Influence of Gastric Acidity upon Viability of Bacteria in Isolated Stomach

Abstract

Johnson and Arnold 1 in a series of experiments on dogs with a non-leaking gastric fistula have found that exogenous bacteria (B. prodigiosus) lose their viability in the presence of free hydrochloric acid and when the gastric contents were alkalinized with Na₂HPO₄ buffer solution these previously non-viable exogenous bacteria regained their viability. This phenomenon was so constant that we decided to set up acute experiments in which we could entirely separate the stomach from the duodenum. By this technic we could completely exclude the possibility of any regurgitation from the intestine.

The experiments on dogs were conducted in the following manner. The abdomen of an animal, under nembutal anesthesia (1 cc. of 3% solution per kilo intraperitonealy), was opened and the pyloric part of the stomach with the duodenum brought up to the surface. A series of ligatures was put around the pyloric end of the duodenum through the wall of the duodenum to avoid a hemorrhage into the stomach and then the duodenum was severed about 1 cm. below the ligatures. In such a manner we produced a wide and non-bleeding opening into the stomach which facilitated the securing of specimens from the gastric contents. All the specimens were taken by sterile Wright pipettes.

First, we determined the pH (LaMotte hydrogen-ion testing set) of the gastric contents, then introduced into the stomach a suspension of B. prodigiosus (washings of a 24-hour growth on agar plate in 20 cc. sodium chloride solution) and simultaneously injected 1.5 mg. of a histamine intravenously. At certain time intervals (see chart) a specimen from the stomach was taken and tested for pH and for the presence of viable B. prodigiosus (one drop of the stomach contents spread on an agar plate, readings in 24 hours).