Biocontrol potential of phage Deep-Blue against psychrotolerant Bacillus weihenstephanensis

Abstract Some strains of the Bacillus cereusgroup can be implicated in two types of foodborne intoxication syndromes, namely diarrheal and emetic. The emetic syndrome results from the ingestion of the cereulidetoxin produced by particular strains of B. cereusand Bacillus weihenstephanensis. It represents a major concern since it can lead, in severe cases, to the death of the intoxicated patients. This study aimed to characterize the virulent phage Deep-Blue and investigate its biocontrol potential against psychrotolerant B. weihenstephanensis . This myovirus was isolated from an agricultural soil and is stable for at least 6 months at 4 °C. It is specific to members of the B. cereusgroup and shows a lytic activity against five of twelve B. weihenstephanensis . Its lytic cyclelasts less than 1 h with a final phage progeny of ca. 300 virions. Regarding its bactericidal potential, Deep-Blue was able to reduce B. weihenstephanensis contamination under laboratory conditions (LB broth) and in milk, and to control bacterial growthin food matrices such as milk rice. Finally, the application of Deep-Blue as preventive treatmentwas shown to efficiently control the development of B. weihenstephanensis biofilm.