The development of the bacterial flora in normal neonates.

The development of the bacterial flora of neonates during the first week of life was studied in 23 babies. Specimens of meconium or faeces were collected and swabs taken from the umbilicus and mouth on days, 1, 2, 3 and 6. The bacteria present were isolated on a variety of plain and selective media. The predominant faecal organisms by the end of the first week were anaerobes. Bifidobacteria were isolated from all the neonates and bacteroides and clostridia were isolated from 78.3%. Bifidobacteria and bacteroides were present in large numbers; other species were isolated in smaller numbers. Enterococci were isolated from all neonates, enterobacteria from 82.6%, anaerobic cocci from 52.2%, and streptococci and staphylococci from 34.8% each. Staphylococcus aureus was the predominant species isolated from the umbilicus; it was isolated from 21.7% of neonates on the first day rising to 87.0% by the sixth day and represented 49% of isolates from this site. S. albus, streptococci, enterococci and Escherichia coli were each isolated from a few neonates. Viridans streptococci (31.4% of isolates) and Streptococcus salivarius (25.1%) were the commonest species recovered from the mouth. They were present from 8 h after birth; S. albus and Neisseria spp. were isolated later on the first day, and anaerobic species of Veillonella and Bifidobacterium appeared on the second day.