Electrochemical biotesting technique as applied to comparative assessment of antimicrobial properties of essential oils

A biotesting technique is described that provides for periodic (every 2 hours) recording of changes in pH, redox potential, and electrical conductivity of a liquid culture medium incubated in the presence and in the absence of viable test microorganisms (TM) and test samples (TS). The results of a comparative analysis using this technique of antibiotic activity against Staphylococcus aureus of different concentrations of «essential oils» obtained from 10 types of plant raw materials are presented. Based on this, we can conclude the following. Using the presented methodology, it is possible to assess the effect on the dynamics of the vital activity of TM of samples of various pharmaceutical, cosmetic, food, feed and other products, much more quickly, objectively and informatively than using standard visual methods of microbiological testing. The initial antibiotic activity of TS in most cases was greater than their prolonged antibiotic activity. At the same time, the mid-term (in terms of the time of interaction of TS with TM) antibiotic activity of TS was usually intermediate in value between their initial and prolonged biological activity.

CLAY AS A SUBSTRATUM MATERIAL FOR MICROALGAE BIOFILM CULTIVATION

The production of microalgae faces several obstacles. The bioreactors and processes used today in microalgae cultivation are expensive or lack optimization to scale up. Furthermore, harvesting, concentrating and dewatering, while using a cheap and suitable photobioreactor are the main problems that we need to be overcome to achieve viability in the process. The Clay Ceramic Bioreactor (CCBR) was built using only clay and wood sawdust and was designed to grow an immobilized microalgal biofilm while having almost complete separation from the liquid culture medium, reducing the consumption of water and energy. Results showed that the wood sawdust particle size should be sifted in a mesh size 10 and mixed in a proportion of 33% of sawdust and 67% of red clay and a maximum firing temperature of 900oC. Maximum dry biomass production of 3.71 g.m-2.d-1 was achieved within 7 days of cultivation, with no CO2 addition and a low light intensity of 45 µmol.m?2.s?1. The biomass was harvested through simple scraping. Initial results indicate a great potential for the use of clay as substratum and further tests should be carried out to scale up and optimize microalgae production,

CLAY AS A SUBSTRATUM MATERIAL FOR MICROALGAE BIOFILM CULTIVATION

The production of microalgae faces several obstacles. The bioreactors and processes used today in microalgae cultivation are expensive or lack optimization to scale up. Furthermore, harvesting, concentrating and dewatering, while using a cheap and suitable photobioreactor are the main problems that we need to be overcome to achieve viability in the process. The Clay Ceramic Bioreactor (CCBR) was built using only clay and wood sawdust and was designed to grow an immobilized microalgal biofilm while having almost complete separation from the liquid culture medium, reducing the consumption of water and energy. Results showed that the wood sawdust particle size should be sifted in a mesh size 10 and mixed in a proportion of 33% of sawdust and 67% of red clay and a maximum firing temperature of 900oC. Maximum dry biomass production of 3.71 g.m-2.d-1 was achieved within 7 days of cultivation, with no CO2 addition and a low light intensity of 45 µmol.m?2.s?1. The biomass was harvested through simple scraping. Initial results indicate a great potential for the use of clay as substratum and further tests should be carried out to scale up and optimize microalgae production,

Bacteriophages with Potential to Inactivate Aeromonas hydrophila in Cockles: In Vitro and In Vivo Preliminary Studies

The recurrent emergence of infection outbreaks associated with shellfish consumption is of extreme importance for public health. The present study investigated the potential application of phages AH-1, AH-4, and AH-5 to inactivate Aeromonas hydrophila, a causative agent of infections in humans associated with bivalve shellfish consumption. The inactivation of A. hydrophila was assessed in vitro, using a liquid culture medium, and in vivo, using artificially contaminated cockles with A. hydrophila ATCC 7966. In the in vitro experiments, all phages were effective against A. hydrophila, but phage AH-1 (with a maximum reduction of 7.7 log colonies forming units CFU/mL) was more effective than phages AH-4 and AH-5 (with reductions of 4.9 and 4.5 log CFU/mL, respectively). The cocktails AH-1/AH-4, AH-1/AH-5, AH-4/AH-5, and AH-1/AH-4/AH-5 were slightly more effective than the single phage suspensions. The phages presented a low emergence rate of phage-resistant mutants. When artificially contaminated cockles were treated in static seawater with phage AH-1, around 44% of the added A. hydrophila (1.0 log CFU/g) was inactivated. The results of this study suggest that phage therapy can be an effective alternative to control human pathogenic bacteria during depuration.

Lipid Secretion by Parasitic Cells of Coccidioides Contributes to Disseminated Disease

Coccidioides is a soil-borne fungal pathogen and causative agent of a human respiratory disease (coccidioidomycosis) endemic to semi-desert regions of southwestern United States, Mexico, Central and South America. Aerosolized arthroconidia inhaled by the mammalian host first undergo conversion to large parasitic cells (spherules, 80–100 μm diameter) followed by endosporulation, a process by which the contents of spherules give rise to multiple endospores. The latter are released upon rupture of the maternal spherules and establish new foci of lung infection. A novel feature of spherule maturation prior to endosporulation is the secretion of a lipid-rich, membranous cell surface layer shed in vivo during growth of the parasitic cells and secretion into liquid culture medium during in vitro growth. Chemical analysis of the culture derived spherule outer wall (SOW) fraction showed that it is composed largely of phospholipids and is enriched with saturated fatty acids, including myristic, palmitic, elaidic, oleic, and stearic acid. NMR revealed the presence of monosaccharide- and disaccharide-linked acylglycerols and sphingolipids. The major sphingolipid components are sphingosine and ceramide. Primary neutrophils derived from healthy C57BL/6 and DBA/2 mice incubated with SOW lipids revealed a significant reduction in fungicidal activity against viable Coccidioides arthroconidia compared to incubation of neutrophils with arthroconidia alone. Host cell exposure to SOW lipids had no effect on neutrophil viability. Furthermore, C57BL/6 mice that were challenged subcutaneously with Coccidioides arthroconidia in the presence of the isolated SOW fraction developed disseminated disease, while control mice challenged with arthroconidia alone by the same route showed no dissemination of infection. We hypothesize that SOW lipids contribute to suppression of inflammatory response to Coccidioides infection. Studies are underway to characterize the immunosuppressive mechanism(s) of SOW lipids.

Drug sensitivity of low growing non-­­tuberculous mycobactria

Objective — analysis of drug resistance (DR) of some types of low growing non-­tuberculous mycobactria (NTMB) by the method of double serial microdilutions of drugs of different groups to determine the minimum inhibitory concentra­tions (MIC) in a liquid culture medium using the TREK Diagnostic Systems test system, Thermo Scientific SLOWMYCO for low growing mycobacteria. Materials and methods. Investigated 122 strains of low growing NTMB (M. avium, M. intracellulare, M. gordonae, M. kansasii, M. xenopi, M. malmoense and M. simiae), which were isolated in a liquid nutrient medium during sputum inoculation. DR was determined by the culture method using the TREK Diagnos­tic Systems kits (panel for low growing NTMB, which allows to determine the MIC of 13 drugs). The results were interpreted using an automatic bacteriological analyzer Sensititre Vizion System TREK Diagnostic Systems (USA). Results and discussion. Was found that for most M. avium strains the MIC of amikacin was 16.0—32.0 µg/ml, for ciprofloxacin — 16.0 µg/ml and higher, clarithromycin — 2.0—4.0 µg/ml, doxycycline — 16.0 µg/ml and above, ethambutol — 8.0—16.0 µg/ml. The MIC spectrum of ethionamide was distributed in the range from 1.2 to more than 20.0 µg/ml. MIC of isoniazid for most strains of M. avium was more than 8.0 µg/ml, linezolid — 16.0—32.0 µg/ml, moxifloxacin — 2.0—4.0 µg/ml, rifabutin — 0.25 µg/ml, rifampicin 4.0 µg/ml and above, streptomycin 64 µg/ml and above, and trimethoprim/sulfamethoxazole — more than 8.0/152 µg/ml. For M. intracellulare strains, in general, a similar situation with the M. avium strains with the MIC spectrum was observed. The work also provides MICs for the strains M. gordonae, M. kansasii, M. xenopi, M. simiae and M. malmoense. Based on the determination of the DR, the MIC50 and MIC90 values of each preparation of the SLOWMYCO panel were calculated for the studied species of low growing NTMB. Comparison of the MIC50 and MIC90 values with the limiting drug concentrations made it possible to determine the drugs effective against the studied types of NTMs. Conclusions. Determination of DR by the micromethod of serial dilutions in a liquid nutrient medium showed that most of the studied strains of low growing NTMPs are sensitive to clarithromycin and rifabutin. Amikacin, linezolid, and moxifloxacin were also quite effective. At the same time, drugs such as ethambutol, isoniazid, streptomycin, trimethoprim/sulfamethoxazole, suppressed the growth of the studied strains mainly in high concentrations, significantly exceeding the critical one.Until now, there is no single criterion for determining the DR NTM, and for the method used in this work, recommended by the Institute for Clinical and Laboratory Standards (USA), there are limitations in the interpretation of the results due to the untreated limit concentrations of drugs for various types of NTM. This is especially true for MAC, which play a major role in the development of mycobacteriosis. It was shown that the resistance profile of M. avium strains included the largest number of SLOWMYCO panel preparations compared to other types of NTMB, which dictates the need for studies aimed at comparing the results of in vitro DST with the effectiveness of therapy.

Sorption of Zinc by exopolysaccharides produced by liquid media of phytopatogenic fungi

Phytopathogenic fungi such as: Colletotrichum gloeosporioides and Rhizopus stolonifer were cultivated in three different liquid culture media: LCC (glucose 40 g L-1 , yeast extract 3 g L-1 ), LC2 (glucose 40 g L-1 , yeast extract 3 g L-1 and tryptone peptone 2 g L-1 ) and LC3 (glucose 40 g L-1 , yeast extract 3 g L-1 and tryptone peptone 10 g L-1 ) under pH of 5.5 for the production of mycelial biomass and exopolysaccharides (EPS). The liquid culture medium (LC3) used in cultivation of Colletotrichum gloeosporioides showed the highest production of biomass (15.40 g L-1 ) and exopolysaccharides (3.40 g L-1 ). Exopolysaccharides (EPS) obtained from the liquid culture medium (LC3) of Colletotrichum gloeosporioides presented the highest absorption content of Zinc (56 mg g-1 ). The results presented that the exopolysaccharides (EPS) produced by Colletotrichum gloeosporioides showed the greatest biosorbent capacity of Zinc (Zn) using the culture medium with the highest amount of tryptone peptone.

Исследование электрофизических свойств композиционных волокон на основе хитозана и полипиррола для тканевой инженерии

Composite fibers based on chitosan, coated with a conducting polymer, polypyrrole (PPyr), have been obtained. Their morphology was studied by scanning electron microscopy. The electrical conductivity of the fibers in a dry state and in a liquid culture medium simulating tissue fluid has been estimated. The values of resistivity, ro, and conductivity, sigma , of the investigated fibers are determined depending on the number of PPyr layers, the degree of drawing (orientation) of the fibers in dry and in liquid media. It was found that with an increase in the amount of drawing from 0 to 100%, ro of fibers decreases both in a dry state and in a liquid culture medium. In this case, the maximum drop ro of fibers upon immersion in a liquid culture medium was observed for undrawn fibers with two layers of PPyr. It was shown that after an initial drop in ro of oriented chitosan fibers with 1 and 2 layers of PPyr ro changes weakly in a liquid culture medium for 2 hours. The investigated oriented polymer fibers of chitosan coated with 1 and 2 layers of PPyr are promising for use in the field of tissue engineering and regenerative medicine.