Effects of Nano-Scale Zero Valent Iron Fresh and Aged Particles on Environmental Microbes

Currently, nano-scale zero valent iron particles (nZVI) are being increasingly used in many types of environmental remediation. Due to their usage, nZVI can be left in the environment and may cause toxic effects to living beings, especially surrounding microorganisms. Environmental bacteria in soil and water are some of the main factors affecting plant productivity and other microorganisms in ecosystems. This study evaluated the toxicological effects of nZVI and aged nZVI on bacteria commonly found in the environment. Bacterial, namely E. coli, P. aeruginosa, S. aureus, B. subtilis, and Rhodococcus sp., were treated with different concentrations of nZVI at different times of exposure in in vitro conditions, and bacterial cell viability was determined in order to analyze the toxic effects of nZVI over the course of treatments. The data revealed that at the highest nZVI concentration (1,000 mg/L), B. subtilis and Rhodococcus sp. had the highest resistance to nZVI (49.35% and 48.31% viability) and less resistance in P. aeruginosa (2.26%) and E. coli (0.50%) was observed. The growth of microorganisms significantly increased after exposure with seven and 14-day aged nZVI particles. Therefore, the toxicity of aged nZVI to microbial organisms was reduced. Hence, this study demonstrated the toxic effects of nZVI and aged nZVI particles on several species of bacteria in vitro. Less toxicity to bacteria was observed in aged nZVI. These findings provide more understanding in the toxic effect of nZVI to microorganisms.

Detecting Bacterial Cell Viability in Few µL Solutions from Impedance Measurements on Silicon-Based Biochips

Using two different types of impedance biochips (PS5 and BS5) with ring top electrodes, a distinct change of measured impedance has been detected after adding 1–5 µL (with dead or live Gram-positive Lysinibacillus sphaericus JG-A12 cells to 20 µL DI water inside the ring top electrode. We relate observed change of measured impedance to change of membrane potential of L. sphaericus JG-A12 cells. In contrast to impedance measurements, optical density (OD) measurements cannot be used to distinguish between dead and live cells. Dead L. sphaericus JG-A12 cells have been obtained by adding 0.02 mg/mL of the antibiotics tetracycline and 0.1 mg/mL chloramphenicol to a batch with OD0.5 and by incubation for 24 h, 30 °C, 120 rpm in the dark. For impedance measurements, we have used batches with a cell density of 25.5 × 108 cells/mL (OD8.5) and 270.0 × 108 cells/mL (OD90.0). The impedance biochip PS5 can be used to detect the more resistive and less capacitive live L. sphaericus JG-A12 cells. Also, the impedance biochip BS5 can be used to detect the less resistive and more capacitive dead L. sphaericus JG-A12 cells. An outlook on the application of the impedance biochips for high-throughput drug screening, e.g., against multi-drug-resistant Gram-positive bacteria, is given.

Removal of aflatoxin b1 and t-2 toxin by bacteria isolated from commercially available probiotic dairy foods

This study isolated lactic acid bacteria from commercially available probiotic foods to determine their capacity to remove aflatoxin B1 (AFB1) and trichothecene-2 (T-2). The removal rates by original live and heat-treated cells of lactic acid bacteria (LAB) were compared to test the effect of heat treatment on efficacy. LAB is capable to remove up to 46% of AFB1 and up to 45% of T-2 toixn. The toxin removal capability increased as toxin concentration increased despite bacterial cell viability declining. Surprisingly, the denatured LAB removed greater percentages of AFB1 (up to 62%) and T-2 (up to 52%) than live bacterial cells ( P < 0.05), lending support to the hypothesis that there is higher binding of toxins to the cell membrane of nonviable cells. The research provided practical evidences, which suggest that when ingested into the gut biota, LAB could likely reduce absorption of AFB1 and T-2 from contaminated foods.

Fabrication of silver doped nano hydroxyapatite-carrageenan hydrogels for articular cartilage applications

It can be found from the results that nano hydroxyapatite- silver -3.0 wt% carageenan (nHA-Ag-CG3.0) improved the mechanical properties of the as-formed hydrogel scaffold after incorporation of higher CG concentration. The Young’s modulus of hydroxyapatite- silver - 1.5wt% carageenan (nHA-Ag-CG1.5) was found to be 0.36 ± 0.07 MPa that increased in case of nHA-Ag-CG3.0 demonstrating better interfacial compatibility of their matrix with respect to the reinforcement. This increase in reinforcement concentration resulted in higher stiffness that dissipated energy. The higher swelling ratio is envisaged to induce better cell adhesion and proliferation. The biodegradability test was performed in phosphate buffered saline at body temperature for 3 weeks. The biodegradability rate of nHA-Ag-CG1.5 was found to be equivalent to nHA-Ag-CG3.0 hydrogels at day 7 while it increased faster in nHA-Ag-CG3.0 on days 14 and 21 that may be ascribed to the possible interaction of nHA and Ag with their CG matrix. The bacterial cell viability of Staphylococcus aureus (S. aureus) was performed after 10 h, 20 h and 30 h of culture. The nHA-Ag-CG1.5 exhibited restrained growth of S. aureus as compared to nHA-Ag-CG3.0 and these results were validated by CLSM analysis. Hence, nHA-Ag-CG3.0 may be considered to have more cytocompatibility than nHA-Ag-CG 1.5.

Unexpected Cell Wall Alteration-Mediated Bactericidal Activity of the Antifungal Caspofungin against Vancomycin-Resistant Enterococcus faecium

ABSTRACT Enterococcus faecium has become a major opportunistic pathogen with the emergence of vancomycin-resistant enterococci (VRE). As part of the gut microbiota, they have to cope with numerous stresses, including effects of antibiotics and other xenobiotics, especially in patients hospitalized in intensive care units (ICUs) who receive many medications. The aim of this study was to investigate the impact of the most frequently prescribed xenobiotics for ICU patients on fitness, pathogenicity, and antimicrobial resistance of the vanB-positive E. faecium Aus0004 reference strain. Several phenotypic analyses were carried out, and we observed that caspofungin, an antifungal agent belonging to the family of echinocandins, had an important effect on E. faecium growth in vitro. We confirmed this effect by electron microscopy and peptidoglycan analysis and showed that, even at a subinhibitory concentration (1/4× MIC, 8 mg/liter), caspofungin had an impact on cell wall organization, especially with respect to the abundance of some muropeptide precursors. By transcriptome sequencing (RNA-seq), it was also shown that around 20% of the transcriptome was altered in the presence of caspofungin, with 321 and 259 significantly upregulated and downregulated genes, respectively. Since the fungal target of caspofungin (i.e., β-1,3-glucan synthase) was absent in bacteria, the mechanistic pathway of caspofungin activity was investigated. The repression of genes involved in the metabolism of pyruvate seemed to have a drastic impact on bacterial cell viability, while a decrease of glycerol metabolism could explain the conformational modifications of peptidoglycan. This is the first report of caspofungin antibacterial activity against E. faecium, highlighting the potential impact of nonantibiotic xenobiotics against bacterial pathogens.

Electrochemical Evaluation of Bacterial Activity

For the efficient utilization of bacterial bioresources, the quantitative evaluation of metabolic activity in live bacterial cells is required. Using potentiometric measurements, we quantitatively evaluated the electron generation rate of Shewanella oneidensis MR-1 based on individual enzymatic reactions. We evaluated intracellular electron generation in bacterial suspensions supplemented with different carbon sources utilized in the tricarboxylic acid cycle. In bacterial suspensions, ferricyanide was almost completely reduced to ferrocyanide by cell-generated electrons, without an effect on bacterial cell viability. Focusing on this reduction reaction, quantitative evaluations were possible by potentiometry based on the Nernst equation.

The effect of the surgical hemostatic product «Hemoblock»TM on in vitro bacterial colonization

Objective. To evaluate effect of «Haemoblock»TM preparation on in vitro bacterial colonization. Materials and Methods. Activity of «Haemoblock»ТМ product on the growth and colonization of S. aureus АТСС 25923, S. epidermidis ATCC 28922, E. coli АТСС 25922, P. aeruginosa АТСС 27853 cells in the suspension and on the surface of monofilament macroporous polyester mesh was evaluated. Results. This product at concentration of 0.062% and above inhibited bacterial growth and reduced biofilm mass and bacterial cell viability. In addition, the short-term exposure of the mesh implant to the tested product resulted in inhibition of the abiotic surface contamination. Conclusions. «Haemoblock»TM product allows not only to ensure hemostasis in open and laparoscopic surgery, but also to reduce the bacterial cell count in the surrounding tissues in the intra- and post-operative periods.

DEVELOPMENT OF AZITHROMYCIN LOADED LEMONGRASS OIL BASED MICROEMULSION AND DETERMINATION OF ANTIBACTERIAL POTENTIAL

Objective: Azithromycin (AZM), an azalide drug is used to treat bacterial infections. It is poorly water-soluble, with low human bioavailability due to partial absorption. This can be improved using a microemulsion drug delivery system using essential oil.Methods: Microemulsion system was prepared with AZM solubilized lemongrass oil (Cymbopogon citratus), Tween 20 and water containing 1% (v/v) 10 mmol sodium hydroxide. In vitro drug release was determined using a 14KDa semipermeable dialysis membrane. The kinetics of bacterial killing was done at MIC concentrations, and viable counts were determined hourly for 24 h. Bacterial cell viability was determined by differential staining with acridine orange and ethidium bromide. In vitro toxicity was determined by the MTT assay, while in vivo toxicity was determined in male Wistar rats.Results: The optimized formulation (5:20:75 %) was thermodynamically stable with drug solubility of 366.90 mg/ml and a droplet diameter of 12.4±3.9 nm, which do not show in vivo or in vitro toxicity. In vitro drug release study in simulated body fluids revealed a controlled drug release from microemulsion-based formulation. The MIC was 1μg/ml and 2μg/ml against Staphylococcus aureus and Escherichia coli respectively. In vitro kill kinetics showed>2 log10 killing by 8 h. Bacterial cell viability assay and scanning electron microscopy analysis further confirmed substantial morphological changes due to alteration in the cell membrane.Conclusion: The reduced droplet size and the inherent antibacterial property of lemongrass oil enhanced the efficacy of the AZM loaded ME system in comparison with the bulk drug, against the bacterial pathogens.