Effect of Purified Bacteriocin from Acinetobacter baumannii on some Pathogenic and Environmental Isolates and Its Inhibitory Effect on Hemolysin Production from S. aureu

Abstract

From 122 isolates 63 isolates were diagnosed as Acinetobacter baumannii. The highest percentage of isolation was 37 (58.7%) from wounds and the lower percentage was 7 (11.1%) from burns. The antimicrobial susceptibility test was performed the highest resistance percentage was Cephalothin at 95.2 %, while the low percent was gentamycin was 47.6 %. The minimal inhibitory concentrations (MICs) for imipenem were tested the MIC values for imipenem resistant isolates ranged from 16 µg ml^-1 to 64 µg ml^-1. Bacteriocins proteinaceous or peptidic toxins produced by bacteria offer promising potential as substitutes or conjugates to current therapeutic compounds. Three methods were used to detect bacteriocin production Acinetobacter baumannii, Agar well diffusion method, cup assay, and Disk method. From 63 Acinetobacter baumannii isolates 27 (42.85%) isolates were able to produce bacteriocin.  Agar well diffusion method was the best for detection and the best isolate was (No. 48) for bacteriocin production for all methods. Bacteriocin purified by two steps method ammonium sulfate precipitation followed by gel filtration chromatography on Sephadex G150 column and characterized. The specific activity was 1541U mg protein with 6.3 bacteriocin folds and 64% recovery yield. The molecular weight of bacteriocin was (14000) Da. Bacteriocin activity was stable at pH values (3-9). Also, bacteriocin showed high thermostability at different temperatures (20-80)°C for (30) min. The antimicrobial activity of crude and purified Acinetobacter baumannii bacteriocin from (No. 48) isolate was maximum antibacterial activity against E. coli , S. aureus (purified 30 mm, crude 22 mm for both) and K. pneumonia isolates (purified 25 mm, crude 20 mm).