Importance of the environment and the faecal flora of infants, nursing staff and parents as sources of gram-negative bacteria colonizing newborns in three neonatal wards.

Gram-negative bacteria are an important cause of invasive infection among neonates. In this study a novel fingerprinting method was used for the first time to assess the importance of various potential reservoirs of the major gram-negative enterobacteria that colonized 46 consecutive infants in three neonatal special care units during a three to four week period. Such bacteria were isolated from the oropharynx, umbilical cord and faeces in 24%, 33% and 100% of the infants, respectively. Klebsiella/Enterobacter spp. dominated over Escherichia coli and spreading (shared) over sporadic strains. Sixty-one percent of the neonates were colonized with at least one and up to six different strains shown to exist in the ward, mainly in other infants. Environmental reservoirs and the faecal flora of mothers and staff were of minor importance. Vertical transmission occurred in 12% of vaginally delivered infants and in 0% of those delivered by caesarean section.