Isolation of rare Genera of actinomycetes — antibiotic producers from soils using Aloe Arborescens juice

The search for new antibiotics is an urgent problem due to the spread of resistance to existing antibacterial drugs in pathogenic microorganisms. Actinomycetes are producers of a large number of antibiotics used in medicine. Most antibiotics are isolated from actinomycetes of the Streptomyces genus, while rare genera of actinomycetes can be the producers of new antibiotics.The aim of the study is to investigate the effect of the biological substances complex present in aloe juice on the growth stimulation of rare genera of actinomycetes.Material and methods. Objects: samples of sod-podzolic soil and chernozem. The standard method of sowing soil suspensions on oat agar and Gause medium No. 2 was used to isolate actinomycetes. Chemotaxonomic properties were determined using the methods of ascending thin-layer chromatography on a cellulose layer. The generic identity of cultures was determined using Bergey’s manual and materials comparing the composition of cell walls of actinobacteria. DNA PCR with standard 27f and 1492r primers, as well as Sanger sequencing, were performed to study genosystematic features. Antibiotic activity was determined against the test microorganisms: Staphylococcus aureus ИНА 00985 (FDA 209P), Staphylococcus aureus ИНА 00761 (MRSA), Staphylococcus aureus ИНА 00762 (УФ- 2), Micrococcus luteus ATCC 9341, Bacillus subtilis ATCC 6633, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Saccharomyces cerevisiae ИНА 01042.Results. A total of 527 actinomycete cultures were isolated from samples of sod-podzolic soil and chernozem with the addition of aloe juice; their phylogenetic position was determined. The dominant actinomycetes in the studied soil samples are the representatives of the genus Streptomyces. Bacteria of the genus Micromonospora take the second place by the number of isolated cultures. Rare genera of actinomycetes have also been identified: Nonomuraea, Streptosporangium, Nocardia, Actinomadura, Actinocorallia, Pseudonocardia, Amycolatopsis, Saccharomonospora, Saccharopolyspora, Promicromonospora, Kribbella. It was determined that the isolated cultures possess antibiotic activity against test microorganisms.Conclusion. It is advisable to use aloe juice after subjecting the leaves to biostimulation to isolate actinomycetes from the soil and identify their biodiversity.

SECONDARY METABOLITES WITH ANTIBIOTIC ACTIVITY OF MARINE ACTINOBACTERIA

Marine actinobacteria are active producers and an unused rich source of various biologically active secondary metabolites, such as antibiotics, antitumor, antiviral and antiinflammatory compounds, biopesticides, plant growth hormones, pigments, enzymes, enzyme inhibitors.In this review describes data from current literature sources for the period from 2017 to 2021 about various bioactive compounds that produce marine actinobacteria, their antibiotic activity and biotechnological potential, the main groups of secondary metabolites and their producers.

Evaluation of the Use of Antibiofilmogram Technology in the Clinical Evolution of Foot Ulcers Infected by Staphylococcus aureus in Persons Living with Diabetes: A Pilot Study

Infected diabetic foot ulcers (DFUs) represent a serious threat to public health because of their frequency and the severity of their consequences. DFUs are frequently infected by bacteria in biofilms, obstructing antibiotic action. Antibiofilmogram was developed to assess the impact of antibiotics to inhibit biofilm formation. This pilot study aimed to determine the benefits of this technology in predicting antibiotic activity on the outcome of 28 patients with Grade 2 DFUs that were infected by a monomicrobial Staphylococcus aureus. Patients with diabetes were followed during the antibiotic treatment (day 14) and the follow-up period of the study (day 45). The contribution of Antibiofilmogram was compared between patients with non-concordant results (n = 13) between antibiogram and Antibiofilmogram versus concordant results (n = 15). The clinical improvement of wounds (80.0% vs. 38.5%, p = 0.0245) and the absence of exudates (0% vs. 33.3%, p = 0.0282) were observed in concordant vs. discordant groups. This pilot study provides promising results for the interest of Antibiofilmogram in the prescription of antibiotics to prevent biofilm formation in infected DFUs.

Antibiotic Activity of Actinomycetes Isolated from Young Tectona Grandis (L.) Wood and Pith

Actinomycetes are a source for novel bioactive compounds and justify obtaining new species from various sources. Hardwoods such as Tectona grandis (L.) have not been studied for actinomycete isolation. We aim to isolate endophytic actinomycetes from young Tectona grandis wood and pith and screen for antibiotic activity. Five young wood were cut and surface sterilized using ethanol and hypochlorous acid. The wood and pith of each sample are placed in eight plates of Humic acid-vitamin B (HV), Tap water Yeast extract (TWYE), and Yeast Extract Casein Digest (YECD) medium and incubated at 27°C for four weeks. Actinomycetes were isolated from such medium, observed every week, and transferred to an International Streptomyces Project-2 (ISP-2) medium for identification and antibiotic production tested against Staphylococcus aureus, Helicobacter pylori, and Escherichia coli using the Kirby-Bauer method. Seven actinomycetes were isolated from the wood, primarily from YECD and TWYE media, with varying morphological characteristics. One isolate having maroon-colored aerial and vegetative mycelium with grey spores showed moderate antibacterial activity against S. aureus and H. pylori (13.49±1.03 mm and 14.9±0.7 mm, respectively), while two other actinomycetes showed weak activity against these bacteria. However, none of the actinomycetes show any activity against E. coli. Tectona grandis (L.) is a potential source for novel actinomycetes with an antibiotic activity which warrants further exploration

Enhancement of Antibiotic Activity by 1,8-Naphthyridine Derivatives against Multi-Resistant Bacterial Strains

The search for new antibacterial agents has become urgent due to the exponential growth of bacterial resistance to antibiotics. Nitrogen-containing heterocycles such as 1,8-naphthyridine derivatives have been shown to have excellent antimicrobial properties. Therefore, the purpose of this study was to evaluate the antibacterial and antibiotic-modulating activities of 1,8-naphthyridine derivatives against multi-resistant bacterial strains. The broth microdilution method was used to determine the minimum inhibitory concentration (MIC) of the following compounds: 7-acetamido-1,8-naphthyridin-4(1H)-one and 3-trifluoromethyl-N-(5-chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide. The antibiotic-modulating activity was analyzed using subinhibitory concentrations (MIC/8) of these compounds in combination with norfloxacin, ofloxacin, and lomefloxacin. Multi-resistant strains of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were used in both tests. Although the compounds had no direct antibacterial activity (MIC ≥ 1.024 µg/mL), they could decrease the MIC of these fluoroquinolones, indicating synergism was obtained from the association of the compounds. These results suggest the existence of a structure–activity relationship in this group of compounds with regard to the modulation of antibiotic activity. Therefore, we conclude that 1,8-naphthyridine derivatives potentiate the activity of fluoroquinolone antibiotics against multi-resistant bacterial strains, and thereby interesting candidates for the development of drugs against bacterial infections caused by multidrug resistant strains.

Approach to Searching for the Producers of Antibiotics That Overcome Drug Resistance of Microorganisms

Currently, the problem of antibiotic resistance of opportunistic and pathogenic microorganisms is extremely urgent. In order to find new effective natural antibiotics, it is necessary to intensify the search process. In the gradual selection of the most promising producers, we introduced the stage of determining the antibiotic activity of the culture fluid of the studied natural strains against the clinical isolates of hospital microorganisms with multiple resistance to medical antibiotics. Determining the species affiliation of potential producers allows to select those producers of a particular species that differ in the antimicrobial spectrum of activity from those described in the literature. Four strains of actinomycetes that showed activity against resistant clinical isolates of yeast Candida albicans, C.famata, C.parapsilosis and Cryptococcus neoformans were selected, namely: Nocardia soli INA 01217, Streptomyces bottropensis INA 01214, S.chromofuscus INA 01211 and S.netropsis INA 01190. The N.soli INA 01217 strain also shows antibiotic activity against the Gram-negative bacterium Escherichia coli ATCC 25922. These strains of actinobacterial producers were selected for subsequent chemical studies of the antimicrobial compounds formed by them.

Ring D-Modified and Highly Reduced Angucyclinones From Marine Sediment-Derived Streptomyces sp.

Angucyclines and angucyclinones represent the largest family of type II PKS-engineered natural products. Chemical analysis of a marine Streptomyces sp. KCB-132 yielded three new members, actetrophenone A (1) and actetrophenols A–B (2–3). Their structures were elucidated by NMR spectroscopy, X-ray crystallography and CD calculations. Actetrophenone A (1) is the first representative of a novel-type angucyclinone bearing a nonaromatic D-ring. Actetrophenol A (2) features a highly reduced and aromatized four-ring system, which is unprecedented for natural products. While (Ra)- and (Sa)-actetrophenol B (3) bear an unprecedented N-acetyltryptamine-substituted tetraphene core skeleton, this is the first report of a pair of atropisomeric isomers in the angucyclinone family. Actetrophenol A (2) exhibits remarkable antibiotic activity, notably including potent activity to multiple resistant Staphylococcus aureus and Enterococcus faecium with MIC values of 4 μg/ml, in contrast, the positive control antimicrobial agent penicillin was inactive up to 32 μg/ml.