Author(s): Syifa Nurisma Putri, Helmia Farida, Winarto and Tri Nur Kristina

Abstract: Escherichia coli and Pseudomonas aeruginosa are gram-negative bacteria that often cause infectious diseases in humans. Pharmacological therapy to overcome infection by these two species needs to be developed by utilizing natural ingredients, such as bitter melon fruit. This study aims to examine the antibacterial effects of bitter melon extract (BME) onE.coli and P. aeruginosa by in vitro method.In vitro experimental research with post test only control groupdesign was carried out using 5 groups, namely BME with gradual concentrations (100%, 50%, 25%, 12.5%, 0%) inoculated with bacteria and 1 positive control (K+) of gentamicin 16 mg/mL. Minimum Inhibitory Concentration (MIC) was assessed by comparing the clarity of the treatment solution with K+ and measuring the inhibitor zone diameter (IZD). Minimum bacterial concentration (MBC) was tested by culturing the treatment solution on solid media to see the resulted sterility. The inhibition of E.coli growth by BME 50% and 100% was not significantly different from K+ (p=1,000) and the IZD of BME50% for E.coli was 11 mm. The MBC of BME for E.coliwas not achieved by BME 12.5%-100%. The inhibitory growth of P. aeruginosa by BME 25% to 100% was not significantly different from K+ (p=1,000) and the IZD of BME 25% for P. aeruginosa was 13 mm. The MBC of P. aeruginosa was not achieved by BMEin all concentrations. BMEwas bacteriostatic againstP. aeruginosa with MIC 25% and probably bacteriostatic forE.coliwith MIC 50%. The higher BME concentration gives gretaer IZD results.