Fig. 4
CD gene copy (GC) numbers and cytotoxin titers in TRs of model 2. a Period B and C in TR2-4. CD GC numbers and toxin titers are shown starting from first detection of CD growth in TR3 on day 7. TR1 was treated with CRO during period B and C but no CD growth was detected in this reactor during these periods. b Period D-F in TR1 and TR4. CD colonization was observed during period D. On day 21 metronidazole treatment [E] was performed in TR1 and TR4 for 10 days and followed by a recovery period [F] of 10 days. CD GC numbers and cytotoxin titer were determined by qPCR and Vero cell assays, respectively. (—) CD detection limit of 4.4 GC mL−1. CRO, ceftriaxone; CD, Clostridium difficile