Dogs were divided into three groups of five each: group 1, 90% proximal gastrectomy resulting in achlorhydria; group 2, division of the celiac and hepatic branches of the vagal nerves (the vagal innervation to the stomach remained intact); and group 3, truncal vagotomy and antrectomy.
Intestinal content obtained from the stomach, the duodenum, the jejunum, and the ileum by direct needle aspiration at the initial operation and four weeks later was cultured aerobically and anaerobically in nine media. Significant increases in the concentration of coliforms occurred in the achlorhydric animals (groups 1 and 3); clostridia also increased significantly in concentration in group 3 animals. The celiac and hepatic vagotomy operation (group 2) caused no change in the microflora.
Results of these experiments suggest that gastric acid is more important than vagal factors in regulation of the microflora of the upper gastrointestinal tract.
Broido PW, Gorbach SL, Condon RE, Nyhus LM. Upper Intestinal Microfloral ControlEffects of Gastric Acid and Vagal Denervation on Bacterial Concentrations. Arch Surg. 1973;106(1):90-93. doi:10.1001/archsurg.1973.01350130088020