The difference between bacterial dysentery and ulcerative colitis is mainly due to the following: 1. Bacterial dysentery is an infectious disease caused by Bacillus dysenteriae, which is highly contagious, whereas ulcerative colitis is non-infectious. 2. Bacterial dysentery is caused by the consumption of unhygienic and unclean food, with acute attacks, quicker onset and shorter duration of illness. 3.