and siderophore production by the genus Parapedobacter.

Diversity of resistant determinants, virulence factors, and mobile genetic elements in Acinetobacter baumannii from India: A comprehensive in silico genome analysis.

Introduction: The frequency of infections associated with multidrug resistant A. baumannii has risen substantially in India. The use of next-generation sequencing (NGS) techniques combined with comparative genomics has great potential for tracking, monitoring, and ultimately controlling the spread of this troublesome pathogen. Here, we investigated the whole genome sequences of 47 A. baumannii from India. Methods: In brief, A. baumannii genomes were analyzed for the presence of antibiotic resistance genes (ARGs), virulence factors genes (VFGs), and mobile genetic elements (MGEs) using various in silico tools. The AbaR-type resistance islands (AbaRIs) were detected by examining the genetic environment of the chromosomal comM gene. Multilocus sequence types were determined using the Pasteur scheme. The eBURST and whole genome SNPs-based phylogenetic analysis were performed to analyze genetic diversity between A. baumannii genomes. Results and discussion: A larger number of A. baumannii isolates belonging to the ST2 genotype was observed. The SNPs-based phylogenetic analysis showed a diversity between compared genomes. The predicted resistome showed the presence of intrinsic and acquired ARGs. The presence of plasmids, insertion sequences, and resistance islands carrying putative ARGs conferring resistance to antibiotics, quaternary ammonium compounds, and heavy metals was predicted in 43 (91%) genomes. The presence of putative VFGs related to adherence, biofilm formation and iron uptake was observed in the study. Overall, the comprehensive genome analysis in this study provides an essential insight into the resistome, virulome and mobilome of A. baumannii isolates from India.

Characterization of Novel Klebsiella Phage PG14 and Its Antibiofilm Efficacy.

The increasing frequency of infections caused by multidrug-resistant Klebsiella pneumoniae demands the development of unconventional therapies. Here, we isolated, characterized, and sequenced a Klebsiella phage PG14 that infects and lyses carbapenem-resistant K. pneumoniae G14. Phage PG14 showed morphology similar to the phages belonging to the family Siphoviridae. The adsorption curve of phage PG14 showed more than 90% adsorption of phages on a host within 12 min. A latent period of 20 min and a burst size of 47 was observed in the one step growth curve. Phage PG14 is stable at a temperature below 30°C and in the pH range of 6 to 8. The PG14 genome showed no putative genes associated with virulence and antibiotic resistance. Additionally, it has shown lysis against 6 out of 13 isolates tested, suggesting the suitability of this phage for therapeutic applications. Phage PG14 showed more than a 7-log cycle reduction in K. pneumoniae planktonic cells after 24 h of treatment at a multiplicity of infection (MOI) of 10. The phage PG14 showed a significant inhibition and disruption of biofilm produced by K. pneumoniae G14. The promising results of this study nominate phage PG14 as a potential candidate for phage therapy. IMPORTANCE Klebsiella pneumoniae is one of the members of the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) group of pathogens and is responsible for nosocomial infections. The global increase of carbapenem-resistant K. pneumoniae has developed a substantial clinical threat because of the dearth of therapeutic choices available. K. pneumoniae is one of the commonly found bacteria responsible for biofilm-related infections. Due to the inherent tolerance of biofilms to antibiotics, there is a growing need to develop alternative strategies to control biofilm-associated infections. This study characterized a novel bacteriophage PG14, which can inhibit and disrupt the K. pneumoniae biofilm. The genome of phage PG14 does not show any putative genes related to antimicrobial resistance or virulence, making it a potential candidate for phage therapy. This study displays the possibility of treating infections caused by multidrug-resistant (MDR) isolates of K. pneumoniae using phage PG14 alone or combined with other therapeutic agents.

Synergistic and antibiofilm potential of Curcuma aromatica derived silver nanoparticles in combination with antibiotics against multidrug-resistant pathogens.

Hospital acquired infections caused due to ESKAPE pathogens pose a challenge for treatment due to their growing antimicrobial resistance. Curcuma aromatica (CA) is traditionally known for its antibacterial, wound healing and anti-inflammatory properties. The present study highlights the biogenic synthesis of silver nanoparticles (CAAgNPs) capped and stabilized by the compounds from CA rhizome extract, also further demonstrating their antibacterial, antibiofilm and synergistic effects against multidrug-resistant (MDR) pathogens. CAAgNPs were synthesized using aqueous rhizome extract of CA (5 mg/ml) and AgNO3 (0.8 mM) incubated at 60°C up to 144 h. UV-vis spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) revealed CAAgNPs with characteristic peak at 430 nm, 13 ± 5 nm size of spherical shape, showing presence of silver and crystalline nature, respectively. Dynamic light scattering (DLS) and zeta potential confirmed their monodispersed nature with average diameter of 77.88 ± 48.60 nm and stability. Fourier transform infrared spectroscopic (FTIR) analysis demonstrated the presence of phenolic -OH and carbonyl groups possibly involved in the reduction and stabilization of CAAgNPs. The minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs) and minimum biofilm inhibitory concentrations (MBICs) of CAAgNPs against Pseudomonas aeruginosa, NCIM 5029 and PAW1, and, Staphylococcus aureus, NCIM 5021 and S8 were in range from 8 to 128 µg/ml. Almost 50% disruption of pre-formed biofilms at concentrations 8-1,024 µg/ml was observed. Fluorescence microscopy and FESEM analysis confirmed cell death and disruption of pre-formed biofilms of P. aeruginosa PAW1 and S. aureus S8. Checkerboard assay demonstrated the synergistic effect of CAAgNPs (0.125-4 µg/ml) in combination with various antibiotics (0.063-1,024 µg/ml) against planktonic and biofilm forms of P. aeruginosa PAW1. The study confirms the antibacterial and antibiofilm activity of CAAgNPs alone and in combination with antibiotics against MDR pathogens, thus, reducing the dose as well as toxicity of both. CAAgNPs have the potential to be used in wound dressings and ointments, and to improve the performances of medical devices and surgical implants. In vivo toxicity of CAAgNPs however needs to be tested further using mice models.

Antibacterial and Antibiofilm Potency of Menadione Against Multidrug-Resistant S. aureus.

Menadione is an analogue of 1,4-naphthoquinone (1,4-NQ) that possesses enormous pharmaceutical potential. The minimum inhibitory concentration (MIC) of menadione was determined against eighteen pathogens of the ESKAPE category, including thirteen multidrug-resistant (MDR) and five standard strains. From a total of eighteen pathogens, five strains of S. aureus (four: MDR and one: Standard strain) were considered further for detailed studies. This study included the determination of minimum bactericidal concentration (MBC), time-kill assay, scanning electron microscopic technique (SEM), and detection of reactive oxygen species (ROS). Additionally, the effect of menadione on biofilms of three strains of S. aureus was performed through crystal violet assay, SEM, and confocal laser scanning microscopy (CLSM). Menadione exerted substantial antibacterial activity against S. aureus (S8, S9, NCIM 5021) at a lower MIC (64 µg/mL). Whereas, the MIC of 256 µg/mL was displayed against J2 and J4 (MDR and biofilm-forming strains). The time-killing effect of menadione against S. aureus strains was observed after 9 h at MBCs of 64 µg/mL (NCIM 5021), 128 µg/mL (S8, S9), and 512 µg/mL (J2, J4). Enhanced levels of ROS in all five S. aureus were observed in presence of menadione (MICs and MBCs). The relation of enhanced ROS due to menadione activity invigorated us to explore its effect on S. aureus biofilms. We report menadione-mediated inhibition (> 90%) of biofilm formation (at respective MICs) and effect on preformed biofilms (> 85%) at 1024 µg/mL. Menadione possessing antibacterial and antibiofilm potentials are imperative in the era of multidrug resistance developed by bacterial pathogens.

Synergistic effect of antibiotic combinations on Staphylococcus aureus biofilms and their persister cell populations.

Treatment of staphylococcal infections is difficult due to multidrug resistance with their persister forms posing an added threat of recalcitrant infections. Antibiotic combinations are widely studied as an alternative strategy to combat them; therefore, they merit further investigation into their effect on the number of persister cells. In the present study, the fractional inhibitory concentrations of antibiotic combinations ciprofloxacin-daptomycin, ciprofloxacin-vancomycin, daptomycin-tobramycin, and tobramycin-vancomycin (checkerboard assay) were determined against two previously studied clinical (S48 and J6) and one standard (NCIM 5021) isolate of Staphylococcus aureus. They showed synergistic effects with a 2 to 256-fold reduction in MICs. All combinations also resulted in inhibition and disruption of biofilms in a concentration-dependent manner. All antibiotic combinations, except ciprofloxacin-daptomycin, showed total biofilm inhibition at 100X MICs. Similarly, antibiotic combination at 100X MIC showed 77-97% disruption of preformed biofilms. Time-kill assays performed at a 100X MIC combination against stationary-phase cells showed a two to six log10 reduction in CFU followed by a plateau indicating the presence of persisters. Significant differences were observed in persister cell fraction remaining after treatment with antibiotic combinations compared to monotherapies (p < 0.05) and therefore merit further investigation in clinical use for treatment against persisters.

Corrigendum: Diversity of resistant determinants, virulence factors, and mobile genetic elements in Acinetobacter baumannii from India: A comprehensive in silico genome analysis.

[This corrects the article DOI: 10.3389/fcimb.2022.997897.].

Bacteriogenic Platinum Nanoparticles for Application in Nanomedicine.

Nanoscale materials have recently gained wide attention due to their potential to revolutionize many technologies and industrial sectors, including information technology, homeland security, transportation, energy, food safety, environmental science, catalysis, photonics and medicine. Among various nanoparticles, platinum nanoparticles (PtNPs) are widely used for biomedical applications, including imaging, implants, photothermal therapy and drug delivery. Indeed, PtNPs possesses intrinsic antimicrobial, antioxidant, and anticancer properties. Also, due to their remarkable catalytic activity, they are able to reduce the intracellular reactive oxygen species (ROS) levels and impair the downstream pathways leading to inflammation. Various approaches, including both physical and chemical methods, are currently employed for synthesis of PtNPs. However, the use of hazardous reaction conditions and toxic chemicals in these processes poses a potential threat to the environment and severely compromise the biocompatibility of the nanoparticles. Hereby, increasing need for exploitation of novel routes for synthesis of PtNPs has led to development of biological fabrication using microbes, specifically bacteria. Herein, we present a most comprehensive report on biogenesis of PtNPs by several bacteria like Acinetobacter calcoaceticus, Desulfovibrio alaskensis, Escherichia coli, Shewanella algae, Plectonema boryanum, etc. An overview of the underlying mechanisms of both enzymatic and non-enzymatic methods of synthesis is included. Moreover, this review highlights the scope of developing optimized process to control the physicochemical properties, such as the nanoparticle surface chemistry, charge, size and shape, which, in turn, may affect their nanotoxicity and response at the biointerface for nanomedicine applications.

Antibiofilm and antipersister activity of acetic acid against extensively drug resistant Pseudomonas aeruginosa PAW1.

Pseudomonas aeruginosa is an ESKAPE pathogen associated with difficult-to-treat burn wound and surgical-site infections. This study aimed to characterise an extensively drug resistant (XDR) P. aeruginosa isolate (designated PAW1) and to investigate the antibiofilm and antipersister effect of acetic acid on PAW1. PAW1 was identified using biotypic (VITEK) and genotypic (16S rDNA) analysis. Minimum inhibitory concentration (MIC) and disc susceptibility testing showed high level resistance against all antibiotics from classes including beta lactams, cephems, carbapenems and fluoroquinolones. It was therefore identified as extensively drug resistant (XDR), showing resistance to all antibiotics except for, aminoglycoside (gentamicin and netilmicin) and lipopeptides (polymyxin B). Time kill assays showed antibiotic tolerant, persister cell formation in presence of 100X MICs of gentamicin and polymyxin B. Other virulence traits such as ability to produce lipase, protease, haemolysin, and siderophores and to form biofilms were additional factors which may contribute to its pathogenicity. PAW1 showed promising susceptibility against acetic acid with MIC and minimum biofilm inhibitory concentration of 0.156% (v/v). Percent viability of PAW1 was dependent on dose and treatment time of acetic acid. 0.625% acetic acid treatment of 5 minutes was effective in killing >90% planktonic cells showing lesser toxicity to L929 cells (IC50 = 0.625%). Biofilm disruption caused due to acetic acid was also dose dependent, showing 40.57% disruption after treatment with 0.625% acetic acid for 5 minutes. FESEM imaging and live dead staining of planktonic and biofilm forms of PAW1 confirmed that acetic acid treatment caused 19.04% of cell shrinkage and disruption of extracellular matrix resulting in killing of cells. Antipersister activity of acetic acid was demonstrated by showing complete killing of PAW1 at 4X MIC. Overall, this study characterised an XDR isolate P. aeruginosa showing resistance and tolerance to various antibiotics. Antipersister and antibiofilm effect of acetic acid demonstrates the importance of forgotten topical agents as an effective strategy to treat XDR pathogens.

Antibiotic Tolerance in Biofilm and Stationary-Phase Planktonic Cells of Staphylococcus aureus.

The ability of Staphylococcus aureus to form biofilms and persisters is a major cause of recalcitrant infections that are difficult to treat. We have examined time-dependent variation in persister population present in stationary-phase planktonic cells and biofilms of S. aureus when treated with bactericidal antibiotics having different cellular targets. Fourteen isolates identified as S. aureus were found to be resistant to three to nine classes of antibiotics tested according to the CLSI guidelines. Among the sensitive isolates, S48 was found to be the strongest biofilm producer, whereas J6 was the weakest. The four antibiotics, ciprofloxacin, daptomycin, tobramycin, and vancomycin, inhibited biofilm formation, whereas daptomycin was the strongest in disrupting 24-hr-old biofilm. Treatment of stationary-phase planktonic cells with 100 × minimum inhibitory concentration (MIC) of these antibiotics showed a typical biphasic pattern indicating the presence of persister cells. Twenty-four-hour-old biofilm of the two isolates tested at 100 × MIC of the antibiotics showed a similar biphasic pattern. Tolerance of biofilm cells was greater as compared with planktonic cells, which could be due to elevated number of persisters found in the biofilm as compared with planktonic cells.

Anticancer potential of AgNPs synthesized using Acinetobacter sp. and Curcuma aromatica against HeLa cell lines: A comparative study.

BACKGROUND: Biogenic nanoparticles are gaining attention due to their low toxicity and numerous biomedical applications. Present study aimed to compare the potential anticancer activity of two biogenic silver nanoparticles (bAgNPs and pAgNPs) against human cervical cancer cell lines (HeLa). METHODS: bAgNPs were synthesized using Acinetobacter sp. whereas pAgNPs were synthesized using aqueous root extract of Curcuma aromatica. Effect of these nanoparticles on HeLa cells viability was studied using MTT assay and colony formation assay. Anticancer potential was determined using fluorescence microscopy and flow cytometry studies. Bio-compatibility studies were performed against peripheral blood mononuclear cells (PBMCs). RESULTS: Both the nanoparticles showed 50 % viability of peripheral blood mononuclear cells (PBMCs) when used at high concentration (200 µg/mL). IC50 for bAgNPs and pAgNPs against HeLa cells were 17.4 and 14 µg/mL respectively. Colony formation ability of Hela cells was reduced on treatment with both nanoparticles. Acridine orange and ethidium bromide staining demonstrated that bAgNPs were cytostatic whereas pAgNPs were apoptotic. JC-1 dye staining revealed that the mitochondrial membrane potential was affected on treatment with pAgNPs while it remained unchanged on bAgNPs treatment. Flow cytometry confirmed cell cycle arrest in HeLa cells on treatment with nanoparticles further leading to apoptosis in case of pAgNPs. About 77 and 58 % HeLa cells were found in subG1 phase on treatment with bAgNPs and pAgNPs respectively. bAgNPs showed cytostatic effect on HeLa cells arresting the cell growth in subG1 phase, whereas, pAgNPs triggered death of HeLa cells through mitochondrial membrane potential impairment and apoptosis. CONCLUSION: Overall, bAgNPs and pAgNPs could be safe and showed potential to be used as anticancer nano-antibiotics against human cervical cancer cells.

Bioimaging Applications of Carbon dots (C. dots) and its Cystamine Functionalization for the Sensitive Detection of Cr(VI) in Aqueous Samples.

In this study, one step hydrothermal synthetic strategy was adopted for preparing carbon dots (C. dots) from jeera (Cumin: Cuminum cyminum), a naturally abundant and cost effective carbon source. The physical, optical and surface functional properties of C. dots were extensively studied by different techniques such as Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), spectrophotometry, fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The obtained C. dots were highly water dispersible and photostable with a quantum yield of 5.33%. The antioxidant property of C. dots was investigated by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay. The C. dots were then capped with cystamine using 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide (EDC) and N-Hydroxysuccinimide (NHS) coupling chemistry to design a selective sensing system for chromium (VI) (Cr (VI)). The minimum detection limit of Cr (VI) was found to be 1.57 µM. Biocompatibility and low toxicity of C. dots obtained from jeera made it a potential tool for bioimaging application. The internalisation of C. dots by MCF-7 breast cancer cells and Multi Drug Resistant (MDR) pathogens such as Staphylococcus aureus and Pseudomonas aeruginosa were proved by the bioimaging of respective cells.

Emerging Strategies to Combat ESKAPE Pathogens in the Era of Antimicrobial Resistance: A Review.

The acronym ESKAPE includes six nosocomial pathogens that exhibit multidrug resistance and virulence: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. Persistent use of antibiotics has provoked the emergence of multidrug resistant (MDR) and extensively drug resistant (XDR) bacteria, which render even the most effective drugs ineffective. Extended spectrum ß-lactamase (ESBL) and carbapenemase producing Gram negative bacteria have emerged as an important therapeutic challenge. Development of novel therapeutics to treat drug resistant infections, especially those caused by ESKAPE pathogens is the need of the hour. Alternative therapies such as use of antibiotics in combination or with adjuvants, bacteriophages, antimicrobial peptides, nanoparticles, and photodynamic light therapy are widely reported. Many reviews published till date describe these therapies with respect to the various agents used, their dosage details and mechanism of action against MDR pathogens but very few have focused specifically on ESKAPE. The objective of this review is to describe the alternative therapies reported to treat ESKAPE infections, their advantages and limitations, potential application in vivo, and status in clinical trials. The review further highlights the importance of a combinatorial approach, wherein two or more therapies are used in combination in order to overcome their individual limitations, additional studies on which are warranted, before translating them into clinical practice. These advances could possibly give an alternate solution or extend the lifetime of current antimicrobials.

Molecular characterization of outer membrane vesicles released from Acinetobacter radioresistens and their potential roles in pathogenesis.

Acinetobacter radioresistens is an important member of genus Acinetobacter from a clinical point of view. In the present study, we report that a clinical isolate of A. radioresistens releases outer membrane vesicles (OMVs) under in vitro growth conditions. OMVs were released in distinctive size ranges with diameters from 10 to 150 nm as measured by the dynamic light scattering (DLS) technique. Additionally, proteins associated with or present into OMVs were identified using LC-ESI-MS/MS. A total of 71 proteins derived from cytosolic, cell membrane, periplasmic space, outer membrane (OM), extracellular and undetermined locations were found in OMVs. The initial characterization of the OMV proteome revealed a correlation of some proteins to biofilm, quorum sensing, oxidative stress tolerance, and cytotoxicity functions. Thus, the OMVs of A. radioresistens are suggested to play a role in biofilm augmentation and virulence possibly by inducing apoptosis.

Time dependent enhanced resistance against antibiotics & metal salts by planktonic & biofilm form of Acinetobacter haemolyticus MMC 8 clinical isolate.

BACKGROUND & OBJECTIVES: Available literature shows paucity of reports describing antibiotic and metal resistance profile of biofilm forming clinical isolates of Acinetobacter haemolyticus. The present study was undertaken to evaluate the antibiotic and metal resistance profile of Indian clinical isolate of A. haemolyticus MMC 8 isolated from human pus sample in planktonic and biofilm form. METHODS: Antibiotic susceptibility and minimum inhibitory concentration were determined employing broth and agar dilution techniques. Biofilm formation was evaluated quantitatively by microtiter plate method and variation in complex architecture was determined by scanning electron microscopy. Minimum biofilm inhibiting concentration was checked by Calgary biofilm device. RESULTS: Planktonic A. haemolyticus MMC 8 was sensitive to 14 antibiotics, AgNO 3 and HgC1 2 resistant to streptomycin and intermediately resistant to netilmycin and kanamycin. MMC 8 exhibited temporal variation in amount and structure of biofilm. There was 32-4000 and 4-256 fold increase in antibiotic and metal salt concentration, respectively to inhibit biofilm over a period of 72 h as against susceptible planktonic counterparts. Total viable count in the range of 10(5)-10(6) cfu / ml was observed on plating minimum biofilm inhibiting concentration on Muller-Hinton Agar plate without antimicrobial agents. Biofilm forming cells were several folds more resistant to antibiotics and metal salts in comparison to planktonic cells. Presence of unaffected residual cell population indicated presence of persister cells. INTERPRETATION & CONCLUSIONS: The results indicate that biofilm formation causes enhanced resistance against antibiotics and metal salts in otherwise susceptible planktonic A. haemolyticus MMC 8.

Phytochemical analysis and free radical scavenging activity of medicinal plants Gnidia glauca and Dioscorea bulbifera.

Gnidia glauca and Dioscorea bulbifera are traditional medicinal plants that can be considered as sources of natural antioxidants. Herein we report the phytochemical analysis and free radical scavenging activity of their sequential extracts. Phenolic and flavonoid content were determined. Scavenging activity was checked against pulse radiolysis generated ABTS(•+) and OH radical, in addition to DPPH, superoxide and hydroxyl radicals by biochemical methods followed by principal component analysis. G. glauca leaf extracts were rich in phenolic and flavonoid content. Ethyl acetate extract of D. bulbifera bulbs and methanol extract of G. glauca stem exhibited excellent scavenging of pulse radiolysis generated ABTS(•+) radical with a second order rate constant of 2.33 × 10(6) and 1.72 × 10(6), respectively. Similarly, methanol extract of G. glauca flower and ethyl acetate extract of D. bulbifera bulb with second order rate constants of 4.48 × 10(6) and 4.46 × 10(6) were found to be potent scavengers of pulse radiolysis generated OH radical. G. glauca leaf and stem showed excellent reducing activity and free radical scavenging activity. HPTLC fingerprinting, carried out in mobile phase, chloroform: toluene: ethanol (4: 4: 1, v/v) showed presence of florescent compound at 366 nm as well as UV active compound at 254 nm. GC-TOF-MS analysis revealed the predominance of diphenyl sulfone as major compound in G. glauca. Significant levels of n-hexadecanoic acid and octadecanoic acid were also present. Diosgenin (C27H42O3) and diosgenin (3á,25R) acetate were present as major phytoconstituents in the extracts of D. bulbifera. G. glauca and D. bulbifera contain significant amounts of phytochemicals with antioxidative properties that can be exploited as a potential source for herbal remedy for oxidative stress induced diseases. These results rationalize further investigation in the potential discovery of new natural bioactive principles from these two important medicinal plants.

Gnidia glauca flower extract mediated synthesis of gold nanoparticles and evaluation of its chemocatalytic potential.

BACKGROUND: Novel approaches for synthesis of gold nanoparticles (AuNPs) are of utmost importance owing to its immense applications in diverse fields including catalysis, optics, medical diagnostics and therapeutics. We report on synthesis of AuNPs using Gnidia glauca flower extract (GGFE), its detailed characterization and evaluation of its chemocatalytic potential. RESULTS: Synthesis of AuNPs using GGFE was monitored by UV-Vis spectroscopy and was found to be rapid that completed within 20 min. The concentration of chloroauric acid and temperature was optimized to be 0.7 mM and 50°C respectively. Bioreduced nanoparticles varied in morphology from nanotriangles to nanohexagons majority being spherical. AuNPs were characterized employing transmission electron microscopy, high resolution transmission electron microscopy. Confirmation of elemental gold was carried out by elemental mapping in scanning transmission electron microscopic mode, energy dispersive spectroscopy and X-ray diffraction studies. Spherical particles of size ~10 nm were found in majority. However, particles of larger dimensions were in range between 50-150 nm. The bioreduced AuNPs exhibited remarkable catalytic properties in a reduction reaction of 4-nitrophenol to 4-aminophenol by NaBH4 in aqueous phase. CONCLUSION: The elaborate experimental evidences support that GGFE can provide an environmentally benign rapid route for synthesis of AuNPs that can be applied for various purposes. Biogenic AuNPs synthesized using GGFE exhibited excellent chemocatalytic potential.

Characterization of eDNA from the clinical strain Acinetobacter baumannii AIIMS 7 and its role in biofilm formation.

Release of extracellular DNA (eDNA) was observed during in vitro growth of a clinical strain of Acinetobacter baumannii. Membrane vesicles (MV) of varying diameter (20-200 nm) containing DNA were found to be released by transmission electron microscopy (TEM) and atomic force microscopy (AFM). An assessment of the characteristics of the eDNA with respect to size, digestion pattern by DNase I/restriction enzymes, and PCR-sequencing, indicates a high similarity with genomic DNA. Role of eDNA in static biofilm formed on polystyrene surface was evaluated by biofilm augmentation assay using eDNA available in different preparations, for example, whole cell lysate, cell-free supernatant, MV suspension, and purified eDNA. Biofilm augmentation was seen up to 224.64%, whereas biofilm inhibition was 59.41% after DNase I treatment: confirming that eDNA facilitates biofilm formation in A. baumannii. This is the first paper elucidating the characteristics and role of eDNA in A. baumannii biofilm, which may provide new insights into its pathogenesis.