Antibacterial activities of aqueous and ethanolic leaf extracts of Abrus precatorius against urinary tract pathogens and Listeria monocytogenes isolated from vegetables

Abstract

Medicinal plants have been used traditionally to treat infectious diseases since the origin of mankind. The increase in multidrug resistant organisms associated with conventional agents has ignited a lot of interest in traditional medicine. The aim of this study was to determine the antibacterial activities of ethanolic and aqueous extracts of Abrus precatorius leaf against ten clinical microbial isolates mostly (except Listeria monocytogenes isolated from leafy vegetable) recovered from urinary tract infected patients. The broth micro-dilution technique was used for the assay. The ethanolic extract was inhibitory to K. pneumonia, P. aeruginosa, E. faecalis, S. aureus, L. monocytogenes and P. mirabillis with minimum inhibitory concentration (MIC) (mg/ml) values of 23.4 ±7.8 to 46.9 ± 15.6, 31.3 ± 0.0 to 46.9 ± 15.6, 23.4 ± 7.8 to 156.3 ± 93.8, 23.4 ± 7.8 to 250.0 ± 0.0, 140.6 ± 109.4 and 46.9 ± 15.6 respectively. The aqueous extract was also inhibitory to K. pneumonia, P. aeruginosa, E. faecalis, S. aureus, L. monocytogenes and P. mirabillis at MICs (mg/ml) of 15.6 ± 9.4, 15.6 ± 9.4, 7.8 ± 4.7 to 9.4 ± 3.1, 4.7 ± 1.6 - 4.7 ± 1.6, 37.5 ± 12.5 and 9.4 ± 3.1 respectively. While ethanolic extract was bactericidal to S. aureus STAPH2, L. monocytogenes and P. mirabillis, the aqueous extract was only bactericidal to P. aeruginosa PSDOI and S .aureus STAPHI. Ofloxacin and gentamycin used as positive controls were effective against all isolates tested at microgram concentrations. The present in vitro study scientifically authenticates the traditional use of extracts of Abrus precatorius leaf for treatment of some bacterial infections in our region.