Antibacterial activity of <i>Citrullus lanatus</i> seed extract against clinical isolates of <i>Klebsiella pneumoniae</i> and <i>Staphylococcus aureus</i>

Abstract

As a result of increased emergence of bacterial resistance to the conventionally used antibiotics, it is necessary to search for alternatives from other sources like plant materials. This study was aimed at evaluating the in vitro antibacterial activity of Citrullus lanatus seed extract against isolates of Klebsiella pneumoniae from urine and Staphylococcus aureus from wound. The seeds were extracted using distilled water and methanol via cold maceration and then analysed for the presence of phytochemicals using standard methods. Tannins, steroids, cardiac glycosides and carbohydrates were present in both extracts. Only the aqueous extract contained alkaloids. The antibacterial activity of the two extracts was determined by agar well diffusion method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using broth dilution method. The aqueous extract had better activity than the methanol extract, having inhibition zones of 20 mm and 23 mm at 200 mg/mL and, 10 mm and 11 mm at 25 mg/mL against Klebsiella pneumoniae isolates respectively, and mean zone of inhibition between 27.50 mm to 29.33 mm at 200 mg/mL and, 16.50 mm to 17.33 mm at 25 mg/mL against Staphylococcus aureus isolates with MIC and MBC values of 0.195 mg/mL and 0.39 mg/mL against Klebsiella pneumoniae and, mean MIC and MBC values ranging from 0.30 mg/mL to 0.39 mg/mL and 0.78 mg/mL to 2.73 mg/mL against Staphylococcus aureus isolates. The results obtained reveal the potential use of Citrullus lanatus seeds in the development of standard antibiotics.