In vitro evaluation of the interactions between acetone extracts of Garcinia kola seeds and some antibiotics

The effect of combinations of the acetone extract of Garcinia kola seeds and six first-line antibiotics was investigated by means of fractional inhibitory concentration (FIC) indices as well as by the use of time kill assays. Using the FIC indices, synergistic interactions were observed largely against gram positive organisms (FIC indices of 0.52 - 0.875) with combinations against gram negatives yielding largely antagonistic interactions (FIC indices of 2.0 to 5.0). The time kill assay detected synergy against both gram negative and gram positive organisms with a ≥ 1000 times (≥ 3Log10) potentiation of the bactericidal activity of tetracycline and chloramphenicol (against E. coli ATCC8739 and K. pneumoniae ATCC10031) as well as amoxycillin and penicillin G against Staphylococcus aureus ATCC 6538. Combinations involving erythromycin and ciprofloxacin consistently gave antagonistic or indifferent interactions. We conclude that the acetone extract of G. kola can be a potential source of broad spectrum antibiotics resistance modifying compounds.