Isolation and molecular characterization of bacteriophages isolated from lake water and their application in foods against Bacillus cereus.

Abstract

Objectives: Bacteriophages are viruses that specifically target and kill bacteria. Bacteriophages are considered safe for humans, making them suitable for use in food applications Therefore, this study was conducted to isolate, characterize, and apply bacteriophages from the environment to control food spoilage bacteria.

Results: Bacteriophages were isolated by using Bacillus cereus (B. cereus) as reference host. We found bacteriophage BC-VP titers (1.16 ± 0.18 × 10⁹ PFU/mL) and BC-AJ (1.72 ± 0.19 × 10⁸ PFU/mL). Both bacteriophages were polyvalent, targeting not only B. cereus, but also lysing enteropathogenic Escherichia coli (EPEC) and enterotoxigenic Escherichia coli (ETEC) with different efficiencies. Bacteriophage BC-VP and BC-AJ miMOI were determined to be 0.01 and 1, respectively. Bacteriophage BC-VP morphology was analyzed using Transmission Electron Microscope (TEM) and categorized as Myoviridae family from the order of Caudovirales. Both bacteriophages showed significant bacterial reduction when applied to artificially contaminated cooked rice and pasteurized milk. The reduction number was higher in pasteurized milk at 28℃ for BC-VP (93%) and BC-AJ (90%). Molecular characterizations were performed and showed that BC-VP was 96.88% a virulent bacteriophage. Also, no sign of antibiotic resistance gene in BC-VP and genes related to lytic cycle such as putative tail lysin and tail fiber, were annotated.