Isolation and characterization of Proteus mirabilis bacteriophage T2 and its application

Public health problems caused by foodborne illnesses have become increasingly serious. Although it was usually regarded as an opportunistic pathogen causing urinary tract infections in humans, recent years have seen an increasing number of foodborne infections related to P. mirabilis. Therefore, it was crucial to develop effective strategies to control this bacterium. In this study, the bacteriophage T2 isolated from cattle dung formed numerous clear plaques with a diameter of approximately 3 mm on the bacterial lawn of P. mirabilis Y22 using a double-layer agar method. Electron microscopic and genomic DNA analyses suggested that phage T2 was a recently discovered virulent phage, classified under the genus Novosibovirus within the subfamily Slopekvirinae. Analyses of phylogeny and genomics indicated that there was a relatively close evolutionary relationship with Proteus phage. Notably, phage T2 exhibited excellent environmental adaptability and showed stable lytic activity across a wide range of pH values (4-10) and temperatures (20-50 °C), even in a 3 M NaCl solution. Phage T2 has the ability to inhibit and kill P. mirabilis Y22 in a dose-dependent manner in LB broth, and phage T2 was capable of significantly inhibiting biofilm formation and breaking down established biofilms. The growth of P. mirabilis Y22 in milk and sausage was successfully suppressed at an MOI of 100 (P < 0.01). Moreover, phage T2 can lyse and kill bacteria in G. mellonella, thereby increasing their survival rate. These results indicated that the lytic phage T2 could be a promising candidate for managing P. mirabilis contamination in food products.