Isolation and characterization of nitrogen-fixing bacteria from soil sample in Dhaka, Bangladesh

Biological nitrogen (N2) fixation is very essential for limiting the growth of plants and agricultural crops. The present study was conducted to potentially isolate N2-fixing bacteria from garden soil sample at Stamford University Bangladesh, Siddeswari, Dhaka. Here, we used culture-dependent method to perform this experiment. Firstly, we collected garden soil sample, diluted and inoculated in N2-free Jensen’s media by maintaining the aseptic procedure. We obtained 5 different colonies from soil samples. We cultured the isolates in N2-free Jensen’s media containing bromothymol blue (BMB) and also, in Yeast Extract Mannitol Agar (YEMA) media containing congo red to confirm nitrogen fixation capacity. We collected the colony characteristics of all the isolates. Only 1A isolate showed good growth after 24 h of incubation among all the isolates. We performed ammonification test with Nessler reagent to confirm N2-fixing ability for our selected isolates. The 1A isolate was positive in ammonification test. Culture, microscopy and biochemical tests were performed to identify isolate 1A. This isolate was presumptively identified as Azotobacter sp. In the present study, Azotobacter sp. that was isolated from the soil sample was found to be a potential N2-fixing bacterium. Isolate 1A can be used for N2-fixation to boost production of crops. Stamford Journal of Microbiology, Vol.11 (1) 2021: 11-13

Effect of shell disinfection with AQUALYTE (NEUTRAL ANOLYTE) on inactivation of Salmonella enteritidis and quality of edible eggs

The results of studies, conducted by a number of scientists, prove that chicken eggs can cause food poisoning, as well as poultry. To prevent foreign microfloraingress into egg products, scientists have developed a number of methods aimed at the pathogenic microflora inactivation on the surface of the table eggs shells; nevertheless, the search for new methods is an urgent task. The article describes the results of the studies on the effect of disinfecting the shells of table eggs using AQUALYTE NEUTRAL ANOLYTE (NA) on the eggs quality. NA disinfecting activity was studied using cambric test objects. For the purposes of studying NA disinfecting efficiency, an experimental contamination of the surface of the table eggs shells with a test culture of Salmonella enteritidis was made. It was established that disinfection of the table eggs shells with 100% (2 min exposure) and 50% (5 min exposure) NA solutions provides Salmonella inactivation on the shell, and it does not affect the veterinary and sanitary parameters of eggs.

Incidental Laboratory Identification of Brucella melitensis in a case with Pancytopenia

Brucellosis is a bacterial zoonosis usually associated with exposure to infected animals or their products. Although a significant public health problem in India, exact prevalence and distribution are unknown owing to the imprecision of diagnosis and inadequacy of reporting and surveillance. Although the febrile illness is common, its manifestations are highly variable. Bone marrow suppression and consequent pancytopenia have been rarely reported. We present a case of 50 years old female diagnosed with human brucellosis associated with pancytopenia and non-specific clinical presentation, that was diagnosed incidentally on blood and bone-marrow culture. This was confirmed by serological tests like the standard agglutination test. Culture isolation using automated blood culture (e.g. BacT/ALERT), followed by identification using automated identification systems (e.g. MALDI-TOF and VITEK-2) help to reach accurate and timely diagnosis aiding in the management of the patient.

Isolation of Thermostable Protease Producing Bacteria from the Microbial Mats

As thermostable protease has more commercial value in different industries, the aim of this study was to search for such an enzyme producing bacteria from the microbial mats. Investigation was continued on the isolate for its ability to produce mass amount of enzyme and its activity under suitable optimized conditions. Different parameters including cheap carbon and nitrogen substrates, inoculum size and temperature was selected to optimize the enzyme production conditions. Initially five different isolates from two microbial mats collected from different sources were analyzed for its ability to produce thermostable protease after exposing to higher temperature incubation conditions. Test culture tentatively named as 1F from microbial mat-1 was selected as more enzyme producer among the ten isolates. The organism was selected based on the zone of clearance on skim milk agar by the isolate, that indicating more protease production. Under each optimization parameter, each type of carbon (Lactose), and nitrogen (yeast extract) source showed more enzyme production and activity respectively. About 1% inoculum size and a thermostable temperature of 45°C produced significant amount of enzyme and its activity. The obtained results emphasized the need for thermostable protease for different commercial industries in the existing and near future.

Features of antifungal therapy during long-lasting infectious process: a clinical case of fungal keratitis and profile of antifungal sensitivity based on assessing biofilm formation

Among infectious diseases, opportunistic mycoses hold a special place. There has been accumulating a lot of evidence regarding the clinical and epidemiological aspects of infection caused by Fusarium spp., which global incidence rate among microbial keratitis ranges from 2 to 40% depending on the geographical location of the country. Colonizing mucous membranes, fungi can exist not only in the form of plankton, but form biofilms after surface attachment, which leads to elevated resistance to multiple antifungal agents. Here we describe a clinical case of fungal keratitis due to Fusarium solani by determining profile of the antifungal sensitivity for isolated fungal strains, by taking into account their potential for biofilm formation. We used an F. solani culture isolated from the patient as well as F. solani test culture obtained from the Russian National Collection of Microorganisms. While determining the sensitivity of fungal planktonic cultures to antifungal agents from the azole group (fluconazole, voriconazole), amphotericin B and terbinafine, it was revealed that antimycotics amphotericin B and voriconazole exerted a marked antifungal activity against clinical isolate, whereas the plankton F. solani test culture was more sensitive to all groups of antifungal agents. Due to a long-lasting progressive course of the infectious process and the high biofilm-forming ability of the clinical strain F. solani, the activity of antifungal agents on biofilm cells was modeled and examined in vitro. It was shown that regarding to the fungal biofilms, value of the minimally inhibitory concentration exceeded those for planktonic cultures by 100-fold. The mechanisms of action for antifungal agents on vital parameters of fungal cell structures were analyzed by using confocal laser scanning microscopy after staining samples with propidium iodide and acridine orange for 15 min to detect changes between intact and damaged cell surface. It was found that within the biofilm fungal cells preserved viability even after exposure to high concentrations of antifungals. In addition, despite the fungicidal drug activity at substantial concentrations acting on the biofilm cell membrane, the cell nuclei remained viable. Owing to the presence ot the mechanism of resistance in mycelial fungi shown in the study, it is necessary to take into account and investigate characteristics of biofilms in terms of drug sensitivity that will allow to optimize a choice of antimicrobial therapy.

Evolution of the complex treatment of purulent diseases of the hand including laser irradiation (a review)

Effects of 1270 nm laser light irradiation at phage particles of virulent klebsiellosis bacteriophage were studied. The medical klebsiellosis bacteriophage, manufactured industrially, was taken as the study object. Klebsiella pneumonia N 296, sensitive to the selected phage, was used as a test-culture. An experimental device manufactured by LTD «New surgical technologies» was used as a source of light. Semiconductor diodes generate light with wavelength 1270 nm (1268–1272 nm) in the continuous mode. The number of viable phage particles in the initial solution of klebsiellosis bacteriophage was 5×108. Irradiation of the phage with 1270 nm laser light decreased the number of viable phage particles to 105. Results did not practically depend on the exposure time, i. e. phage titers were equally reduced when exposed to laser light for 5 min, 10 min and 15 min. Irradiation of Klebsiella bacteriophage with 1270 nm laser light reduced the number of viable phage particles by 3 log orders (initial titer was 108; after irradiation – 105 negative phage colonies). It is indicative of their damage. Mechanisms of phage particle damage should be the object of further research so as to defi ne if laser irradiation with the above mentioned wavelengths can be used in medical practice.

STUDYING THE INFLUENCE OF PLASMA-CHEMICAL AND OZONE TREATMENT ON ARTIFICIALLY IMPLEMENTED MICROFLORA IN MODEL AQUEOUS SOLUTIONS

The pilot studies have been conducted to determine the biocidal effects of ozone and plasma chemical treatment for 1, 2, and 3 h on the strain “Moldavian” of infectious rhinotracheitis virus, reference strain of Escherichia coli ATCC 25922, atypical mycobacteria of the species Mycobacusleum phlei and archival strain of Aspergillus flavus artificially introduced into aqueous solution. It is shown that both treatments of aqueous solution contaminated with infectious rhinotracheitis virus have virucidal properties at the level of 95…100%. It was found that bactericidal (bacteriostatic) effect of ozone treatment for Escherichia coli fluid was 100% for all the time parameters. For plasma chemical treatment, the bacteriostatic effect (23%) was shown after the treatment within 3 h. The bactericidal (bacteriostatic) effect of ozone treatment for water samples contaminated with mycobacteria of the species M. phlei was only 65% at the treatment for 3 h. There was no bacteriostatic effect for plasma chemical treatment at any exposure. When studying the fungicidal (fungistatic) properties of ozone treatment for aqueous solution contaminated with a test culture of Aspergillus flavus, fungicidal properties were established (growth retardation by 95…98%). No fungicidal or fungistatic properties were shown for plasma chemical treatment.

The Use of Waste Sorbents for Surface Wastewater Treatment to Intensify Plant Growth

The possibility of using sorbents from FOPS® filters, spent in the processes of purification of surface wastewater, is shown to intensify the growth of radish plants of the “French breakfast” variety. The ability of these waste sorbents, introduced into soil-ground substrates (SGS) as structure-forming additives enriched with microelements, was found to significantly stimulate the development of the root system with some slight inhibition of shoot growth. In the course of the experiments, the optimal value of the addition of sorbents spent in the processes of cleaning surface runoff (from roads) to the SGS was determined, which provides the greatest increase in the biomass of the root system of plants used as a test culture. It has been established that the accumulation of heavy metals (HMs) in the leaves and roots of a plant test culture increases with an increase in their content in the spent sorbents, but the actual concentrations of HMs in plants do not exceed the standards for their content in robust feed for animal husbandry. An assessment was made of the use of sorbents spent in water purification processes to create soil used in the reclamation of landfills for the placement of solid municipal waste, industrial dumps, road slopes, as well as in the restoration of forest resources and soil remediation.

Impact of Biologically Active Complexes of L. rhamnosus GG and S. boulardii After Storage Under Low Temperatures on Biofilm Forming Ability in Corynebacteria

This paper describes the temperature regimens and shelf life of biologically active complexes (structural components and metabolites) of Lactobacillus rhamnosus GG and Saccharomyces boulardii, which have antimicrobial activity and reduce biofi lm formation in pathogenic agents of Corynebacterium spp. Preservation of biological activity of complexes after 6-month storage (observation period) at (−23 ± 1)°C and for 60 days (observation period) under hypothermia at (4 ± 1)°C has been demonstrated. The degree of inhibition of biofi lm formation in pathogenic corynebacteria depended on sensitivity of the Corynebacterium spp. test-culture strain to products of microbial origin. A mixture of lactobacillus and saccharomycete metabolites displayed weak biofi lm formation by toxicogenic strains of corynebacteria (p < 0.05). Our fi ndings testifi ed to a possible use of biologically active substances, stored at 4 and −23°C in designing the L. rhamnosus GG and S. boulardii complexes and in technological processes of their production to prevent the persistence of the diphtheria pathogens.

Antimicrobial activity of root canal filling materials

The antimicrobial activity of filling materials was studied to improve the quality of treatment of complicated caries in vitro. Resorcin-formalin cement Resodont (“Latus”, Ukraine) - № 1; Endocort zinc oxide-eugenol cement (“Latus”, Ukraine) - No. 2; materials based on zinc oxide eugenol cement with dexamethasone: Endomethasone ivory (Septodont, France) - No. 3 and Endofil ("Produit Dentaires SA", Switzerland) - No. 4. To assess the antimicrobial activity of the studied materials, test microorganism strains were used: Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 6783, Candida albicans ATCC 885-653. As a result of the study, it was established that filling materials have different antimicrobial activity. Resodont has the greatest antimicrobial activity on the test culture. Endomethason is active in relation to the test cultures studied, inferior to Resodont in its antimicrobial properties. Endocort and Endofil have less antimicrobial activity than Resodont and Endomethason, but have approximately equal growth retardation rates. It should be noted that with respect to Staphylococcus aureus, Endocort was found to be almost 1.5 times more active than Endofil. The conducted studies confirm that the materials for filling of root canals by Resodont and Endocort (Latus, Ukraine) have a pronounced antibacterial effect. They are competitive with foreign sealers and are the materials of choice, having a significantly lower cost.