CAT and colitis: In the experiment where mice were pretreated with antibiotics prior to the administration of the engineered bacterium ECN‐pE(C/A)2, a diminished efficacy against colitis was observed, suggesting a significant association between intestinal flora and disease improvement.[61] Subsequent investigation revealed that ECN‐pE(C/A)2, producing SOD and CAT, enhanced the abundance and diversity of the flora and increased the levels of butyric acid‐producing probiotics, whereas unmodified EcN demonstrated did not significantly alter the gut flora.