Loss of spore OD600 of C. difficile isolates during incubation in A) BHIS supplemented with taurocholate and chenodeoxycholate; B) BHIS supplemented with taurocholate; or C) BHIS alone.

C. difficile spores were heat treated at 60°C for 25 min and then incubated in BHIS with or without supplement. Germination was expressed as the loss of spore OD600. A) Loss of OD600 of spores of C. difficile isolates incubated in BHIS supplemented with 0.1% (w/v) taurocholate and 2 mM chenodeoxycholate. ▴, DH1834; ▾, 5108111; •, 9001966; ▵, 26131; ○, 7004578; ◊, CD 2315; and ▿, CDC38. The dotted line represents the loss of OD600 of the positive control strain (05-1223-046) in response to BHIS supplemented with 0.1% (w/v) taurocholate alone. B) Loss of OD600 of spores of C. difficile isolates incubated with BHIS supplemented with 0.1% (w/v) taurocholate. ▴, DH1834; ▾, 5108111; •, DH1432; ▵ 05-1223-046; □, CD 2315; ▿, CDC 38; and ○, DH1858. The dotted line represents the negative control strain (DH361) during incubation with both 0.1% (w/v) taurocholate and 2 mM chenodeoxycholate (a strain found, in preliminary studies, not to germinate when exposed to chenodeoxycholate). C) Loss of OD600 of spores of C. difficile isolates incubated with BHIS alone. ▴, DH1834; ▾, 5108111; •, 8085054; ▵, 05-1223-046; ○, 26173; and ▿, CDC38. The dotted line represents the loss of OD600 of the positive control strain (05-1223-046) in response to BHIS supplemented with 0.1% (w/v) taurocholate alone. All data represent the average of three independent experiments and error bars indicate the standard errors of the means.