Urinary tract infections (UTIs) are common bacterial infections. The global emergence of multidrug-resistant uropathogens in the last decade underlines the need to search for new antibiotics with novel mechanisms of action. In this regard, exploring endophytic fungi inhabiting medicinal plants used locally against urinary tract infections could be a promising strategy for novel drug discovery. This study investigates crude metabolites from endophytic fungi isolated from Annona muricata as potential sources of antibiotic drugs to fight against uropathogens and reduce related oxidative stress. Crude ethyl acetate extracts from 41 different endophytic fungi were screened against three bacterial strains using the broth microdilution method, and fungi producing active crude extracts were identified using ITS1-5.8S rRNA-ITS2 nucleotide sequences. The antibacterial modes of action of the five most active extracts were evaluated using Staphylococcus aureus ATCC 43300 and Klebsiella oxytoca strains. The DPPH and FRAP assays were used to investigate their antioxidant activity, and their cytotoxicity against the Vero cell line was evaluated using the MTT assay. Out of the 41 crude extracts tested, 17 were active with minimum inhibitory concentrations (MICs) ranging from 3.125 μg/mL to 100 μg/mL and were not cytotoxic against Vero cell lines with a cytotoxic concentration 50 (CC50) >100 μg/mL. The more potent extracts (from Fusarium waltergamsii AMtw3, Aspergillus sp. AMtf15, Penicillium citrinum AMf6, Curvularia sp. AMf4, and Talaromyces annesophieae AMsb23) significantly inhibited bacterial catalase activity, lysed bacterial cells, increased outer membrane permeability, and inhibited biofilm formation, and the time-kill kinetic assay revealed concentration-dependent bactericidal activity. All seventeen extracts showed weak ferric iron-reducing power (1.06 to 12.37 μg equivalent NH2OH/g of extract). In comparison, seven extracts exhibited DPPH free radical scavenging activity, with RSA50 ranging from 146.05 to 799.75 μg/mL. The molecular identification of the seventeen active fungi revealed that they belong to six distinct genera, including Aspergillus, Curvularia, Fusarium, Meyerozyma, Penicillium, and Talaromyces. This investigation demonstrated that fungal endophytes from Cameroonian Annona muricata, a medicinal plant used locally to treat bacterial infections, might contain potent antibacterial metabolites with multiple modes of action. The antibacterial-guided fractionation of these active extracts is currently ongoing to purify and characterise potential antibacterial active ingredients. 

Crude metabolites from endophytic fungi inhabiting Cameroonian Annona muricata inhibit the causative agents of urinary tract infections

Antibacterial effect of the ethanol, methanol and ethyl acetate extracts of Piliostigma reticulatum and Cleistopholis patens on ten pathogenic bacteria including Pseudomonas aeruginosa, Salmonella typhi, Escherichia coli, Proteus vulgaris, Streptococcus pyogenes, Klebsiella aerogenes, Staphylococcus aureus, Serratia marscences, Yersinia enterocolitica and Shigella dysenteriae was investigated.  Survival rate after treatment was investigated. Cell surface hydrophobicity after treatment was tested and the catalase activities of the plant extracts were determined. The results revealed that at 100mg/ml of extracts, the ethanol  extracts of C. patens  showed antibacterial activities against S. typhi, P. vulgaris, Str. pyogenes, K. aerogenes, Saureus and Yersinia enterocolitica with zones of inhibition of 18mm, 14mm, 18mm, 24mm, 14mm and 18mm respectively and the ethyl acetate extract  was active against Sal. typhi,  P. vulgaris, Str. pyogenes, K. aerogenes,  S. aureus Ser. marscences and Y. enterocolitica with zones of inhibition of 14mm, 22mm, 18mm, 18mm, 14mm, 16mm and 16mm respectively while ethanol extract of P. reticulatum showed activity against P. aeruginosa, Sal. typhi, E.coli, Str. pyogenes, K. aerogenes, S. aureus, and Sh. dysenteriae with zones of inhibition of 13mm, 12mm, 10mm, 10mm, 8mm, 10mm and 14mm respectively. The ethyl acetate was active against E.coli, Str. pyogenes, K. aerogenes, S. aureus and Sh. dysenteriae respectively.  The methanol extract had no activity against the test organisms. The kill- time curve showed that susceptible cells die after 10 and 20minutes after contact with the extracts of C. patens for most of the test bacteria while cell death occurred at 10, 20, 40, 50 and 60 min after contact. The hydrophobicity test showed that test organisms had hydrophobicity of between 47% and 99% in the extracts. Catalase production reduced considerably in some bacteria after treatment with plant extracts. The results obtained presupposes that the plant extracts are effective against some of the test organisms and their mode of activity are is that they interfere with the ability of bacteria to produce catalase,  inducing cell death by the production of hydroxyl radical and  also by to the enhancement of non-opsonic phagocytosis of bacteria by macrophages.

https://ejbio.org/index.php/ejbio/article/download/18/9

Catalase Activity and Hydrophobicity Test of Bacteria Susceptible to Extracts of Cleistopholis Patens and Piliostigma Reticulatum

Citation: Bolaji Samuel; The comparative antibacterial effect of aqueous extract of Carica papaya leaves and Carica papaya nanoparticles against selected bacteria; Cyber Security 2020; May 21, 2020; London, UK International Conference on Ethicalhacking and Cybersecurity | May 21, 2020 | London, UK Abstract: Silver salt and its colloidal formulations have been used since ancient times to treat ulcers, burns chronic wounds and other infections but its use was discontinued due to the interfering effects of salt and the development of new antibiotics, However, almost a decade back, renew interest grew for nanosilver owing to its high surface area to volume ratio and size-dependent unique optical, electrical, and thermal properties. Silver nanoparticles were synthesized using eco-friendly method with extract of Carica papaya as reducing and stabilizing agent. The silver nitrate solution was used as precursor. A visible colour change from yellow to dark brown confirmed the formation of the nanoparticles and the UV-Vis spectroscopy showed an absorbance of 0.69 at wavelength 435 nm for the silver nanoparticle. The antimicrobial activity of the synthesized nanoparticles was studied against Escherichia coli, Salmonella typhi and Staphylococcus aureus. The silver nanoparticles biosynthesized showed antimicrobial activity against the test isolates with zone of inhibition ranging from 10-15mm. Antimicrobial activity of silver nanoparticles was statistically significant as compared to Chloramphenicol at 0.05% level of confidence. Generally, the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values for Silver nanoparticle ranged from 0.22 – 0.42 g/ml and 1 – 30 cfu/ml respectively, against the test organisms. S. aureus was most sensitive while E. coli and S. typhi were least sensitive to silver nanoparticles, while the activities of C. papaya extract ranged from 0.32 – 0.42 g/ml and 6 – 36 cfu/ml respectively, against the test organisms E. coli and S. aureus were more sensitive while S. typhi was least sensitive to C. papaya nanoparticles.

/pdf/the-comparative-antibacterial-effect-of-aqueous-extract-of-2kdkoh6z1k.pdf

The comparative antibacterial effect of aqueous extract of Carica papaya leaves and Carica papaya nanoparticles against selected bacteria

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Catalase Activity and Hydrophobicity Test of Bacteria Susceptible to Extracts of Cleistopholis Patens and Piliostigma Reticulatum

The comparative antibacterial effect of aqueous extract of Carica papaya leaves and Carica papaya nanoparticles against selected bacteria