Microbial colonization of tumors in relation to the upper gastrointestinal tract in patients with gastric carcinoma.

The microbial colonization of the oropharynx, the esophagus, the stomach, and the duodenum was studied in relation to the microbial flora found on tumor and gastric mucosal biopsies in 23 patients with gastric carcinoma. The tumor was colonized in all patients, and the stomach, the esophagus, the duodenum, and the gastric mucosa were colonized in 96%, 87%, 83%, and 78% of the patients, respectively. The most common microorganisms isolated were streptococci, bifidobacteria, lactobacilli, and Bacteroides species, belonging to the normal oropharyngeal flora. Microbial colonization with gram-negative rods, Clostridium species or yeasts, was present in at least one site in 91% of the patients. Clostridium species were isolated from 57% of the patients. The total numbers of microorganisms recovered from the tumor biopsies did not vary with the intraluminal gastric pH. A relation between the gastric pH and the total number of microorganisms in the gastric juice existed. Significant higher numbers of different strains of microorganisms (p less than 0.005) colonized the tumor compared to the gastric mucosa. Anaerobic microorganisms colonized the tumor significantly more often than the mucosa (p less than 0.001). Antibiotic agents used as prophylaxis in gastric cancer surgery should cover both aerobic and anaerobic microorganisms, including B. fragilis.