Abstract

O. A. Aiyegoro, A. J. Afolayan and A. I. Okoh*

This study has been done to evaluate the interactions between acetone, chloroform, ethyl acetate and methanol extracts of Helichrysum longifolium in combination with six first-line antibiotics comprising of Penicillin G sodium, Amoxicillin, Chloramphenicol, Oxytetracycline, Erythromycin and Ciprofloxacin using both the time-kill and the chequerboard methods and against a panel of bacterial isolates comprised of referenced, clinical and environmental strains. The time-kill method revealed the highest bactericidal activity exemplified by a 6.7 Log 10 reduction in cell density against Salmonella spp. when the extract and Penicillin G are combined at ½ × MIC. Synergistic response constituted about 65%, while indifference and antagonism constituted about 28.33% and 6.67% in the time kill assay, respectively. The chequerboard method also revealed that the extracts improved bactericidal effects of the antibiotics. About 61.67% of all the interactions were synergistic, while indifference interactions constituted about 26.67% and antagonistic interactions was observed in approximately 11.66%. These suggest that the crude extracts of the leaves of H. longifolium could be potential source of broad spectrum antibiotics resistance modifying compounds.