Relationship between gastric secretion and infection.

Abstract

Progress report Relationship between gastric secretion and infectionWhy does the stomach secrete acid?Animal stomachs are specialised organs which produce a highly acidic secretion.This is found in a wide spectrum of animals from fish to mammals.In man, acid secretion is not essential for life, or indeed for adequate digestion, as evidenced by the continued survival of achlorhydric patients with pernicious anaemia.The physiological role of gastric acid may be summarised as follows:-(1) The initiation of protein digestion through the activation of pepsinogen.(2) The augmentation of dietary calcium and iron absorption.(3) The defence of the highly specialised absorptive and secretory cells of the lower alimentary tract from ingested organisms.This review will concentrate on the role that gastric acid plays in the protection against ingested organisms, as well as considering the possible effects of infection on gastric secretion. Protective role of gastric acidInterest in this area has recently been renewed.'The low pH of the intragastric environment constitutes one of the major non-specific defence mechansims of the body.Reduction of gastric acid secretion predisposes to infection with a variety of organisms including those responsible for typhoid and non-typhoid salmonellosis,2 3 bacillary dysentery,4 cholera,5 6 brucellosis,7 giardiasis8 and strongyloidiasis.3In addition, there are isolated reports to suggest that Clostridium difficile infection leading to pseudomembranous colitis,9 and infection with the fish tapeworm Diphyllobothrium latum3 are more likely in association with hypochlorhydria.The protective role of gastric acidity is further emphasised by consider- ing infection with Salmonella and the cholera bacillus.It is well recognised that previous gastric sur iery is a significant risk factor for the development of Salmonella infection.° l This is directly related to reduction in gastric acid secretion.Elderly patients are more likely to incur severe infection with Salmonella,12 which is probably related to the reduction in gastric acid secretion after the age of 60.13 4 Cholera bacilli are markedly acid sensitive.15Infection is more likely to occur, and to be more severe in association with reduced acid secretion.'6Bacteria introduced into the stomach are destroyed within 15 minutes when the pH is 3*0 or below,'7 but gastric juice retains some effective bactericidal activity up to pH 4*0.The bactericidal properties of gastric juice are principally because of the low pH.17 18 The bacterial count in the stomach is normally much less than 96 on