Comparative analysis of bactericidal properties of synthetic peptides from the active center of GM-CSF - ZP2 against different gram-negative bacteria

Objective of this study was to carry out comparative analysis of bactericidal activity of synthetic peptide ZP2 (SP ZP2) against museum strains and clinical isolates of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii. Materials and methods. We used museum strains of E. coli (ATCC 25922) and P. aeruginosa ATCC 27853, as well as 104 clinical isolates of Enterobacteriaceae, including E. coli (n = 22) and K. pneumoniae (n = 82), and 98 clinical isolates of non-fermenting Gramnegative bacteria, including P. aeruginosa (n = 43) and A. baumannii (n = 55), isolated from patients with various gynecological and surgical infections. Bactericidal activity of SP ZP2 (final concentration 10 μg/ml) against the microorganisms was assessed by difference in optical density (OD) for experimental and control broth cultures after 20 min of contact of bacterial suspensions (5 x 10⁸ CFU/ml) with SP ZP2 (in control — with distilled water), adding meat-peptone broth and 4-hour incubation at 37 °C. The effect of SP ZP2 was expressed by the Bactericidal Activity Index (BAI, %). Results. Using the in vitro assays, we have found that SP ZP2 had a pronounced bactericidal effect on both the reference strains of E. coli and P. aeruginosa, and majority (95.5-98.2%) of the studied clinical isolates of Gram-negative bacteria, regardless of their species. With regard of the average BAI values, the tested bacterial species may be ranked by increasing their sensitivity to the synthetic ZP2 peptide as follows: P. aeruginosa (74.0±2.3%) — E. coli (77.6±3.5%) — K. pneumoniae (82.8±1.6%) — A. baumannii (84.3±1.7%). In addition, significant intraspecific variability of clinical isolates of Gram-negative bacteria was revealed for their sensitivity to bactericidal effect of SP ZP2. Conclusion. The synthetic ZP2 peptide is able to inhibit growth of Gram-negative bacteria, as well as exerts a bactericidal effect, thus considering it as a promising candidate for development of new effective drugs with combined immunobiological properties for combatting infectious and inflammatory conditions caused by the indicated microorganisms which show common resistance to a wide range of antimicrobial drugs used in clinical practice.