Antibacterial Activity of Lactoferrin Chimera and its Synergistic Effect with Gentamicin, Cefazolin, and Ceftazidime against Pathogenic Ggram- Negative Bacteria

 It is essential to introduce new antimicrobials or to evaluate the synergistic effect of existing compounds as a therapeutic strategy against microbial strains resistant to one or more antibiotics. The aim of this study was to evaluate the antimicrobial activity and synergistic effect of lactoferrin chimera (cLF) in interaction with some common therapeutic antibiotics.

 The antimicrobial activity of cLF and the antibiotics including gentamicin, cefazolin, and ceftazidime were determined by the minimum inhibitory concentration (MIC) method and subsequently, the synergistic effect of this peptide with each of the mentioned antibiotics was checked against E coli, P. aeruginosa and S. typhi were investigated and the minimum fraction inhibitory concentration (FIC) was reported. Release of cytoplasmic materials, plotting of survival curves, and activity of peptides alone and in combination with antibiotics were evaluated, and bacterial cell morphology investigating was performed using scanning electron microscopy at MIC and FIC concentrations.

 The synergistic effect was observed in the combination of cLF with all antibiotics. The results showed that at FIC concentrations, material release from the cytoplasm and the number of surviving cells were significantly higher and lower than when peptides or antibiotics were used alone, respectively. The activity of peptides and antibiotics at FIC concentration was increasing and SEM images at this concentration showed severe membrane damage of bacterial cells.

 The use of cLF and antibiotics at FIC concentrations reduces the dose of both substances.