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Description
Antimicrobial resistance, particularly in extended-spectrum beta-lactamase (ESBL)-producing bacteria, poses a major health challenge. This study asked: Do extracts of Vernonia amygdalina and Senna siamea exhibit antibacterial, antibiofilm, and synergistic activities against ESBL-producing and other pathogenic bacteria?
Objectives: To determine phytochemical composition, antibacterial potency, synergy with ciprofloxacin, and antibiofilm activity of the extracts against Staphylococcus aureus, Salmonella enterica serovar Typhi, Escherichia coli, and Klebsiella pneumoniae.
Methodology: Phytochemicals were screened by standard assays. Antibacterial activity was determined using agar well diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) tests. Synergy with ciprofloxacin was evaluated by MIC fold reduction. Biofilm eradication was measured by crystal violet staining on pre-formed biofilms to assess disruption.
Key findings: Vernonia amygdalina contained alkaloids, saponins, flavonoids, tannins, coumarins, triterpenoids, phytosteroids, and cardiac glycosides, while Senna siamea lacked cardiac glycosides. Among the extracts, S. siamea exhibited the strongest antibacterial effect with the highest inhibition zone (27.83 ± 3.87 mm against K. pneumoniae), whereas V. amygdalina produced 21.33 ± 4.45 mm against E. coli. MIC values ranged from 6.25 ± 0.00–33.33 ± 14.43 mg/mL for S. siamea and 12.5 ± 0.00–50.00 ± 0.00 mg/mL for V. amygdalina. Synergy testing with sub-inhibitory ciprofloxacin revealed marked modulation of extract activity, with up to a 64-fold MIC reduction for S. siamea against ESBL E. coli and an 8-fold reduction for V. amygdalina against ESBL K. pneumoniae. Extract–extract modulation showed S. siamea reduced V. amygdalina’s highest MIC by 8-fold against non-ESBL E. coli, while V. amygdalina reduced S. siamea’s MIC up to 4-fold. Both extracts inhibited biofilm formation dose-dependently, achieving >99% inhibition at 100 mg/mL.
Implications: These results demonstrate strong antibacterial, synergistic, and antibiofilm activities, supporting V. amygdalina and S. siamea as potential eco-friendly alternatives against resistant and other pathogenic bacteria.
Preferred presentation: Oral
Subtheme: Health Systems, Basic Sciences, Biomedical Advances, Pharmaceutical Sciences and Human Wellbeing