Antibacterial activity detected in duodenal juice

Antibacterial activity could be detected in bacterium-negative duodenal juice from 3 patients, whereas it was not detected in bacterium-positive duodenal juice from other 3 patients. The follow-up study revealed that appearance of the activity in duodenal juice was just coincident with disappearance of bacteria in duodenal juice. The activity was not influenced by pH of the duodenal juice. These results seem to suggest that some antibacterial activity, different from that of pH, in duodenal juice regulates in some way proliferation of the upper gastrointestinal flora.