Antibacterial evaluation of metronidazole and its derivative in the treatment of Escherichia coli and Staphylococus aureus

Abstract

Studies and applications of metronidazole and its derivatives have received massive attention for over six decades, however the fact that certain microorganisms are resistant to metronidazole raises a lot of curiosity hence the need to synthesize and test the antibacterial effectiveness of metronidazole and some of its derivatives on Escherichia coli and Staphylococcus aureus. Antibacterial evaluation was carried out on two microbial organisms (Escherichia coli and Staphylococcus aureus) using Agar disk
diffusion method with Metronidazole (Sample 1) and two of its derivatives namely 1-(2 Hydroxyethyl)-2-methyl-5-aminoimidazole (sample 2) and Metronidazole-Naphthol (sample 5) as antibiotics. A stock solution of 1000 mg/mL of Sample 1 was used as control to prepare other concentrations of 0.1, 1.0, 10.0, 100.0, 250.0 and 500.0 mg/mL of Samples 1, 2 and 5 respectively. The purity of samples 1, 2 and 5 were verified from their melting points of 158 – 160 ⁰C, 154 – 156 ⁰C and 145 – 146 ⁰C respectively. Results obtained showed that the diameter of the zone of Escherichia coli inhibited by Sample 1 were 2.5, 4.5, 6.0 and 19.0 mm at sample concentrations of 100, 250, 500 and 1000 mg/ml respectively while Staphylococcus aureus was inhibited by the same sample at a diameter of 3.5, 6.0 and 15.0 mm at sample concentrations of 250, 500 and 1000 mg/L respectively. Sample 2 has no antibiotic effect on both micro-organisms while Sample 5 displayed antibiotic effects on Escherichia coli and Staphylococcus aureus only at high sample concentration of 1000 mg/mL by inhibiting a 19.0 mm diameter of both micro-organisms respectively. The United States Food and Drug Administration (FDA) recommends that an effective antibiotic must cover an inhibition zone of not less than 21.0 mm diameter of a micro-organism, this therefore shows that both micro-organisms are resistant to metronidazole and its derivatives (1-(2-Hydroxyethyl)-2-methyl-5-aminoimidazole and Metronidazole naphthol). Staphylococcus aureus however displayed more resistance on the antibiotic samples than Escherichia coli.