Differences of Microflora Depending on the Parts of Human Stool

Distribution of the fecal microflora in several specimens from different locations of the human stool was analyzed with the steel wool method and the plate-in-bottle method. Total bacterial counts and the number of bacteroidaceae at the upper portion of the stool were significantly higher than those at the lower portion by both culture methods. Lecithinase-negative clostridia were recovered in significantly higher numbers at the middle or upper portion compared with the lower portion by the plate-in-bottle method. The number of lactobacilli was significantly higher at the upper portion than at the other portions. There was no significant difference in the numbers of other bacterial groups observed. The percentage of bifidobacteria in the total bacterial populations enumerated by the steel wool method varied among the three portions of the stool, while those counted by the plate-in-bottle method were consistent. These results indicate that the composition of the fecal microflora was differently analyzed at the parts of the stool possibly because of oxygen diffused from the anus. A culture method for highly oxygen sensitive anaerobes could minimize this difference.