Abstract
Escherichia coli is one of the most important causes of foodborne diseases worldwide and it can be transmitted via the fecal-oral route. Antibiotics are considered the main treatment to control E. coli and due to the abuse and misuse of antibiotics, multidrug- resistant bacteria have emerged and become a challenge to public health worldwide. Bacteriophages are a group of viruses that can infect and kill bacteria and they are very specific toward their host bacteria.
Materials: Dairy samples from different locations in Cairo were collected to isolate E. coli strains and their specific bacteriophages. Isolated E. coli strains were subjected to an antibiotic sensitivity test using the disk diffusion method. In addition, isolates were identified by Polymerase Chain Reaction (PCR) and 16S rRNA. Bacteriophage was isolated, purified, amplified, and tested against the isolated E. coli strains. Consequently, the morphology of the isolated phage was studied using the Transmission Electron Microscope (TEM) and the phage genome size was determined by Pulsed-Field Gel Electrophoresis (PFGE). The stability of phage at different pH and temperature values, in addition to UV exposure was also studied. In addition, the replication dynamics of isolated phage was investigated in milk.
Results: Thirty-two dairy samples were collected and only twenty-seven isolates were E. coli positive. The 16S rRNA results of the selected isolate showed that the strain had a 98.26% sequence identity to the E. coli strains. The antibiotic sensitivity profile of the E. coli strain according to CLSI confirmed that it is a multi-drug resistant bacterium. One bacteriophage was isolated from Karish cheese and its morphology confirmed that it belongs to the Siphovirus family with an icosahedral capsid containing double strands of DNA and a non-enveloped phage with a long and non-contractile tail and a genome size of approximately 70 kb. The phage showed stability at different temperatures up to 70 °C and at different pH values between 4 and 12. In addition, the phage withstands UV exposure for one hour. The phage exhibited a lytic activity against E. coli growth in milk at a MOI of 2 after 3 hrs of incubation at 37 °C.
Conclusion: The results showed the high activity and ability of the isolated phage to control E. coli growth in milk. Thus, phage(s) can be used as a biocontrol agent to control pathogenic bacteria in milk and extend its shelf life.