Effects of stool-derived lipopolysaccharide (LPS) combined with toxin B on interleukin 1β (IL-1β) and tumor necrosis factor alpha (TNF-α) production. Crude stool LPS extracts from different individuals were incubated with or without toxin B (50 ng/mL) and the effects on IL-β (A) and TNF-α (C) were measured. Cytokine levels produced by incubation of stool-derived LPS alone or together with toxin are represented by black and gray bars, respectively. Numbers above columns represent the fold increase in cytokine level produced by stool-derived endotoxin combined with toxin B relative to stool-derived endotoxin alone. B, The addition of colistin B (1 mg/mL) prevented the IL-1β produced by the co-incubation of toxin B with 2 representative stool samples. D, Supernatant IL-1β levels following incubation of PBMCs with LPS, which was obtained by phenol extraction, are shown. For A, C, and D, statistical comparisons are between stool-derived endotoxin with or without toxin B. For B, comparisons are between stool and toxin B with or without colistin. Dotted lines represent the 25th percentile and 75th cytokine percentiles for co-incubation of stool and toxin. *P value < .05.