Development of the Normal Intestinal Flora and Clinical Significance in Infants and Children

We studied development of bacterial flora in the stool in breast-fed and bottlefed infants. Subjects and methods. Stools of 13 healthy newborn infants (six were breast-fed and seven were bottle-fed) were cultured. Stool samples were taken daily for six days after birth. Another culture was performed at one and three months of age, as the infants returned to the Well-Baby Clinic for a routine check-up. The stool was obtained directly from the rectum using a glass tube with rounded top and a side hole. The culture was performed within two hours of stool collection. A series of media were employed for anaerobic culture. Viande et de Levures medium with 0.2% glucose (VLG) was used for total bacterial count, VLG medium containing 7.5 ƒÊg/ml of vancomycin and 5 ƒÊg/ml of gentamicin for Bacteroides spp., and a modified Petuely's selective medium with nalidixic acid (MPN) was used for bifidobacteria (1). These media were prepared in test tubes with tight stoppers under "pre-reduced anaerobically sterilized" conditions. Procedures of anaerobic sample preparation and culture were performed by the method described by Holdeman et al (2). Air in the media and culture tubes was always substituted with CO2 using a CO2-gas stream. All cultures were done quantitatively and grown colonies were read and counted. Results. Changes in the count of organisms for individual bacterial groups are shown in Fig. 1 (3, 4). The count is described in terms of common logarithms of the bacterial count per g of feces (for example, a bacterial count of 108 per g of feces is expressed as log 8/g). On the day after birth, a mean organism total of log 9.0•}1.1/g of feces was measured. Enterobacteria were the predominant organism, followed by smaller numbers of enterococci, staphylococci, and Bacteroides. The number of entero-