Biocontrol potential of phage Deep-Blue against psychrotolerant Bacillus weihenstephanensis

Hock, Louise [UCL] Leprince, Audrey [UCL] Tournay, Mathilde [UCL] Gillis, Annika [UCL] Mahillon, Jacques [UCL]

Some strains of the Bacillus cereus group can be implicated in two types of foodborne intoxication syndromes, namely diarrheal and emetic. The emetic syndrome results from the ingestion of the cereulide toxin produced by particular strains of B. cereus and 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. cereus group and shows a lytic activity against five of twelve B. weihenstephanensis. Its lytic cycle lasts 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 growth in food matrices such as milk rice. Finally, the application of Deep-Blue as preventive treatment was shown to efficiently control the development of B. weihenstephanensis biofilm.