Evaluation of Antimicrobial Properties of Tylosema fassoglense Root and Leaf Extracts against Salmonella typhi

Introduction: Typhoid fever remains a major public health concern in many low- and middle-income countries due to the increasing emergence of antimicrobial-resistant Salmonella enterica serovar Typhi. The declining effectiveness of conventional antibiotics has renewed interest in medicinal plants as potential sources of novel antibacterial agents. Tylosema fassoglense, a medicinal plant traditionally used in western Kenya for the treatment of gastrointestinal disorders, has received limited scientific evaluation for its antityphoid activity.
Methods: An experimental comparative in vitro study was conducted to determine the minimum inhibitory concentration (MIC) of methanolic root and leaf extracts of Tylosema fassoglense against Salmonella enterica serovar Typhi. Plant materials were collected from the Mt. Elgon region of Trans-Nzoia County, Kenya, shade-dried, pulverized, and extracted using methanol. A reference strain of S. Typhi was obtained from the Masinde Muliro University of Science and Technology Microbiology Laboratory. Antibacterial activity was evaluated using the broth microdilution method in accordance with Clinical and Laboratory Standards Institute (CLSI) guidelines. Two-fold serial dilutions of the extracts (31.25–1000 µg/mL) were tested in triplicate. Chloramphenicol was used as the positive control, while Mueller–Hinton broth with bacterial inoculum and 5% DMSO served as the growth and solvent controls, respectively.
Results: Both methanolic root and leaf extracts inhibited the growth of Salmonella enterica serovar Typhi in a concentration-dependent manner. The root extract demonstrated greater antibacterial activity, with MIC values ranging from 125–250 µg/mL (mean MIC = 208.3 µg/mL), whereas the leaf extract exhibited MIC values ranging from 250–500 µg/mL (mean MIC = 416.7 µg/mL). Chloramphenicol exhibited the greatest antibacterial activity (MIC ≤31.25 µg/mL). One-way ANOVA demonstrated a highly significant difference in antibacterial activity among the three treatments (F(2,6)=175.0, p<0.001). Independent-samples t-tests further showed that the root extract exhibited significantly greater antibacterial activity than the leaf extract, while chloramphenicol was significantly more effective than both plant extracts (p<0.05).
Conclusion: Methanolic extracts of Tylosema fassoglense possess in vitro antibacterial activity against Salmonella enterica serovar Typhi, with root extracts exhibiting substantially greater potency than leaf extracts. These findings support the traditional medicinal use of T. fassoglense and highlight the roots as a promising source of antibacterial phytochemicals for future isolation, characterization, and development of plant-derived antityphoid agents.

Tylosema fassoglense, Salmonella Typhi, Typhoid fever, antimicrobial activity, Antibacterial activity

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