Bacterial populations adherent to the mucosa of the proximal colons of weaned, healthy pigs were compared with populations from pigs with dysentery induced by inoculation with a culture of Treponema hyodysenteriae. Isolates (136) representative of the predominant flora adherent to colonic epithelia of normal pigs and isolates (162) from pigs with dysentery were cultured anaerobically on a rumen fluid-based medium and characterized. Most (71%) of the isolates from colonic epithelia of normal pigs were gram positive, whereas 88% of the epithelia-associated isolates from pigs with dysentery were gram negative. The geometric mean of colony counts was 5.7 x 107/cm2 of colonic tissue from three normal pigs and 7.7 x 108/cm2 from four pigs with dysentery. A number of isolates obtained from contents of the lumens of normal pigs and pigs with dysentery were also characterized. Comparison of isolates from epithelial tissue and from contents of the lumens of the same pig indicated that these populations were different. Our results indicate that physiological changes that occur in the colons of pigs with dysentery are accompanied by marked changes in the microbial populations in the colons. The factors which regulate the population changes are not yet understood.

One hundred ninety-two isolates from cecal contents of three normal weaned pigs were obtained by means of anaerobic roll tube methods and were characterized. Seventy-eight percent of the isolates were gram-negative. The most numerous species isolated from each of the pigs was Bacteroides ruminicola. This species accounted for 35% of the isolates that were characterized, and Selenomonas ruminantium accounted for 21% of the isolates. Other gram-negative bacteria isolated from all three pigs were Butyrivibrio fibrisolvens (6.0%) and Bacteroides uniformis (3.0%); predominant gram-positive isolates were Lactobacillus acidophilus (7.6%), Peptostreptococcus productus (3.0%), and Eubacterium aerofaciens (2.5%). The other 42 isolates were placed in 14 other species, and 5 additional isolates that did not fit well into existing species were not placed taxonomically. Fifteen of the isolates (representing nine species) produced urease.

Concentrations of bacteria in the ceca and colons of pigs were measured by determinations of colony counts on rumen fluid-based media in anaerobic roll tubes. With our most complete medium (medium CCA), the mean colony count of cecal samples from 20 pigs was 2.37 x 10'°± 1.0 x 1010 (± standard deviation)/ g (wet weight). The mean number of bacteria attached to or associated with cecal epithelial tissues from three pigs on medium CCA was 2.67 x 107 ± 0.81 x 107/ cm2 of tissue. The proportions of gut bacterial populations able to use various energy substrates were estimated on the basis of relative colony counts. The following substrates are listed in descending order of their capacity to support growth of cecal bacteria: glucose, starch, cellobiose, xylose, Trypticase, gastric mucin from swine, mannitol, glycerol, and lactate. The effect of diet upon this distribution was not examined. The relative proportions of bacteria from a given population that were able to grow on various selective media were used as population profiles. Comparisons of populations in this way indicated that differences could be detected between (i) populations from the cecum of littermate pigs, (ii) populations from the cecum and colon of the same pig, and (iii) populations in the lumen of the cecum as compared with populations associated with cecal mucosa.

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A neutral volatile substance in ruminal contents from sheep suffering from acute indigestion due to overfeeding has been identified as ethanol. Ethanol was consistently observed in ruminal material from both cattle and sheep after they had been fed large amounts of readily fermentable carbohydrate.