To evaluate the anti-vibrio potentials of acetone and aqueous leaf extracts of Ocimum gratissimum
and determine its relevance in the treatment of vibrios infection.
The agar-well diffusion method was used for screening the extracts for their anti-vibrio
activity. Broth micro-dilution assay was used to determine the minimum inhibitory concentration (MIC)
and minimum bactericidal concentration (MBC) of the extracts. Time-kill assay was used to assess
bactericidal and/or bacteriostatic activity.
The acetone extract showed activity against 47.5 % (19/40) of the test bacteria, while the
aqueous extract had activity against 30 % (12/40). MIC and MBC values range for the acetone extract
were 0.625 – 5.0 mg/mL and 2.5 – 10 mg/mL respectively. The range of MIC exhibited by the antibiotic
(gentamicin) against the vibrios is 0.002 mg/mL and >0.256 mg/mL. Significant reduction in the bacterial
density was at 2 × MIC after a 4 h interaction period, while bacterial density after 6 and 8 h interactions
with extract was highly bactericidal. Growth inhibition and efficacy of the crude acetone extract were
observed to be both concentration- and time-dependent.
The bacteriostatic and bactericidal activities observed for Ocimum gratissimum leaf
suggest that the plant is a potential source of bioactive components that may be effective in the
treatment of vibrios infections.