Effectiveness of Plectranthus cyaneus leaf extracts against streptococcus pyogenes

Abstract

This study was carried out mainly to provide preliminary scientific data on the antibacterial activities of Plectranthus cyaneus leaf extracts against Streptococcus pyogenes so as to aid in the ultimate goal of designing cheap effective alternative antimicrobial compounds to currently antibiotic resistant infections caused by Streptococcus pyogenes. The specific objectives of this study were to determine the diameter of the zones of inhibition and the minimum inhibitory concentration of Plectranthus cyaneus leaf extracts against Streptococcus pyogenes. Extraction of the bioactive ingredients from Plectranthus cyaneus leaves was done in two different extraction media ie, ethanol and hot water. The antibacterial activity of Plectranthus cyaneus leaf extracts against Streptococcus pyogenes was determined by measuring the diameter of the zones of inhibition and by determining the minimum inhibitory concentration (MIC). Besides the two treatments, Penicillin and sterile distilled water were used as the positive and negative controls respectively. To determine the diameter of the zones of inhibition of Plectranthus cyaneus leaf extracts against Streptococcus pyogenes, the Agar well diffusion method was used while the minimum inhibitory concentration (MIC) of the leaf extracts was determined using the Resazurin-based 96-well plate microdilution method. From the treatments, the positive control(Penicillin) produced the largest zone of inhibition (33mm), followed by the ethanolic extract(16mm), followed by the hot water extract(13mm) while the negative control(sterile distilled water) did not produce any zone of inhibition. The hot water extract had the highest MIC value (1000mg/ml), followed by the ethanolic extract (125mg/ml), followed by the positive control which had the lowest MIC value (7.8125mg/ml). Based on the mean diameter of the zones of inhibition and the minimum inhibitory concentration of the ethanolic extract(16mm and 125mg/ml respectively), Plectranthus cyaneus leaves hold a promise as a potential ethnopharmacological source for treating infections caused by Streptococcus pyogenes