ISSN 2326-7267
International Journal of Pharmacy and Pharmacology ISSN: 2326-7267 Vol. 3 (2), pp. 001-008, February, 2012. © International Scholars Journals
Full Length Research Paper
In vitro antibacterial activities of crude extracts of the leaves of Helichrysum longifolium in combination with selected antibiotics
O. A. Aiyegoro1, A. J. Afolayan2 and A. I. Okoh1*
1Applied and Environmental Microbiology Research Group (AEMREG), Department of Biochemistry and Microbiology, University of Fort Hare, Alice 5700, Private Bag X1314, South Africa.
2Phytomedicine Group, Department of Botany, University of Fort Hare, Alice 5700, Private Bag X1314, South Africa.
Accepted 26 September, 2011
Abstract
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.
Key words: Synergism, antibiotics, extracts, chequerboard, time-kill.