Monitoring in vitro antibacterial efficacy of Terminalia alata Heyne ex. Roth, against MDR enteropathogenic bacteria isolated from clinical samples

Abstract

The employed antibiotic could be ineffective against acute health effect causing multidrug resistant enteropathogenic bacteria. Thus, phytodrugs could be used for its control. Leaf and bark extracts of Terminalia alata, an ethnomedicinal plant used for ailments of the human gastrointestinal tract, were assessed for antibacterial efficacy in vitro, against eight enteropathogenic, extended spectrum β-lactamase enzyme producing multidrug resistant bacteria. Pathogenic bacteria were typified with serial biochemical steps. The double-disc diffusion–synergy test was used for the determination of extended spectrum β-lactamase producers. Sixteen antibiotics were used for determining antibiograms of eight isolated bacteria, using the disc-diffusion method. Antibacterial efficacies, of plant-extracts obtained using eight solvents, were monitored by the agar-well diffusion method. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of plant-extracts using solvents, methanol, ethanol, and acetone were determined by the micro-broth dilution method. Seven qualitative phytochemical tests were done with plant extracts. Of 16 antibiotics, resistant patterns were recorded with 14 antibiotics for Enterobacter aerogenes strains, 13 for Escherichia coli, 14 for Klebsiella sp., seven for Salmonella paratyphi, 15 for Salmonella typhi, 14 for two species of Shigella, and four for Vibrio cholerae. It was found that plant extracts using petroleum ether and n-hexane had the least antibacterial activity. Leaf and bark extracts using methanol, ethanol, and acetone registered the highest antibacterial activities with all these bacteria. The methanolic bark extract recorded MIC values, of 1.56 mg/mL against E. coli, Klebsiella sp., S. paratyphi, Shigella dysenteriae, and Shigella sonnei; 3.13 mg/mL against E. aerogenes and S. typhi; and 12.5 mg/mL against V. cholerae. The MBC values of the methanolic bark extract were: 12.5 mg/mL against E. coli, Klebsiella sp., S. dysenteriae, and S. sonnei; 25 mg/mL against E. aerogenes, S. typhi, and S. paratyphi; and 50 mg/mL against V. cholerae. Phytochemical analyses of methanolic leaf and bark extracts of T. alata confirmed the presence of alkaloids, terpenoids, reducing sugars, tannins, and flavonoids. The antibacterial efficacy of methanolic crude extracts revealed that leaves and bark of T. alata could serve as complementary/supplementary medicines to control multidrug resistant enteropathogenic bacteria.