Common symptoms of bacterial infection in stomach are: 1  Pain in stomach with cramps in the stomach. 2  Diarrhea. 3  Gastritis, with retrosternal burning and waterbrash. 4  Dark or black color of stool. 5  Cramps in abdomen.6  Stomach ulcer. 7  Aggravation of pain in stomach after intake of food. 8  Vomiting and nausea.9  Weight loss. 10  General feeling of tiredness. 11  Fever. Pain in stomach with cramps in the stomach. 2  Diarrhea. 3  Gastritis, with retrosternal burning and waterbrash. 4  Dark or black color of stool. 5  Cramps in abdomen. 6  Stomach ulcer. 7  Aggravation of pain in stomach after intake of food. 8  Vomiting and nausea. 9  Weight loss.