Bifidobacteria in the intestinal tract of infants: an in-vitro study

Abstract

IT is well known that the nature of the milk fed to new-born infants greatly influences the physico-chemical and microbiological properties of their faeces. The most prominent features of the faeces of breast-fed infants in comparison with those of bottle-fed infants are a preponderance of bifidobacteria, a low pH and a virtual absence of putrefactive organisms, and it has been customary to regard this triad as sequentially related.The results of studies in vivo indicate that although pH does influence the nature of the bacterial flora, of much greater importance in this respect is the presence of an acetic acid and acetate buffer (Willis et al., 1973;Bullen, Tearle and Willis, 1976).The aim of the present study was to determine the principal source of acetic acid in infant faeces and the effect of both acetic acid and of an acetic acid and acetate buffer on the growth of certain common faecal bacteria and enteric pathogens .MATERIALS AND METHOD Organisms. Bacteroides fragilis, two laboratory isolates; bifidobacteria, six laboratory, isolates; CZostridium paraputrificum, two laboratory isolates; Clostridium perfringens two laboratory isolates; Escherichia culi, six laboratory isolates including enteropathogenic serotypes 027, 01 11, 0125, 0126; Pseudomonas aeruginosa, strains NCTC 10662 and 10701 ; Salmonella typhimurium, two laboratory isolates ; Shigella sonnei, two laboratory isolates ; Streptococcus faecium, five laboratory isolates ; Vibrio cholerae biotype El Tor, one laboratory strain.The laboratory strains were isolated from the faeces of infants except for the strains of C. perfringens, Salm. typhimurium, Shig. sonnei and V. cholerae El Tor, which were isolated from older patients.Acetate buflers. A series of nine acetate buffers in the range of pH 3.8-6.2 were prepared as described by Cruickshank et al. (1975). (Beerens, et al., 1963). This fluid medium, which contains 1 % glucose, was used in 20-ml aliquots in Universal containers for the production of acetic acid by bacterial cultures. of each of the acetate buffers. The medium at each different pH value was dispensed in 15-ml volumes in Universal containers; the bottles were steamed once for 30 min. Unbufered RCM. Modified Reinforced Clostridial Media at the same pH values as the buffered media were prepared by dissolving the basic RCM ingredients in distilled water and adjusting the pH with glacial acetic acid. The medium at each of the nine different values was dispensed in 15-ml volumes in Universal containers; the bottles were steamed once for 30 min. VLG medium Modified reinforced clostridial medium (RCMAcetate-buffered RCM and unbuffered RCM media were used to study the effect of pH, of acetic acid and of acetate buffer on the growth of the various bacterial species.Determination of volatile products of bacterial metabolism. Strains of bifidobacteria, E. coli and Strept. faecium were examined for volatile products of metabolism. Five-day-old anaerobic cultures in VLG medium were extracted with 1.0 ml of di-ethyl ether before and after acidific...

Genomic Insights into Bifidobacteria

“…This hypothesis was tested by comparing the compositions of intestinal bacteria in the feces of breast-fed and formula-fed infants, and the proposed increase in bifidobacteria and concomitant decrease in undesirable microbes were observed (352). This inhibition effect by bifidobacteria was supported by fecal pH measurements, as the fecal pH of bottle-fed infants was found to be Ͼ7.0, and that of breast-fed infants was Ͻ6.0, during the first 7 weeks after birth (39). This is most likely due to the production of lactic and acetic acids by bifidobacteria.…”

“…In his pediatric work, he used bifidobacteria for the treatment of this intestinal diarrhea, and this likely represents the first example of the oral administration of a live microorganism for the treatment of a disease (316). The abundance of bifidobacteria in the feces of breast-fed infants was thought to be due to the Bifidobacterium-stimulating properties of human breast milk (38,46,60,96,196,321). Numerous studies have substantiated the higher bifidobacterial counts and lower incidences of gastroenteritis in breast-fed infants than in formula-fed infants (3,40,51,98).…”

“…These HMOs consist of short-chain trisaccharides, such as sialyllactose or fucosyllactose, and complex, high-molecularweight glycans, such as N-acetyllactosamine polymers (31). The stimulation of bifidobacteria by human breast milk, resulting in their prevalence in the gut, was proposed to be involved in the suppression of undesirable intestinal bacteria (38). This hypothesis was tested by comparing the compositions of intestinal bacteria in the feces of breast-fed and formula-fed infants, and the proposed increase in bifidobacteria and concomitant decrease in undesirable microbes were observed (352).…”

Genomic Characterization and Transcriptional Studies of the Starch-Utilizing Strain Bifidobacterium adolescentis 22L

“…During weaning, infants switch to a solid-food diet, being exposed for the first time to different (i.e., as opposed to those in mother's milk) complex carbohydrates. In infants, the lack of chewing ability, the very small amount of salivary amylase activity, and the immaturity of the infant's gut allow a large amount of such sugars, including starch, to escape digestion from the upper compartments of the gastrointestinal tract, thereby arriving in an essentially intact form in the large intestine of neonates (62 (50), and the proven ability of B. adolescentis 22L as an active degrader of resistant starch adds to this list of diet-polysaccharide users (7). …”

Response of Bifidobacterium Species to Growth Promoters in Human and Cow Milk

“…Bifidobacteria may contribute to this protective capacity by establishing an acetate buffer in the intestinal tract of the infant (8) that may inhibit potential pathogens (9) and thus enhance natural resistance to enteric infections.…”