ANTIBACTERIAL ACTIVITY OF VERNONIA AMYGDALINA EXTRACTS AGAINST MULTI-DRUG RESISTANT GRAM-POSITIVE AND GRAM-NEGATIVE BACTERIA

Abstract

Abstract: The incidence of antibiotic resistance is one of the challenges in the treatment of different ailments. Hence, this study focused on the use of V. amygdalina (ethanolic and methanolic) extracts on some selected bacterial isolates. Different concentrations of the extracts were prepared and the residues were re-suspended in the solvents. The zone of inhibition, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and antibiotic susceptibility patterns were determined according to standard methods. The ethanolic extract appeared to produce better antibacterial effect than methanolic extract. K. pneumoniae and S. marcescens were inhibited by ethanolic extract of 12.5-200mg/ml used. However, only S. aureus was inhibited by all methanolic extract concentrations used. Most of the isolates (83.3%) had lower MIC in ethanolic extract when compared with methanolic extract. The MIC of the isolates in the ethanolic and methanolic extracts ranged from 12.5-100mg/ml and 25-100mg/ml respectively. Two of the isolates, B. cereus and K. pneumoniae did not cease to grow on MBC plates even at the highest concentration of 200mg/ml used. All the isolates showed multiple antibiotic resistance patterns with AMR index range of 0.63-1.0. All the isolates were resistant to augmentin, cefexime, cefuroxime, ceftazidime and nitrofurantoin. The order of susceptibility of the isolates to the antibiotics were gentamicin (83.3%) > ofloxacin (66.7%) > ciprofloxacin (33.3%). It is concluded in this study that the extracts of V. amygdalina inhibited 83% of the isolates at lower concentration of 25mg/ml, were bactericidal at 100-200mg/ml for 66.7% of the isolates and produced higher inhibition zone in comparison with the standard antibiotics on the isolates.