Antibacterial activity of methylated egg white proteins against pathogenic G(+) and G(−) bacteria matching antibiotics

Native egg white protein with high level of acidic amino acid residues (pI = 4.8) and hydrophilic nature was transformed into its methylated derivative (MEW), acquiring rather hydrophobic and basic character (pI = 8). The MIC of MEW against ten studied bacteria (G(+) and G(−)) ranged between 0.5 and 1 μg/disc matching or excelling the comparative values of some known specific antibiotics (ranging from 1 to 7.5 μg/disc). Combinations of MEW (1 MIC) and different ready-made disc concentrations of antibiotics indicated either nil, antagonistic or synergistic antimicrobial effect. Replacing the antibiotic Ciprofloxacin by gradual levels of MEW (20–100 %) proportionally increased the potentiality to induce bigger sized inhibition zones. MEW (1 MIC) could inhibit the growth of 6 G(+) and 4 G(−) pathogenic bacteria in their liquid broth media during 24 h at 37 °C, indicating its broad and wide specificity. TEM examination indicated the susceptibility of the two types of bacteria (G(+) and G(−)) to the antimicrobial action of MEW as manifested in different signs of cellular deformations, confirming its broad specificity and its mode of action was rather targeting the cell wall and cell membrane.