Gut commensals and pathogens, such as Bacteroides fragilis and Pseudomonas
aeruginosa, were cultured in brain heart infusion broth (Oxoid, Basingstoke,
United Kingdom) at 37°C, and Bacillus cereus, Brevibacterium casei, and Listeria
monocytogenes were cultured at 30°C. Overnight cultures were stored at 20°C
until further processing.