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Sweet basil (Ocimum gratissimum) is widely consumed as green leafy vegetable and used in folkoric medicine in
the treatment and management of both infectious and non-infectious diseases. This study was designed to
investigate the effect of ethanolic leaf extract of O. gratissimum on the immune system of Wistar rats infected
with Salmonella typhi. Forty Wistar rats were divided into eight groups of five rats each. Groups 1, 2A, and 2B
were infected with Salmonella typhi and observed for signs of infection before being treated with 200mg/kg and
400mg/kg extract of O. gratissimum; Groups 3A and 3B were fed with 200mg/kg and 400mg/kg extract of O.
gratissimum respectively in addition to their normal diet; Group 4 was infected with S. typhi and left untreated;
Group 5 was infected with S. typhi, observed for signs of infection and later treated with 250mg/kg of
ciprofloxacin; while Group 6 was fed basal diet and water only. Blood and urine were collected from the rats at
the end of the experiment. Protein was present in all the urine examined before, during, and after infection, while
glucose, blood, and ketone were absent. The urine collected before and during infection contained crystals
(majorly triple phosphate) and bacteria when examined microscopically. Apparently, O. gratissimum did not
affect metabolic activities of the experimental Wistar rats. White blood cells and RBCs in the groups pre-treated
with the extract did not differ significantly; hence the use of ethanolic leaf extract of O. gratissimum as
prophylactics is not encouraged. Compared to ciprofloxacin, the ethanolic extract at 200mg/kg significantly
(p<0.05) increased the production of RBCs. However, production of neutrophils and lymphocytes which are
essential immune cells did not differ significantly (p<0.05) between groups. Resultantly, this study revealed that
ethanolic leaf extract of O. gratissimum may enhance erythropoiesis but not immunostimulation during S. typhi
infection.
Keywords: Ocimum gratissimum, Salmonella typhi, immune system, Wistar rats, ethanolic extract