In-vitro Assessment of Antibacterial Activity of Local ‘Typhoid-Cure’ Cocktail of Leaves of Five Medicinal Plants Against Multidrug-Resistant Salmonella typhi from Clinical Sources

For centuries, medicinal plants have been used for curative purposes in traditional healthcare systems worldwide. In Nigeria, many indigenes opt for local herbs made from medicinal plants. However, the efficacy of local herbs needs to be consistently validated. This study evaluated the effectiveness of the extracts of five types of plant leaves (Azadirachta indica, Carica papaya, Gossypium hirsutum, Jatropha curcas and Ricinus communis) against clinical isolates of Salmonella typhi. The antibiotic susceptibility of the isolates was evaluated using the disk-diffusion method. Additionally, the crude aqueous extracts, along with a combined mixture of all five plant extracts, were assessed for in vitro antimicrobial activity through the agar well diffusion assay. Phytochemical analysis of the plant samples was conducted to identify and evaluate the presence of secondary metabolites. Phytochemical analyses revealed the presence of steroids, flavonoids, glycosides, and tannins in all plants, but no terpenoids. Altogether, 57 S. typhi isolates were isolated from 280 rectal swabs collected from hospital patients (20.4%). All were multidrug-resistant, with 100% resistance to sulfonamide, followed by ticarcillin and fosfomycin at 93.0% each, while resistance to nitrofurantoin was lowest at 26.3%. Neither crude extracts nor the reference sample displayed any antibacterial activity. However, a particular preparation of A. indica (10g extract in 50mL hot water) revealed zones of inhibition (≥7mm and ≤12mm) against 10.5% of isolates (6/57). None of the plant aqueous extracts exhibited noteworthy antibacterial activity against any of the 57 S. typhi strains. Therefore, there is an urgent need to curtail the regular dispensing of these local herbs until further studies are done to validate their efficacy and establish appropriate administration regimes for optimum effect.