Antibacterial and Antibiofilm Activity of Ethanolic and Methanolic Nigella sativa L. Seed Extracts Against Pseudomonas aeruginosa ATCC 27853

ANTIBACTERIAL POTENTIAL OF MELIA AZEDARACH LEAVES AND FRUITS EXTRACTS AGAINST BACTERIAL SPECIES PRODUCING FOOD POISONING DISEASES

The current study was conducted for the evaluation of antimicrobial activities of Melia azedarach fruit and leaf extracts using aqueous and ethanol solvents against 5 bacterial strains: Pseudomonas aeruginosa, Salmonella typhi, Staphylococcus aureus, Escherichia coli, and Bacillus cereus. Antibacterial activities were evaluated by the disc diffusion method, whereas the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were measured applying standards bacteriological techniques. Outcomes of the disc diffusion technique assay showed that ethanol extracts displayed significant antibacterial potential as compared with water extracts, with a zone of inhibition spectrum of 15 to 22 mm for fruits and leaves, matched to 10 to 14 mm for water extracts at 100 mg/mL. The maximum vulnerability was shown against Bacillus cereus, while Pseudomonas aeruginosa showed the smallest sensitivity. The MIC degree additionally verified strong efficiency of ethanol leaf extracts, ranging from 25 to 125mg/mL, whereas fruit extracts (aqueous) showed the maximum MIC degrees (up to 200mg/mL). Likewise, MBC results showed that ethanol leaf extracts had the strongest bactericidal efficiency (50–225 mg/mL), while fruit water extracts displayed the weakest activities (200–250 mg/mL). Generally, the results indicate that Melia azedarach exhibits strong antibacterial activities, predominantly in ethanol leaf extracts, and might act as a latent source of natural antibacterial substances. The research also highlights the dissimilarity in microbial vulnerability, with Gram-positive microbes being more susceptible as compared with Gram-negative microbes.

Preliminary Evaluation of the Antibacterial Activity of an Ethanolic Extract from Commercial Chlorella vulgaris Powder Against Two Reference Bacterial Strains

Antibiotic resistance is a growing clinical challenge, particularly among Klebsiella pneumoniae and Staphylococcus aureus, prompting interest in natural antimicrobial agents such as microalgae. To evaluate the in vitro antibacterial activity of an ethanolic extract prepared from commercial Chlorella vulgaris powder against reference strains of K. pneumoniae (ATCC 13883) and S. aureus (ATCC 25923). Three extract concentrations (100, 50, and 10 mg/mL) were tested using the disk diffusion method alongside standard antibiotics, in triplicate. Total inhibition diameters were recorded, and the 6 mm disk diameter was subtracted to obtain net inhibition zones. Data were analysed by two-way ANOVA with Tukey's HSD post-hoc test. Treatment significantly affected inhibition zone size (F(6,28) = 262.58, P < 0.001), while bacterial species alone had no significant effect (P = 0.456) and the treatment × species interaction was not significant (P = 0.114). A dose-dependent increase was observed; at 100 mg/mL, mean net inhibition zones reached 12.33 ± 2.52 mm for K. pneumoniae and 10.33 ± 1.53 mm for S. aureus. The ethanolic extract of commercial C. vulgaris powder exhibited detectable, dose-dependent antibacterial activity against both reference strains, warranting further MIC, MBC, and chemical characterisation studies.

Evaluation of antibacterial and antibiofilm activity of Lacticaseibacillus sp. KJK14S1 strain isolated from unexplored region of Indian Sundarbans against Gram-negative bacteria

In vitro antibacterial activity of selected medicinal plant extracts against Escherichia coli in Adami Tulu Jiddo Kombolcha district, Ethiopia

The increasing prevalence of antimicrobial-resistant Escherichia coli necessitates the exploration of alternative antimicrobial agents from botanical sources. Objective: This study evaluated the in vitro antibacterial activity of methanolic and ethanolic leaf extracts of Datura stramonium , Balanites aegyptiaca , and Acokanthera schimperi against field and reference strains of E. coli . Methods: Following phytochemical screening, antibacterial activity was determined using the disk diffusion method, while Minimum Inhibitory Concentrations (MIC) and Minimum Bactericidal Concentrations (MBC) were determined using the broth dilution method. Results: All extracts demonstrated concentration-dependent inhibitory effects. The methanolic extract of D. stramonium (100 mg/mL) exhibited the highest antibacterial activity, producing a zone of inhibition of 20.27 ± 0.37 mm against the field isolate. This inhibition zone was similar to that of the ciprofloxacin positive control (19.7 ± 0.3 mm). Methanol consistently demonstrated higher extraction yield and antibacterial activity than ethanol across most tested species. D. stramonium and A. schimperi showed MIC values as low as 0.78 mg/mL, while all extracts exhibited bactericidal activity based on an MBC/MIC ratio of 2. Conclusion: These findings support the potential of the selected medicinal plants as sources of antibacterial compounds and provide a basis for further investigations involving bioactive compound characterization, safety assessment, and in vivo validation.

Antibacterial Activity of Imperata cylindrica Root Fractions against Pathogenic Bacteria

Antibiotic resistance has increased the need for new antibacterial agents from natural sources. This study evaluated the antibacterial activity of ethanolic root extract fractions of Imperata cylindrica against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Root powder was extracted with 70% ethanol and sequentially fractionated using n-hexane, ethyl acetate, n-butanol, and distilled water. Antibacterial activity was determined by the disk diffusion method at concentrations of 62.5–500 mg/mL. The most active fraction was further analyzed using thin-layer chromatography and silica gel column chromatography. The n-butanol fraction exhibited the strongest antibacterial activity, producing inhibition zones of 11.50, 9.00, and 8.17 mm against S. aureus, E. coli, and P. aeruginosa, respectively, at 500 mg/mL. Column chromatography generated 92 vials that were combined into nine subfractions. These findings indicate that the n-butanol fraction is a promising source of antibacterial compounds for further isolation and characterization.

Antibiofilm potential of biogenic magnesium oxide nanoparticles against multidrug resistant gram-negative bacteria.

It is suggested that biogenically synthesized MgO NPs hold considerable promise as antibacterial and antibiofilm agents against MDR Gram-negative pathogens.