Studies on Streptococci: I. Distribution of Fecal Streptococci in Man

Abstract

To understand the significance to the host of streptococci as part of the intestinal microflora, we first tried to investigate the distribution of human fecal streptococci on the species level. Of the selective media compared, KMN agar was more effective than the other media for the isolation of streptococci from human feces. We made an effort to improve streptococcal classification. Especially we used utilization of 1% pyruvate, 1% arginine, and 1% citrate for differentiation between Streptococcus faecalis and S. faecium. In a tellurite tolerance test, S. faecalis was distinguished more clearly from S. faecium in the medium containing 0.16 or 0.32% tellurite. We devised methods of presumptive identification of fecal streptococci from the results of the characteristics of 1,442 isolates. These methods enabled us to identify many strains rapidly. Different results in the distribution of species of streptococci between children and adults were observed. S. faecalis and S. faecium were isolated constantly from both groups. S. bovis and S. avium were isolated frequently from the feces of children. On the other hand, "viridans" streptococci, e.g. S. salivarius, S. mitis and S. MG-intermedius were present at a high frequency in, and no S. avium could be isolated from, the feces of adults.

Salivaricin D, a Novel Intrinsically Trypsin-Resistant Lantibiotic from Streptococcus salivarius 5M6c Isolated from a Healthy Infant

“…Although S. salivarius is predominantly found in the human oral cavity (23,40), it has also been occasionally isolated from the gut (25,33,35,51), and salivaricin D is produced by a strain which was isolated from the feces of a healthy human infant, indicating that it forms part of the normal flora in the gut as well. In addition, the producer strain appears to occur in high numbers in fecal microflora, suggesting that it might have traits that make it competitive and dominant in the gut flora.…”

Survival of Yogurt Bacteria in the Human Gut

“…Isolates that were confirmed to be S. thermophilus isolates were then analyzed by pulsed-field gel electrophoresis (PFGE) because of the lack of reliable PCR primers that could distinguish between the closely related species S. thermophilus and Streptococcus salivarius present in human oral cavity (28,34). Profiles of SmaI-digested chromosomes, obtained as described by O'Sullivan and Fitzgerald (25), were compared in order to determine strain identities.…”

Studies on Streptococci

“…The isolation procedures for bifidobacteria were carried out under oxygen-free conditions. Streptococcal species were identified by the methods previously reported (18). Lactobacillus species were identified by microscopic observation, growth under aerobic conditions, gas production, fermentation of sugars (sorbitol, amygdalin, and melibiose), and growth at 45 C (8).…”

“…The homogenate was similarly diluted. Viable streptococci, lactobacilli, and bifidobacteria in appropriate dilutions of the contents and the tissue-homogenates were counted by inoculating portions of the dilutions on KMN and SF agar (18), LBS agar (11), and MPN agar (17). The isolation procedures for bifidobacteria were carried out under oxygen-free conditions.…”

“…We also reported that adhesion of lactobacilli to gastric epithelial cells of rats may be an important factor in colonization of the bacteria in the region, that the adhesion may be host specific, and further that some in vitro conditions influence the adhering ability (7,15). Recently, we reported the distribution of fecal streptococci in man (18). We think that streptococci are more important members of the lactic acid bacteria than lactobacilli because streptococci are present at a higher population level in the human ileum and large intestine (9,10).…”