In vitro combinational efficacy of ceftriaxone and leaf extract of Combretum albidum G. Don against multidrug-resistant Pseudomonas aeruginosa and host-toxicity testing with lymphocytes from human cord blood

Valorization of oil refinery by-products: production of sophorolipids utilizing fatty acid distillates and their potential antibacterial, anti-biofilm, and antifungal activities

Starmerella bombicola is a native yeast strain producing sophorolipids as secondary metabolites. This study explores the production, characterization, and biological activities of sophorolipids and investigates the antimicrobial, anti-biofilm, and antifungal properties of sophorolipids produced from oil refinery wastes by the yeast Starmerella bombicola. The present work demonstrated that S. bombicola MTCC 1910 when grown in oil refinery wastes namely palm fatty acid distillates and soy fatty acid distillates enhanced the rate of sophorolipids production drastically in comparison to vegetable oil, sunflower oil used as hydrophobic feedstock. Sophorolipid yields were 18.14, 37.21, and 46.1 g/L with sunflower oil, palm, and soy fatty acid distillates respectively. The crude biosurfactants were characterized using TLC, FTIR, and HPLC revealing to be acetylated sophorolipids containing both the acidic and lactonic isomeric forms. The surface lowering and emulsifying properties of the sophorolipids from refinery wastes were significantly higher than the sunflower oil-derived sophorolipids. Also, all the sophorolipids exhibited strong antibacterial properties (minimum inhibitory concentrations were between 50 and 200 µg mL-1) against Salmonella typhimurium, Bacillus cereus, and Staphylococcus epidermidis and were validated with morphological analysis by Scanning electron microscopy. All the sophorolipids were potent biofilm inhibitors and eradicators (minimum biofilm inhibitory and eradication concentrations were between 12.5 to 1000 µg mL-1) for all the tested organisms. Furthermore, antifungal activities were also found to exhibit about 16-56% inhibition at 1 mg mL-1 for fungal mycelial growth. Therefore, this endeavour of sophorolipids production using palm and soy fatty acid distillates not only opens up a window for the bioconversion of industrial wastes into productive biosurfactants but also concludes that sophorolipids from oil refinery wastes are potent antimicrobial, anti-biofilm, and antifungal agents, highlighting their potential in biotechnological and medical applications.

Investigation of genetic toxicity and oxidative stress of Clostridium perfringens epsilon toxin type D on human peripheral blood lymphocytes

Epsilon toxin (Etx) is an enormously potent pore-forming toxin and a category B biological agent. Etx is the main virulence determinant of Clostridiumperfringens types B and D toxin. It has a cytotoxic effect on distal and collecting kidney tubules. Also, Etx crosses the blood-brain barrier, binds to myelin structures, and destroys oligodendrocytes. The main purpose of this study was to investigate the toxic effects of Etx on human blood lymphocytes, which we examined for the first time for the genetic toxicity of this bacterial toxin. In this study, after taking blood and dividing into nine groups and putting in contact with different dilutions of Etx (1,5,10,25,50,100 and 200 μM), methotrexate (750 μM), and normal saline by Cytokinesis blocked micronucleus (CBMN) assay, we looked at genetic toxicity and the level of oxidative stress created in the under study lymphocytes. The results of this study showed that Etx has significant oxidative stress effects on human lymphocytes at doses above 25 μM, and also this bacterial toxin significantly increases the number of micronuclei formed in lymphocytes. The results of this study indicate that Etx has toxic effects it is genetic and interferes with cell division processes. Thus, human lymphocytes can be used extensively in future studies on Etx.

Inhibition of New Delhi Metallo-β-Lactamase 1 (NDM-1) Producing Escherichia coli IR-6 by Selected Plant Extracts and Their Synergistic Actions with Antibiotics

Improper use of antibiotics has led to a great concern in the development of pathogenic microbial resistance. New Delhi metallo-β-lactamase 1 (NDM-1) producing bacteria are resistant to most of the β-lactam antibiotics, and so far, no new compounds have been clinically tested against these bacteria. In this study, ethanol extracts from the leaves of 240 medicinal plant species were screened for antibacterial activity against an NDM-1 Escherichia coli strain. The extracts that showed antibacterial activity were then tested for minimum inhibitory concentrations (MICs) and zones of inhibition. The extract from Combretum albidum G. Don, Hibiscus acetosella Welw. ex Hiern, Hibiscus cannabinus L., Hibiscus furcatus Willd., Punica granatum L., and Tamarindus indica L. showed bactericidal activity between 5 and 15 mg/ml and the MIC was between 2.56 and 5.12 mg/ml. All six plant extracts inhibited activity of the NDM-1 enzyme in vitro, and the IC50 value ranged between 0.50 and 1.2 ng/μl. Disruption of bacterial cell wall integrity by the plant extracts was clearly visible with scanning electron microscopy. Increases in membrane permeability caused 79.4–89.7% bacterial cell deaths as investigated by fluorescence-activated cell sorting. All the plant extracts showed synergistic effects when combined with colistin [fractional inhibitory concentration (ΣFIC) = 0.125–0.375], meropenem (ΣFIC = 0.09–0.313), and tetracycline (ΣFIC = 0.125–0.313). Thus, the plant extracts can be fractionated for the identification of active compounds, which could be used as new antibacterial compounds for the development of drugs against NDM-1 E. coli in addition to their use in combination therapy.

In vitro Antibacterial Activity of Combretum edwardsii, Combretum krausii, and Maytenus nemorosa and Their Synergistic Effects in Combination with Antibiotics

The study investigated the antibacterial activity of crude extracts of C. edwardsii, Combretum krausii, and Maytenus nemorosa as well as their interactions with selected antibiotics against drug resistant bacterial strains. Using the rapid p-iodonitrotetrazolium chloride colorimetric assay, minimum inhibitory concentration values of plant extracts and antibiotics were determined. The interactions of plant extracts and antibiotics were studied using a checkerboard method. The MICs of the plant extracts and antibiotics were in the range of 0.037–6.25 and 0.001–2.5 mg/ml, respectively. The plant fractions tested in the present study displayed varying levels of antibacterial activity depending on the bacterial strains. Generally, Staphylococcus aureus was the most susceptible of the three strains of bacteria while the other two beta-lactamase producing Gram-negative bacteria were the most resistant. The hexane leaf extract of M. nemorosa was the most active (MIC = 37 μg/ml) against S. aureus. Ethyl acetate leaf extract of C. krausii was the most active against Klebsiella pneumoniae and ethyl acetate leaf extract of C. edwardsii was the most active against Escherichia coli. Synergistic interactions were detected in 13% of the combinations against E. coli, 27% of the combinations against K. pneumoniae and 80% of the combinations against S. aureus. The few synergistic interactions observed in the present study suggest that the crude extracts of the leaves of M. nemorosa, C. edwardsii, and C. krausii could be potential sources of broad spectrum antibiotic resistance modifying compounds.

In silico attempt for adduct agent(s) against malaria: Combination of chloroquine with alkaloids of Adhatoda vasica

With the aim of controlling drug resistant Plasmodium falciparum, a computational attempt of designing novel adduct antimalarial drugs through the molecular docking method of combining chloroquine with five alkaloids, individually is presented. These alkaloids were obtained from the medicinal plant, Adhatoda vasica. From the obtained individual docking values of important derivatives of quinine and chloroquine, as well as, individual alkaloids and adduct agents of chloroquine with Adhatoda alkaloids as ligands, it was discernible that the 'adduct agent-1 with chloroquine and adhatodine' combination had the minimum energy of interaction, as the docking score value of -11.144 kcal/mol against the target protein, triosephosphate isomerase (TIM), the key enzyme of glycolytic pathway. Drug resistance of P. falciparum is due to a mutation in the polypeptide of TIM. Moratorium of mutant TIM would disrupt the metabolism during the control of the drug resistant P. falciparum. This in silico work helped to locate the 'adduct agent-1 with chloroquine and adhatodine', which could be taken up by pharmacology for further development of this compound as a new drug against drug resistant Plasmodium.

In Vitro Antibacterial Activity, Gas Chromatography-Mass Spectrometry Analysis of Woodfordia fruticosa Kurz. Leaf Extract and Host Toxicity Testing With In Vitro Cultured Lymphocytes From Human Umbilical Cord Blood

Objectives

To locate a plant with suitable phytochemicals for use as antimicrobial agents to control multidrug-resistant (MDR) bacteria as a complementary medicine, without host toxicity as monitored through cultured lymphocytes from human umbilical cord blood.

Methods

The methanol crude leaf extract of the plant Woodfordia fruticosa was subjected to antimicrobial assay in vitro with nine pathogenic MDR bacteria from clinical samples. This was followed by bioassay-guided fractionation with seven non-polar to polar solvents, gas chromatography–mass spectrometry analysis of the n-butanol fraction, and monitoring of the host toxicity of the leaf extract with in vitro grown lymphocytes from human umbilical cord blood.

Results

The leaf extract of W. fruticosa had a controlling capacity for MDR bacteria. The minimum inhibitory concentration and minimum bactericidal concentration of the n-butanol fraction were < 1.89 mg/mL extract and 9.63 mg/mL extract, respectively. The gas chromatography–mass spectrometry spectrum of the n-butanol fraction confirmed the presence of 13 peaks of different compounds with retention times of 9.11 minutes, 9.72 minutes, 10.13 minutes, 10.78 minutes, 12.37 minutes, 12.93 minutes, 18.16 minutes, 21.74 minutes, 21.84 minutes, 5.96 minutes, 12.93 minutes, 24.70 minutes, and 25.76 minutes. The six leading compounds were: diethyl phthalate: IUPAC name: diethyl benzene-1,2-dicarboxylate; 5-methyl-2-(1-methylethyl) phenol: IUPAC name: 5-methyl-2-propan-2-ylphenol; (E )-3,7-dimethylocta-2,6-diene-1-thiol: IUPAC name: (2Z)-3,7-dimethylocta-2,6-diene-1-thiol; 2,6,10-dodecatrien-1-ol, 3,7,11-trimethyl-, (E,E ): IUPAC name: 2,6,10-dodecatrien-1-ol; 3,7,11-trimethyl-, (E,E); 2-methoxy-4-(2-propenyl) phenol: IUPAC name: 2-methoxy-4-[(1E)-prop-1-en-1-yl]phenol; hexadecanoic acid: IUPAC name: hexadecanoic acid.

Conclusion

The presence of antimicrobial compounds that are therapeutically potent against MDR bacteria was confirmed in W. fruticosa. The crude leaf extract showed no host toxicity with human lymphocytes; the n-butanol fraction of the extract was the most suitable bioactive fraction. The terpenes isolated were: 5-methyl-2-(1-methylethyl) phenol, 2-methoxy-4-(2-propenyl) phenol, 2,6-octadien-1-ol, 3,7-dimethyl-(E)-2,6-octadienal, 3,7-dimethylcyclohexanol, and cyclohexanol, 2-methylene-5-(1-methylethenyl) which were reported to have specifically antimicrobial activity.

Monitoring in vitro antibacterial efficacy of 26 Indian spices against multidrug resistant urinary tract infecting bacteria

BACKGROUND

To screen methanolic extracts of 26 commonly used Indian spices against nine species of uropathogenic bacteria (Enterococcus faecalis, Staphylococcus aureus, Acinetobacter baumannii, Citrobacter freundii, Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Pseudomonas aeruginosa), isolated from clinical samples of a tertiary care hospital for antibacterial activity.

METHODS

Bacterial strains were subjected to antibiotic sensitivity testing by Kirby-Bauer's disc diffusion method. Monitoring antibacterial potentiality of spice extracts was done by the agar-well diffusion method with multidrug resistant (MDR) strains of nine uropathogens.

RESULTS

The Gram-positive (GP) bacteria E. faecalis and S. aureus were resistant to 16 of the 21 antibiotics used. Among the Gram-negative (GN) bacteria, resistant patterns were A. baumannii and E. aerogenes to 12, C. freundii to 14, E. coli to 12, K. pneumoniae to 10, P. mirabilis to 11, and P. aeruginosa to 15 antibiotics of the 18 antibiotics used. The most effective 15 spices, having at least 25-29 mm as the size of the zone of inhibition, were Allium cepa, Brassica juncea, Cinnamomum tamala, Cinnamomum zeylanicum, Coriandrum sativum, Cuminum cyminum, Curcuma longa, Mentha spicata, Murraya koenigii, Nigella sativa, Papaver somniferum, Piper nigrum, S. aromaticum, Trachyspermum ammi, and Trigonella foenum for at least one of the GP or GN MDR bacterial strains used. Moderate control capacity was registered by nine spices, Curcuma amada, Foeniculum vulgare, Illicium verum, Mentha spicata, Papaver somniferum, Syzygium aromaticum, Trachyspermum ammi, Trigonella foenum, and Zingiber officinale. However, the best two spices for controlling all the pathogens used were C. zeylanicum and C. longa, with the highest value of 29 mm as the inhibition zone size.

CONCLUSION

The most effective and unique 16 spice plants recorded for the in vitro control of MDR uropathogens could further be pursued for the development of complementary and supplementary medicine against MDR bacteria.