Emmanuel Ndezure

Ghana

In Vitro Antimicrobial Activities of Vernonia amygdalina and Senna siamea Against ESBL-Producing and Non-ESBL Bacteria

Sumaila Mohammed1, Emmanuel Ndezure1*, Joseph Agyin1, Francisca Dery1, Ekua Amoah1, Kwadwo Boampong1

1. Kwame Nkrumah University of Science and Technology, Department of Theoretical and Applied Biology, Kumasi, Ghana

Abstract

Background

Antimicrobial resistance (AMR), particularly in extended-spectrum beta-lactamase (ESBL)-producing bacteria, presents a growing public health threat. This study investigated the antibacterial, synergistic, and antibiofilm activities of Vernonia amygdalina and Senna siamea leaf extracts against ESBL and non-ESBL strains of bacterial pathogens. The hypothesis was that these extracts contain phytochemicals with the capacity to inhibit resistant bacterial growth and biofilm formation.

Methods

Phytochemicals were screened using standard qualitative assays. Antibacterial activity was determined by agar well diffusion, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and synergy testing with ciprofloxacin using checkerboard assay to determine the Fractional Inhibitory Concentration index (FICi). Biofilm inhibition was assessed by crystal violet staining.

Results

Phytochemical screening identified alkaloids, flavonoids, tannins, saponins, glycosides, coumarins, triterpenoids, and phytosteroids in both extracts. Antimicrobial susceptibility testing showed that Vernonia amygdalina displayed moderate to strong activity, with inhibition zone diameters ranging from 15 mm (K. pneumoniae, weakest) to 21 mm (non-ESBL E. coli, strongest). Senna siamea exhibited consistently strong activity, with the highest inhibition zone of 28 mm against non-ESBL K. pneumoniae, followed by S. typhi (25 mm), S. aureus (23 mm), and E. coli (21 mm). ESBL strains were less susceptible but inhibited within 16–19 mm. MIC values ranged from 6.25–25 mg/mL (S. siamea) and 12.5–50 mg/mL (V. amygdalina). Both extracts showed synergy with ciprofloxacin (FICi ≤ 0.5), enhancing antibacterial effects, while biofilm inhibition reached 99.01% (V. amygdalina) and 99.72% (S. siamea) at 100 mg/mL.

Conclusions

Both extracts demonstrated strong antibacterial and antibiofilm activity, validating their potential as eco-friendly alternatives against resistant and biofilm-forming pathogens.