Abstract
Fifty-five healthy, full-term babies were studied to determine the age at which methanogens establish as part of the developing intestinal microflora. The infants were stratified into diet groups according to whether they were fed breast milk, formula or formula supplemented with different amounts of an iron-binding protein. The faecal microflora, including methanogens, was enumerated at 1, 4, 8 and 12 wk of age. Methanogens colonised the infant intestine surprisingly rapidly. By 1 wk of age, 11 of 47 babies (23 per cent) had acquired methanogens and the proportion of infants colonised rose to 70 per cent, 86 per cent and 83 per cent at 4, 8 and 12 wk, respectively. Analysis of sequential samples from individual infants revealed that, once established, methanogens were rarely lost from the gut microflora. Diet did not appear to influence colonisation by methanogens directly. Acquisition of methanogens by I wk of age was associated with the equally early establishment of a relatively complex faecal microflora characterised by higher concentrations of bacteroides, clostridia and enterobacteria.