SummaryFrom in-vitro studies of breast and cow's milk preparations, and of the faeces from breast-fed and bottle-fed infants, a number of factors seemed likely to influence the production and maintenance of a lactobacillary flora and low pH in the faeces of newborn infants. These were mainly attributable to the nature of the feed.

PLATE XXIV IT is well known that the nature of the milk fed to newborn 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. 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). VLG medium (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. Modified reinforced clostridial medium (RCM). This was the Oxoid CM 149 formulation (Oxoid Manual, 1973) from which soluble starch, sodium acetate, and agar were omitted. It formed the nutrient basis of acetate-bufFered RCM and unbuffered RCM. Acetate-buflered RCM. Modified Reinforced Clostridial Media buffered at nine different pH values over the range of 3.8-6.2 were prepared by adding the basic ingredients to aliquots

No abstract

No 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...