Isolation of lytic bacteriophages against antibiotic-resistant escherichia coli and determination of the lytic spectrums

Escherichia coli is a pathogenic bacterium that causes colibacillosis in poultry. Antibiotics are used extensively in the treatment of colibacillosis. On the other hand, as a result of excessive and incorrect use of antibiotics, E. coli strains have become resistant to antibiotics recently. This complicates the fight against colibacillosis and emerges as an important problem. Bacteriophages are defined as viruses that infect bacteria and can be considered as an alternative to antibiotics. This study was carried out to isolate lytic bacteriophages against E. coli strains obtained from colibacillosis-suspected broilers and to determine the lytic activities of isolated bacteriophages against various clinical E. coli strains. In the study, the cecums of 14 colibacillosis suspected broilers were used for the isolation of E. coli. Detection of bacteriophages was carried out by the soft agar method from the mixture formed by combining 14 caecum samples. As a result of the study, 14 E. coli were isolated and antibiotic resistance profiles of 6 selected strains were determined. E. coli strains were found to be resistant to at least 3 antibiotics. E. coli strains were found to be resistant to lincomycin (100%), bacitracin (100%), amoxicillin (83%), ciprofloxacin (83%), sulfamethoxazole (67%), colistin (17%) and ampicillin (17%). In contrast, E. coli strains are sensitive to tetracycline and gentamicin antibiotics. Four bacteriophages were detected by spot test method against 6 multi-antibiotic resistant E. coli strains and 3 of them (BF1, BF2, BF4) were purified. The titers of isolated bacteriophages were found between 1.41 x 106 and 2.04 x 106 PFU/ml before amplification, and between 4.02 x 108 and 4.36 x 1011 PFU/ml after amplification. The lytic spectra of bacteriophages were determined against 9 clinical E. coli strains in addition to the host bacteria used in the study. While the lytic spectrum of the BF1 phage and the phage cocktail prepared by mixing all three phages were found to be 22.2%, the BF2 and BF4 phages did not show lytic activity against the clinical strains.