Antibacterial and antibiofilm activity of Abroma augusta stabilized silver (Ag) nanoparticles against drug-resistant clinical pathogens.

Infectious diseases remain among the most pressing concerns for human health. This issue has grown even more complex with the emergence of multidrug-resistant (MDR) bacteria. To address bacterial infections, nanoparticles have emerged as a promising avenue, offering the potential to target bacteria at multiple levels and effectively eliminate them. In this study, silver nanoparticles (AA-AgNPs) were synthesized using the leaf extract of a medicinal plant, Abroma augusta. The synthesis method is straightforward, safe, cost-effective, and environment friendly, utilizing the leaf extract of this Ayurvedic herb. The UV-vis absorbance peak at 424 nm indicated the formation of AA-AgNPs, with the involvement of numerous functional groups in the synthesis and stabilization of the particles. AA-AgNPs exhibited robust antibacterial and antibiofilm activities against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE). The MIC values of AA-AgNPs ranged from 8 to 32 µg/mL. Electron microscopic examination of the interaction of AA-AgNPs with the test bacterial pathogens showed a deleterious impact on bacterial morphology, resulting from membrane rupture and leakage of intracellular components. AA-AgNPs also demonstrated a dose-dependent effect in curtailing biofilm formation below inhibitory doses. Overall, this study highlights the potential of AA-AgNPs in the successful inhibition of both the growth and biofilms of MRSA and VRE bacteria. Following studies on toxicity and dose optimization, such AgNPs could be developed into effective medical remedies against infections.

Green Synthesis of Copper Oxide Nanoparticles from the Leaves of Aegle marmelos and Their Antimicrobial Activity and Photocatalytic Activities.

The leaves of the Aegle marmelos plant were used for the green synthesis of copper oxide nanoparticles and further characterized by different techniques, including (Ultra Violet-Visible) UV-Vis, Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX), Transmission electron microscopy (TEM) and X-ray diffraction (XRD). The UV-Vis showed a peak at 330 nm, which may be due to the Surface Plasmon Resonance phenomenon. XRD analysis showed the crystalline nature of copper oxide nanoparticles (CuO NPs). In contrast, SEM showed that nanoparticles were not aggregated or clumped, EDX showed the presence of elemental copper., and further, the TEM analysis revealed the average particle size of copper oxide nanoparticles to be 32 nm. The Minimum Inhibitory Concentration (MIC) for Escherichia coli (E. coli) and Staphylococcusaureus (S. aureus) was found to be 400 µg/mL, whereas for Candida albicans (C. albicans) and Candida dubliniensis (C. dubliniensis) it was 800 µg/mL. The zone of inhibition in the well diffusion assay showed the antimicrobial activity of copper oxide nanoparticles, and it also showed that as the concentration of copper oxide nanoparticles increased, the zone of inhibition also increased. Further, the electron microscopic view of the interaction between copper oxide nanoparticles and C. albicans cells showed that CuO NPs were internalized and attached to the cell membrane, which caused changes in the cellular structure and caused deformities which eventually led to cell death. The prepared CuO NPs showed significant photocatalytic degradation of organic dyes in the presence of sunlight.

Biosynthesis of Gold Nanoparticles and Its Effect against Pseudomonas aeruginosa.

Antimicrobial resistance has posed a serious health concern worldwide, which is mainly due to the excessive use of antibiotics. In this study, gold nanoparticles synthesized from the plant Tinospora cordifolia were used against multidrug-resistant Pseudomonas aeruginosa. The active components involved in the reduction and stabilization of gold nanoparticles were revealed by gas chromatography-mass spectrophotometry(GC-MS) of the stem extract of Tinospora cordifolia. Gold nanoparticles (TG-AuNPs) were effective against P. aeruginosa at different concentrations (50,100, and 150 µg/mL). TG-AuNPs effectively reduced the pyocyanin level by 63.1% in PAO1 and by 68.7% in clinical isolates at 150 µg/mL; similarly, swarming and swimming motilities decreased by 53.1% and 53.8% for PAO1 and 66.6% and 52.8% in clinical isolates, respectively. Biofilm production was also reduced, and at a maximum concentration of 150 µg/mL of TG-AuNPs a 59.09% reduction inPAO1 and 64.7% reduction in clinical isolates were observed. Lower concentrations of TG-AuNPs (100 and 50 µg/mL) also reduced the pyocyanin, biofilm, swarming, and swimming. Phenotypically, the downregulation of exopolysaccharide secretion from P. aeruginosa due to TG-AuNPs was observed on Congo red agar plates.

Green Synthesis of Silver Nanoparticles from Camellia sinensis and Its Antimicrobial and Antibiofilm Effect against Clinical Isolates.

The green synthesis method of was used for the synthesis of silver nanoparticles using Camellia sinensis (green tea). The Camellia sinensis silver nanoparticles (CS-AgNPs) were characterized using different techniques, including UV-Vis (ultra violet-visible), SEM (scanning electron microscopy), TEM (transmission electron microscopy), and XRD (X-ray diffraction). The average size of the CS-AgNPs was 52 nm, according to TEM. The CS-AgNPs showed excellent antibacterial and antifungal activity. The MIC (minimum inhibitory concentration) against bacterial isolates varied from 31.25 to 62.5 µg/mL, whereas for fungal isolates, the MIC varied from 125 to 250 µg/mL. The presence of a zone in the well diffusion assay showed the antimicrobial nature of CS-AgNPs. Further, CLSM (confocal laser scanning microscopy) showed that CS-AgNPs possess antibiofilm activity. The interaction of CS-AgNPs with the Candidal cells was analyzed using TEM, and it was revealed that CS-AgNPs entered the cell and disrupted the cell machinery.

Circulation of oxytetracycline- and ciprofloxacin-resistant commensal Escherichia coli strains in broiler chickens and farm environments, Bangladesh.

BACKGROUND AND AIM: The emergence of antimicrobial resistance (AMR) in commensal organism, such as Escherichia coli of food animals, is an alarming issue for global health. It increases the possibility of transmitting AMR determinant(s) to human bacterial pathogens by transferable genetic materials, particularly by plasmids. Hence, it is important to know which resistant genes are being carried by commensal organisms in food chain in a country and their level of temporal loads. As a result, pre-emptive measures can be advocated with an aim to reduce their risks in their primary source of circulation which consequently would benefit the public health. MATERIALS AND METHODS: Commensal E. coli strains from broiler chickens on randomly selected 30 farms and the farm environments were examined for the frequencies of isolation of resistant strains to oxytetracycline and ciprofloxacin. Five birds were randomly selected from each farm to collect cloacal swab samples (total of 150 samples). Furthermore, a total of 150 environmental samples comprising one each from feed, water, soil, litter, and litter damping site of each farm were screened for the isolation of commensal E. coli strains. Strains thus obtained were initially tested for their resistance to oxytetracycline and ciprofloxacin by Kirby-Bauer disk diffusion method. Oxytetracycline-resistant strains were further screened for the presence of resistance determining genes, namely, tetA, tetB, and tetC by uniplex polymerase chain reactions. Risks associated with the isolation frequency of oxytetracycline- and ciprofloxacin-resistant E. coli were also assessed by univariable logistic regression analysis. RESULTS: The results revealed that all E. coli isolates, regardless of the source of origin, were resistant to oxytetracycline, while 78.4% (95% confidence interval [CI] 69.1-85.5%) showed resistance to ciprofloxacin. All the randomly selected (20) oxytetracycline-resistant strains harbored the tetA gene, whereas tetB and tetC were reported in three and two isolates, respectively. After univariable analysis, only one variable, that is, strain 1 of broiler chickens compared to two other strains was found to be positively associated with the isolation of ciprofloxacin-resistant E. coli (odds ratio 12.75 [95% CI 1.0-157.1], p=0.047). CONCLUSION: Resistance emerged against oxytetracycline and ciprofloxacin in commensal E. coli strains circulating in live poultry and farm environments in Bangladesh seems to be very high. Thus, human infection with drug-resistant E. coli strains through food chain will critically compromise the therapeutic measures currently available.

An assessment on potential risk pathways for the incursion of highly pathogenic avian influenza virus in backyard poultry farm in Bangladesh.

BACKGROUND AND AIM: Highly pathogenic avian influenza (HPAI) is a deadly virus of zoonotic potential. The study mainly aims to determine the risk pathways (RPs) for the probable incursion of HPAI virus (HPAIV) in backyard poultry in Bangladesh. MATERIALS AND METHODS: The study involves expert elicitation technique. The concept map determines the possible RPs. The map consists of 16 concepts, each with nodes from which probabilities of an event originates. These probabilities are described by qualitative descriptors ranging from negligible to high. Risk assessment has been performed using the subjective risk assessment tool. RESULTS: The tool demonstrates positive correlation among groups of experts in the level of agreement by scoring RP; however, the level of agreement varies from 71% to 93% among group of experts. The median risk score of viral incursion through the "Exposure of backyard poultry with farm poultry in the trading market" was 11 and ranked as top, followed by "Contaminated live bird market environment" and "Sharing common scavenging space with migratory birds" (median risk score, 10.5; rank, 2), and "Scavenging of infected slaughtered poultry remnants by backyard poultry" (median risk score, 5.3; rank, 3) when no control options were applied along with the RPs. After applying or considering control option along with contaminated live bird market environment, the median risk score was reduced to 5.0. Applying a specific control option along with each RP reduced estimated median risk scores for HPAIV incursions. CONCLUSION: This study provides an insight into the incursion risks of HPAIV through various RPs in backyard poultry in Bangladesh.

Effect of Biosynthesized ZnO Nanoparticles on Multi-Drug Resistant Pseudomonas Aeruginosa.

Synthesis of nanoparticles using the plants has several advantages over other methods due to the environmentally friendly nature of plants. Besides being environmentally friendly, the synthesis of nanoparticles using plants or parts of the plants is also cost effective. The present study focuses on the biosynthesis of zinc oxide nanoparticles (ZnO NPs) using the seed extract of Butea monsoperma and their effect on to the quorum-mediated virulence factors of multidrug-resistant clinical isolates of Pseudomonas aeruginosa at sub minimum inhibitory concentration (MIC). The synthesized ZnO NPs were characterized by different techniques, such as Fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and transmission electron microscopy (TEM). The average size of the nanoparticles was 25 nm as analyzed by TEM. ZnO NPs at sub MIC decreased the production of virulence factors such as pyocyanin, protease and hemolysin for P. aeruginosa (p ≤ 0.05). The interaction of NPs with the P. aeruginosa cells on increasing concentration of NPs at sub MIC levels showed greater accumulation of nanoparticles inside the cells as analyzed by TEM.

Acquisition of Plasmid-Mediated Colistin Resistance Gene mcr-1 in Escherichia coli of Livestock Origin in Bangladesh.

Aims: To investigate plasmid-borne colistin resistance mechanism (plasmid-mediated colistin resistance [mcr-1]) in Escherichia coli of human, veterinary, and environmental origin in Bangladesh. Materials and methods: A total of 810 samples were collected from different sources. Isolation and identification of E. coli was performed using classical bacteriology and then tested for antimicrobial susceptibility. Colistin-resistant isolates were further analyzed for mcr-1 gene using PCR. Minimum inhibitory concentration (MIC) was determined using microbroth dilution technique. After sequencing of mcr-1 gene, phylogenetics was conducted to see the relationship with other mcr-1 gene sequences. Results: A total of 358 E. coli were isolated from 810 samples of humans, animals, environment, and food in Bangladesh. Of them 49 (15.9%) isolates were phenotypically resistant to colistin and 254 (70.9%) were resistant to multiple antimicrobials. mcr-1 gene was detected in three E. coli isolates of poultry source. For the three mcr-1 positive isolates the MIC of colistin sulfate was 4, 8, and 128 µg/mL. Gene sequencing of two of the three mcr-1 positive isolates and phylogenetic analysis showed close similarities of one isolate to other mcr-1 sequences available at GenBank while the other appeared to have evolved locally. Conclusion: First-ever report on circulation of mcr-1 E. coli of livestock origin in Bangladesh.

Biogenic Gold Nanoparticles as Potent Antibacterial and Antibiofilm Nano-Antibiotics against Pseudomonas aeruginosa.

Abstract: Plant-based synthesis of eco-friendly nanoparticles has widespread applications in many fields, including medicine. Biofilm-a shield for pathogenic microorganisms-once formed, is difficult to destroy with antibiotics, making the pathogen resistant. Here, we synthesized gold nanoparticles (AuNPs) using the stem of an Ayurvedic medicinal plant, Tinospora cordifolia, and studied the action of AuNPs against Pseudomonas aeruginosa PAO1 biofilm. The synthesized AuNPs were characterized by techniques such as ultraviolet-visible spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, energy-dispersive X-ray diffraction, X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy. The AuNPs were spherically shaped with an average size of 16.1 nm. Further, the subminimum inhibitory concentrations (MICs) of AuNPs (50, 100, and 150 µg/mL) greatly affected the biofilm-forming ability of P. aeruginosa, as observed by crystal violet assay and SEM, which showed a decrease in the number of biofilm-forming cells with increasing AuNP concentration. This was further justified by confocal laser scanning microscopy (CLSM), which showed irregularities in the structure of the biofilm at the sub-MIC of AuNPs. Further, the interaction of AuNPs with PAO1 at the highest sub-MIC (150 µg/mL) showed the internalization of the nanoparticles, probably affecting the tendency of PAO1 to colonize on the surface of the nanoparticles. This study suggests that green-synthesized AuNPs can be used as effective nano-antibiotics against biofilm-related infections caused by P. aeruginosa.

Anticandidal activity of biosynthesized silver nanoparticles: effect on growth, cell morphology, and key virulence attributes of Candida species.

Purpose: The pathogenicity in Candida spp was attributed by several virulence factors such as production of tissue damaging extracellular enzymes, germ tube formation, hyphal morphogenesis and establishment of drug resistant biofilm. The objective of present study was to investigate the effects of silver nanoparticles (AgNPs) on growth, cell morphology and key virulence attributes of Candida species. Methods: AgNPs were synthesized by the using seed extract of Syzygium cumini (Sc), and were characterized by UV-Vis spectrophotometer, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and transmission electron microscopy (TEM). ScAgNPs were used to evaluate their antifungal and antibacterial activity as well as their potent inhibitory effects on germ tube and biofilm formation and extracellular enzymes viz. phospholipases, proteinases, lipases and hemolysin secreted by Candida spp. Results: The MICs values of ScAgNPs were ranged from 0.125-0.250 mg/ml, whereas the MBCs and MFCs were 0.250 and 0.500 mg/ml, respectively. ScAgNPs significantly inhibit the production of phospholipases by 82.2, 75.7, 78.7, 62.5, and 65.8%; proteinases by 82.0, 72.0, 77.5, 67.0, and 83.7%; lipase by 69.4, 58.8, 60.0, 42.9, and 65.0%; and hemolysin by 62.8, 69.7, 67.2, 73.1, and 70.2% in C. albicans, C. tropicalis, C. dubliniensis, C. parapsilosis and C. krusei, respectively, at 500 µg/ml. ScAgNPs inhibit germ tube formation in C. albicans up to 97.1% at 0.25 mg/ml. LIVE/DEAD staining results showed that ScAgNPs almost completely inhibit biofilm formation in C. albicans. TEM analysis shows that ScAgNPs not only anchored onto the cell surface but also penetrated and accumulated in the cytoplasm that causes severe damage to the cell wall and cytoplasmic membrane. Conclusion: To summarize, the biosynthesized ScAgNPs strongly suppressed the multiplication, germ tube and biofilm formation and most importantly secretion of hydrolytic enzymes (viz. phospholipases, proteinases, lipases and hemolysin) by Candia spp. The present research work open several avenues of further study, such as to explore the molecular mechanism of inhibition of germ tubes and biofilm formation and suppression of production of various hydrolytic enzymes by Candida spp.

Forensic analysis of Sync.com and FlipDrive cloud applications on Android platform.

The complex architecture and legal restrictions associated with cloud services make the acquisition of data from servers almost impossible in digital investigations involving cloud services. However, smartphones used to access these cloud services can serve as potential sources. In this paper, we investigate Sync.com and FlipDrive cloud client applications on Android platform for artefacts left behind by user activities. Our experiments demonstrate that rich information arising from user activities is left behind by these applications. This information includes installation details, login credentials, names and timestamps of files uploaded, downloaded, deleted and shared. The study also identifies mechanisms for extracting these artefacts from the devices. These findings assist forensic investigators in performing complete, credible and conclusive digital investigation by allowing them to create complete file management history of these applications. Finally, based on these findings, we make many recommendations relevant to the digital investigation involving these applications.

Antibiotic resistant zoonotic bacteria in Irrawaddy squirrel (Callosciurus pygerythrus).

Irrawaddy squirrel (Callosciurus pygerythrus) may play an important role in the transmission of zoonotic bacteria, but little is known about the carriage of zoonotic bacteria in this common frugivorous rodent in Bangladesh. We aimed to investigate the presence of common zoonotic bacterial pathogens in Irrawaddy squirrel in the southeast part of Bangladesh. A total of 27 rectal and 27 oro-nasal swabs were collected from 27 healthy wild Irrawaddy squirrels. Four common zoonotic bacteria were isolated following routine laboratory procedures, and were identified based on colony morphology, and biochemical and staining properties. The pathogenic potential of the identified bacteria was confirmed by detection of virulence genes by PCR. All isolates were subjected to antimicrobial susceptibility test against seven antibiotics from six generic groups which are commonly used in human and veterinary medicine in Bangladesh. The prevalence of Escherichia coli, Salmonella spp., Yersinia spp. and Staphylococcus spp. was 44.4% (95% CI, 32.0-57.6), 13% (95% CI, 6.1-24.7), 44.4% (95% CI, 32.0-57.6), and 72.2% (95% CI, 59.0-82.5), respectively. We identified potential zoonotic virulence genes in all of these four bacterial species. Antimicrobial susceptibility testing revealed the presence of several multidrug resistant bacterial strains in squirrels. To the best of our knowledge, this is the first report in Bangladesh of the detection of antibiotic resistant zoonotic bacteria in Irrawaddy squirrels. The findings underpin the role of Irrawaddy squirrel as a source of pathogenic antibiotic resistant bacteria, consequently, fruit rejected because of squirrel consumption and squirrel-bites deserve more concern than previously.

Validation of real-time reverse transcription polymerase chain reaction to detect virus titer and thermostability of Newcastle disease live virus vaccine.

BACKGROUND AND AIM: Newcastle disease is one of the most common diseases affecting poultry in Bangladesh. The disease can cause up to 100% mortality but is preventable if birds are timely and properly vaccinated with a vaccine of standard virus titer. Different live vaccines are commercially available in the country - most, if not all, are produced using lentogenic strains of the virus with variable virulence. One of the disadvantages of these vaccines is that they are not stable at high environmental temperature, and therefore, a proper cold chain must be maintained during transportation and storage. Information on how long these vaccine viruses can withstand environmental temperature, which is near the vicinity of 37°C in the summer season in Bangladesh, is scanty. The aim of this research was to measure the effect of temperature on virus titer of live ND virus vaccines and to develop a real-time reverse transcription polymerase chain reaction (rRT-PCR) standard curve to indirectly determine hemagglutination (HA) titer of virus by this highly sensitive method. MATERIALS AND METHODS: In this study, thermostability of five commercial live vaccines containing LaSota, F, Clone 30, and B1 type LaSota strains was observed for up to 35 days keeping them at 37°C. From the most thermostability yielding sample, two rRT-PCR standard curves were developed: (1) By plotting the cycle threshold (CT) values as obtained from 10-fold serial dilutions up to 10-3 against their corresponding log (to the base 10) dilutions and (2) by plotting the CT values obtained from serial HA dilutions up to 2-4 against their corresponding HA titer dilutions. The PCR efficiencies based on which the graphs were fitted were also evaluated. RESULTS: The vaccine from the LaSota strain withstood 37°C for 35 days with a gradual declination of HA titer over time, and this vaccine also had the highest initial HA titer, which was 211. The vaccine made from F strain was inactivated quickly, and it had the lowest HA titer at the beginning of the study. The first standard curve developed can be used to assess the level of virus titer in a diluted sample compared with the titer in the original undiluted vaccine preparation by plotting the CT value obtained from the dilution by rRT-PCR. The second standard curve can be used to calculate the HA titer of a vaccine dilution by plotting the CT value as obtained from the dilution by rRT-PCR. CONCLUSION: The regression equations for the first and second graphs were y=-3.535x+14.365 and y=-1.081x+13.703, respectively, suggesting that, for every 3.53 cycles, the PCR product would have increased 10 times and 2 times for every 1.08 cycles, respectively, indicating nearly (but not exactly) 100% PCR efficiency.

Biosynthesis of Silver Nanoparticles from Oropharyngeal Candida glabrata Isolates and Their Antimicrobial Activity against Clinical Strains of Bacteria and Fungi.

The objective of the present study was one step extracellular biosynthesis of silver nanoparticles (AgNPs) using supernatant of Candida glabrata isolated from oropharyngeal mucosa of human immunodeficiency virus (HIV) patients and evaluation of their antibacterial and antifungal potential against human pathogenic bacteria and fungi. The mycosynthesized AgNPs were characterized by color visualization, ultraviolet-visible (UV) spectroscopy, fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The FTIR spectra revealed the binding and stabilization of nanoparticles with protein. The TEM analysis showed that nanoparticles were well dispersed and predominantly spherical in shape within the size range of 2⁻15 nm. The antibacterial and antifungal potential of AgNPs were characterized by determining minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC)/ minimum fungicidal concentration (MFC), and well diffusion methods. The MBC and MFC were found in the range of 62.5⁻250 µg/mL and 125⁻500 µg/mL, which revealed that bacterial strains were more susceptible to AgNPs than fungal strains. These differences in bactericidal and fungicidal concentrations of the AgNPs were due to the differences in the cell structure and organization of bacteria and yeast cells. The interaction of AgNPs with C. albicans analyzed by TEM showed the penetration of nanoparticles inside the Candida cells, which led the formation of "pits" and "pores" that result from the rupturing of the cell wall and membrane. Further, TEM analysis showed that Candida cells treated with AgNPs were highly deformed and the cells had shrunken to a greater extent because of their interaction with the fungal cell wall and membrane, which disrupted the structure of the cell membrane and inhibited the normal budding process due to the destruction and loss of membrane integrity and formation of pores that may led to the cell death.

Anticandidal activity of bioinspired ZnO NPs: effect on growth, cell morphology and key virulence attributes of Candida species.

The pathogenicity of Candida species in human is dependent on a variety of virulence factor such as adhesion factors, germ tube and hyphal formation, secretion of hydrolytic phospholipases and proteinases and drug resistance biofilm. ZnO NPs have been synthesized by using leaf extract of Crinum latifolium and were characterized by UV-Vis spectrophotometer, FTIR, SEM, EDX and TEM. In this study for the first time, potent inhibitory effects of ZnO NPs on principal virulence factors of Candida albicans and non-albicans such as germ tube formation, secretion of hydrolytic phospholipases and proteinases and biofilm formation has been investigated. ZnO NPs remarkably reduced the germ tube formation of C. albicans at 1 (86.4%), 0.5 (75.0%), 0.25 (61.4%), 0.125 (34.1%) and 0.062 mg/ml (11.4%). ZnO NPs significantly lowered the phospholipase and proteinase secretion by 58.8 and 95.2% at 0.25 mg/ml, respectively. CSLM results showed that ZnO NPs suppressed biofilm formation up to 85% at 0.25 mg/ml. SEM and TEM micrograph showed that ZnO NPs penetrated inside the cell and causes extensive damaged in cell wall and cell membrane. Inhibition of Candida growth and various virulent factors by ZnO NPs provides an insight towards their therapeutic application for the treatment of Candida-associated infections.

Antiquorum sensing activity of silver nanoparticles in P. aeruginosa: an in silico study.

Pseudomonas aeruginosa an opportunistic pathogen regulates its virulence through Quorum sensing (QS) mechanism comprising of Las and Rhl system. Targeting of QS mechanism could be an ideal strategy to combat infection caused by P. aeruginosa. Silver nanoparticles (AgNPs) have been broadly applied as antimicrobial agents against a number of pathogenic bacterial and fungal strains, but have not been reported as an anti-QS agent. Therefore, the aim of present work was to show the computational analysis for the interaction of AgNPs with the QS system using an In silico approach. In silico studies showed that AgNPs got 'locked' deeply into the active site of respective proteins with their surrounding residues. The molecular docking analysis clearly demonstrated that AgNPs got bound to the catalytic cleft of LasI synthase (Asp73-Ag = 3.1 Å), RhlI synthase (His52-Ag = 2.8 Å), transcriptional receptor protein LasR (Leu159-Ag = 2.3 Å) and RhlR (Trp10-Ag = 3.1 Å and Glu34-Ag = 3.2 Å). The inhibition of LasI/RhlI synthase by AgNPs blocked the biosynthesis of AHLs, thus no AHL produced, no QS occurred. Further, interference with transcriptional regulatory proteins led to the inactivation of LasR/RhlR system that finally blocked the expression of QS-controlled virulence genes. Our findings clearly demonstrate the anti-QS property of AgNPs in P. aeruginosa which could be an alternative approach to the use of traditional antibiotics for the treatment of P. aeruginosa infection.

A Highly Structured 1,10-Phenanthroline Arrayed Hydrophobic Sulfone Membrane Platform for the Rapid Determination and Speciation of Fe2+/Fe3+ Ions in Water.

An optical assay for the rapid determination and chemical speciation of Fe2+/Fe3+ species has been proposed for the first time on a polyether sulfone (PES) membrane platform. The small pore size and low wettability (θ ∼82°) of the membrane disallowed the dissipation of analyte droplets on the surface, thus localizing it onto nanoliter arrayed 1,10-phenanthroline spots. Under optimized conditions and within ∼5 min, an acceptable limit of detection (0.1 µg mL-1) and linear dynamic range (1 - 100 µg mL-1) were achieved. The proposed method was also successfully applied for indirect determination of Fe3+ ions in synthetic samples after reduction to Fe2+ using SO2. The performance of the proposed sensor was validated for its robustness and stability. Due to high selectivity and accuracy, the method was satisfactorily applied for the analysis of Fe2+/Fe3+ species in marine water samples. The proposed method is an easy and low-cost system coupled with good reproducibility and ruggedness, applicable for point-of-use testing.

Biodegradation of low and high molecular weight hydrocarbons in petroleum refinery wastewater by a thermophilic bacterial consortium.

Clean-up of contaminated wastewater remains to be a major challenge in petroleum refinery. Here, we describe the capacity of a bacterial consortium enriched from crude oil drilling site in Al-Khobar, Saudi Arabia, to utilize polycyclic aromatic hydrocarbons (PAHs) as sole carbon source at 60°C. The consortium reduced low molecular weight (LMW; naphthalene, phenanthrene, fluorene and anthracene) and high molecular weight (HMW; pyrene, benzo(e)pyrene and benzo(k)fluoranthene) PAH loads of up to 1.5 g/L with removal efficiencies of 90% and 80% within 10 days. PAH biodegradation was verified by the presence of PAH metabolites and evolution of carbon dioxide (90 ± 3%). Biodegradation led to a reduction of the surface tension to 34 ± 1 mN/m thus suggesting biosurfactant production by the consortium. Phylogenetic analysis of the consortium revealed the presence of the thermophilic PAH degrader Pseudomonas aeruginosa strain CEES1 (KU664514) and Bacillus thermosaudia (KU664515) strain CEES2. The consortium was further found to treat petroleum wastewater in continuous stirred tank reactor with 96 ± 2% chemical oxygen demand removal and complete PAH degradation in 24 days.

Crataeva nurvala nanoparticles inhibit virulence factors and biofilm formation in clinical isolates of Pseudomonas aeruginosa.

Green synthesized nanoparticles have gained great attention due to their non-toxic and non-hazardous nature. In the present study, bark extract of the medicinal plant in Ayurveda Crataeva nurvala (Buch-Ham) (CN) was chosen for the biosynthesis of silver nanoparticles (AgNPs). These NPs were characterized by Ultra violet visible spectroscopy, Fourier Transform Infra Red, Atomic Force Microscopy, and Transmission Electron Microscopy (TEM). The average particle size of green synthesized CN-AgNPs was 15.2 ± 1.01 nm. Gas chromatography- mass spectrometry analysis of methanolic bark extract involved in the formation of CN-AgNPs revealed lupeol as a major active component. In this study, CN-AgNPs (15 µg ml-1 ) efficiently suppressed the production of quorum sensing mediated virulence factors viz. pyocyanin, protease, hemolysin, and biofilm formation in Pseudomonas aeruginosa. The pyocyanin production was strongly inhibited (74.64%) followed by proteolysis (47.3%) and hemolysin production (47.7%). However, the biofilm forming ability was maximally reduced up to 79.70%. Moreover, the Confocal Laser Scanning Microscopic Analysis showed that CN-AgNPs inhibit colonization of P. aeruginosa on to the surface. Furthermore, TEM analysis revealed internalization of CN-AgNPs inside the bacterial cell. It is concluded that green synthesized AgNPs have great potential to inhibit virulence factors and biofilm forming ability of drug-resistant clinical isolates of P. aeruginosa.

Green synthesis of Al2O3 nanoparticles and their bactericidal potential against clinical isolates of multi-drug resistant Pseudomonas aeruginosa.

The high prevalence of extended-spectrum ß-lactamases (76.3 %) and metallo-ß-lactamases (7.3 %) amongst the bacteria Pseudomonas aeruginosa is a critical problem that has set forth an enormous therapeutic challenge. The suggested role of nanoparticles as next generation antibiotics, and inadequate information on antibacterial activity of aluminium oxide nanoparticles has led us to investigate the green synthesis of aluminium oxide nanoparticles (Al2O3 NPs) using leaf extracts of lemongrass and its antibacterial activity against extended-spectrum ß-lactamases and metallo-ß-lactamases clinical isolates of P. aeruginosa. The synthesized Al2O3-NPs were characterized by scanning electron microcopy, high resolution-transmission electron microscopy, atomic force microscopy, X-ray diffraction, Zeta potential, and differential light scattering techniques. The X-ray diffraction data revealed the average size of the spherical Al2O3-NPs as 34.5 nm. The hydrodynamic size in Milli Q water and Zeta potential were determined to be 254 nm and +52.2 mV, respectively. The minimal inhibitory concentration of Al2O3-NPs was found to be in the range of 1,600-3,200 µg/ml. Treatment at concentrations >2,000 µg/ml, resulted in complete growth inhibition of extended-spectrum ß-lactamases and metallo-ß-lactamases isolates. Scanning electron microcopy analysis revealed the clusters of nanoparticles attached to the bacterial cell surface, causing structural deformities in treated cells. High resolution-transmission electron microscopy analysis confirmed that nanoparticles crossed the cell membrane to become intracellular. The interaction of nanoparticles with the cell membrane eventually triggered the loss of membrane integrity, most likely due to intracellular oxidative stress. The data explicitly suggested that the synthesized Al2O3-NPs can be exploited as an effective bactericidal agent against extended-spectrum ß-lactamases, non-extended-spectrum ß-lactamases and metallo-ß-lactamases strains of P. aeruginosa, regardless of their drug resistance patterns and mechanisms. The results elucidated the clinical significance of Al2O3-NPs in developing an effective antibacterial therapeutic regimen against the multi-drug resistant bacterial infections. The use of leaf extract of lemongrass for the synthesis of Al2O3-NPs appears to be cost effective, nontoxic, eco-friendly and its strong antibacterial activity against multi-drug resistant strains of P. aeruginosa offers compatibility for pharmaceutical and other biomedical applications.