ABSTRACT
This chapter discusses the various methods used to obtain and to culture samples from the upper gastrointestinal tract and describes the various factors responsible for the control of the microflora. It reviews the microflora at the various subsites to be considered together with the evidence on the mechanisms of acquisition, development and retention of the microflora. The major factors controlling the microflora of the upper gastrointestinal tract are the age and diet of the patient, the pH and physiology of the subsite, the mobility of the gut, host-microbe interactions, and microbe-microbe interactions. The effect of diet on the microflora is due both to the bacteria present in the food and to the effect of diet on the resident microflora at any site. The upper digestive tract in young healthy Western adults is essentially free from bacteria because of the sterilizing effect of gastric acid.
