Antibacterial Activity of Melia azedarach Leaves against Salmonella typhi and Streptococcus pneumoniae

Abstract

Antimicrobial drug resistance is increasingly becoming an important global problem.  Among the major causes for concern is drug resistant Streptococcus pneumoniae and Salmonella typhi, which have become resistant to at least one antibiotic.  This challenge has lead scientists to investigate plants as potential sources of antimicrobial agents since they have been used to treat diseases long before the discovery of antibiotics.  In Zimbabwe, typhoid is a leading cause of mortality and morbidity due to poor sanitation and poor treatment regimes.  Traditionalists are using Melia azedarach leaves for the treatment of diarrhea, a typhoid symptom.  Thus, this study focused on validating the use of M. azedarach leaves for medicinal purposes by determining their antibacterial activity against S. pneumoniae and S.typhi, the causative agent of typhoid fever.  Melia azedarach leaf constituents were extracted using ethanol, ethylacetate, hexane, dichloromethane and methanol.  Their antibacterial activities were assessed using the agar disk diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays.  Haemolysis assay was carried out to determine the toxicity of the potent extracts.  The ethanol and hexane extracts showed antibacterial activity against S. typhi whilst dichloromethane and hexane extracts showed antibacterial activity against S. pneumoniae.  Minimum inhibitory concentrations for ethanol and hexane against S. typhi were < 1 µg/ml and 15.6 µg/ml respectively, whilst their minimum bactericidal concentrations were 31.25 µg/ml and 250 µg/ml.  The MICs for dichloromethane and hexane extracts against S. pneumoniae were 31.25 µg/ml and 62.5 µg/ml respectively, whilst their MBCs were 31.25 µg/ml and 125 µg/ml.  The extracts ethanol, hexane and dichloromethane had haemolytic activity of 63 %, 62 % and 59 % respectively.  Therefore, these results validate the use of M. azedarach leaves for medicinal purposes.  However, these leaves may be toxic to human consumption, thus there is need for further investigation on their toxicity in vivo.