Inhibition of antibiotics-resistant bacteria by naturally modified proteins

Abstract

Most antibiotics cannot face multidrug-resistant bacteria (MDR), necessitating the search for new antibacterials based on natural resources. Native or modified natural legume proteins exhibited a wide range of potent antimicrobial properties. Sixteen bacterial isolates were mapped for antibiotic resistance according to CLSI, showing resistance in the range of (42-92%) and (58-92%) in the case of the Gram-positive and Gram-negative bacteria, consecutively. White native Phaseolus vulgaris protein (NPP) was isolated from the seeds and methylated (MPP). The MIC range of MPP against 7 MDR bacteria was 10-25 times lower than NPP and could (1 MIC) considerably inhibit their 24hr liquid growth. MPP showed higher antibacterial effectiveness than Gentamycin, the most efficient antibiotic versus Gram-positive bacteria and the second most efficient against Gram-negative bacteria. However, MPP recorded MICs against the seven studied MDR bacteria in the 1-20 µg/mL range, which is the same for Gentamycin. The combination between Gentamycin and MPP produced synergistic effects against the seven studied bacteria, as confirmed by the Transmission Electron Microscopic images. The antimicrobial activity of MPP against the seven MDR bacteria remained stable after two years of cold storage at 8-10 C as contrasted to Gentamycin which lost 20-72% of its antimicrobial effectiveness.