Bacteriostatic and Bactericidal effects of ethyl acetate root bark extract of Terminalia avicennioides on Methicillin-resistant Staphylococcus aureus

Abstract

Root bark extract of Terminalia avicennioides was obtained by cool maceration with 750 ml n-hexane, chloroform, ethyl acetate and methanol, independently for 48 h using soxhlet extractor. ATCC 33591 standard strains of methicillin-resistant Staphylococcus aureus (MRSA) was used. Strain resistance to methicillin/oxacillin antibiotic was verified by a retest of its sensitivity to oxacillin antibiotic. The antimicrobial test and zone of inhibition were determined using the agar well diffusion method. The isolated bioactive fractions of the extract were subjected to FTIR and GC-MS analysis. Results revealed both fractions; (TLb4 and TLb17) were both bacteriostatic and bactericidal. The growth of MRSA was inhibited at extract concentrations of 60, 120, 180 and 240 µg/ml, within the susceptible range of ≥ 14 mm, with a mean inhibitory zone sensitivity of 14 mm at 60 µg/ml, 15.76 mm at 120 µg/ml and 15.33 mm at 180 µg/ml for fraction TLb4 and 15.33 mm at 60 µg/ml, 17.33 mm at 120 µg/ml and 20 mm at 180 µg/ml for TLb17 (≥ 14 mm). GC-MS detected oleic acid and analogs of palmitic acid as pharmacological active compounds of both fractions. FTIR showed the presence of alkyl halides. These bioactive agents revealed could be effective therapeutic agents for the treatment of MRSA. Key words: Methicillin-resistant, Staphylococcus aureus, inhibition, bacteriostatic, bactericidal, Terminalia avicennioides.