Antimicrobial activity of <i>Sida acuta, Phyllanthus amarus and Phyllanthus muellerianus</i> against microorganisms implicated in urinary tract infections

Abstract

Increasing level of antimicrobial resistance among bacterial pathogens causing Urinary Tract Infection (UTI) is one of the most significant public health challenges globally. Hence, the search for alternatives from medicinal plants. This study investigated the efficacy of Phyllanthus amarus (PA), Phyllanthus muellerianus (PM) and Sida acuta (SA) leaf extracts on microorganisms implicated in UTI. Mid-stream urine samples collected from 100 patients clinically diagnosed with UTI were cultured. The microorganisms isolated were identified using their morphological and biochemical characteristics. Methanol leaf extracts of the three plants were obtained by cold maceration in 60% methanol. Crude extract of PM was thereafter purified by solvent partitioning. Antibiotic susceptibility test was determined using the Kirby Bauer disc diffusion. Antimicrobial effects of the extracts and oil was ascertained using agar well diffusion. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentrations (MBC) were also determined. Rate of kill and mechanism of action of the purified extract of PM on isolates were investigated. Cytotoxicity of plant extracts were assayed on brine shrimps while synergism of the purified extract with ciprofloxacin was ascertained using overlay inoculum susceptibility disc method. Antioxidant and phytochemical analyses of the extracts were conducted using standard methods. Phytochemical analysis of the leaf extracts showed the presence of alkaloids, tannins, saponins and steroids. Antioxidant assay also indicated SA had the highest total flavonoids and phenol content of 339.86 mgQUE/g and 27.63 mgGAE/g. Microorganisms isolated include: Escherichia coli (24%), Proteus mirabilis (24%), Staphylococcus aureus (19%), Klebsiella pneumoniae (13%), Candida albicans (11%), Enterobacter sp. (5%) and Citrobacter sp. (4%). The crude extract of PA had zone of inhibition ranging from 16.7 ± 1.53 mm to 24 ± 1.00 mm while SA crude extract had 14.7 ± 1.53 mm to 27 ± 2.00 mm. PM crude extract had inhibition zones of 17 ± 1.00 mm to 22.3 ± 2.12 mm. The MIC and MBC ranged from 6.25 mg/ml to 50 mg/ml and 12.5 mg/ml to 50 mg/ml respectively. Ethyl acetate fraction of PM showed the highest percentage yield and had a zone diameter range from 13.5 ± 1.00 mm to 28 ± 1.53 mm with MIC and MBC ranges of 6.25 mg/ml – 12.5 mg/ml and 25 mg/ml to 50 mg/ml respectively. Synergism with ciprofloxacin was observed at 25% of the microorganisms, 50% antagonism and 25% additively. Toxicity analysis showed lethal dose concentrations of 19.05 mg/ml, 25.12 mg/ml and 130.11 mg/ml for PM, PA and SA respectively. The findings of this study suggest that the methanol extracts of the medicinal plants used in this study does possess a potent lead molecule in combating microorganisms causing UTI.

Key words: Antimicrobial activity, Phyllanthus muellerianus, Phytochemicals, Toxicity, UTI,