If you have bacterial gastroenteritis, bacteria have caused an infection in your gut. This usually results in your stomach and intestines becoming inflamed, and you’ll probably experience unpleasant symptoms such as vomiting, severe abdominal cramps and diarrhea.ymptoms. The symptoms you experience may vary according to the type of bacteria causing your infection, but they could include: 1  loss of appetite. 2  nausea and vomiting. 3  diarrhea. 4  abdominal pains and cramps. 5  blood in your stools. 6  fever.