Development of gut colonisation in pre-term neonates.

Twenty-eight pre-term babies of low birth weight were monitored for developing microflora in throat, stomach and faeces during the first 3 weeks of life. The flora at all levels of the gastrointestinal tract differed from that of healthy breast-fed and artificially fed full-term babies. Colonisation of throat and stomach was delayed beyond 4 days of life in 87% and 60% of babies respectively. Only 10% of babies had "normal" oral flora throughout the period of study. Flora of the stomach was sparse, and resembled faecal flora. Faecal flora was established more rapidly than throat or stomach flora, and 70% of babies were colonised during the first 4 days of life. Initially Bacteroides spp. were predominant (57% babies), but Escherichia coli and other aerobic gram-negative bacilli gradually increased in frequency. Colonisation by gram-positive bacteria was slow. Clostridium spp. were present in only 10% of babies during the first 4 days of life. Most strains were transient. Colonisation with C. butyricum (30%), C. perfringens (35%) and C. difficile (25%) was maximum after the first 2 weeks of life. Lactic-acid-producing bacteria usually appeared late in the third week of life. Parenteral feeding immediately after birth was associated with delayed colonisation by a restricted number of species. Parenteral antibiotics (penicillin or gentamicin or both) restricted colonisation with normal oral flora, the lactic-acid-producing bacteria and penicillin-sensitive clostridia, but had little effect on E. coli even when the colonising strain was sensitive to the aminoglycoside in the regimen. Systemic spread of bacteria via the blood stream was not detected in any babies. The pattern of colonisation of the enteric tract in pre-term infants in the special-care nursery studied, differs from that of healthy full-term babies; this merits consideration when the results of bacteriological tests of this vulnerable group of infants are being interpreted.