Nester's Microbiology 8th Edition by Denise Anderson,Sarah Salm,Deborah Allen

Exercise 1

The digestive tract is a complex ecosystem and a major route for pathogens to enter the body. Bacteria colonizing the tooth surface can create a biofilm called plaque. People with poor saliva production risk severe tooth decay. Infections of the esophagus are so unusual that their occurrence suggests immunodeficiency. The stomach stores food; acidic gastric fluid destroys most microbes before they reach the intestines. The small intestine carries out the majority of the digestion and absorption of nutrients. Undigested material becomes feces in the large intestine. Metabolic activity of intestinal microbiota produces vitamins, but it causes gas and can contribute to cancer. Disruption of the normal microbiota through antibiotic treatment can result in antibiotic-associated diarrhea.
What causes halitosis (bad breath)?