METHANOGENS IN THE HUMAN INTESTINAL-TRACT AND ORAL CAVITY

The incidence and concentration of methanobacteria in the human intest inal tract have not been well evaluated. Only recently were such micro organisms found in the oral cavity. We determined the counts of methan ogens in the feces of healthy subjects on a Mediterranean diet and eva luated whether individuals with methanobacteria in the intestine also harbor such bacteria in the oral cavity. Methanobacteria were observed in the feces of 18 of the 20 subjects, at a level ranging from 10(3) to 10(10)/g dry wt. Only 45% of the subjects harbored methanobacteria in the plaque and saliva, showing that the presence of methanogens in the oral cavity was not correlated with their presence in the feces. T he presence and number of methanobacteria appeared to remain constant after 3 months. A short rod arranged in chains, similar to the Methano brevibacter smithii which predominates in feces, was the methanogenic form present in the mouth.