The significance of Escherichia coli in the upper respiratory tract of children under 2 years of age.

Colonization of the upper respiratory tract of neonates by Gram-negative bacilli (especially Escherichia coli) is not rare, and the incidence declines after 1 year of age. It is believed that the likelihood of colonization increases with the length of stay in hospital at the time of birth, and that such colonization does not reflect any pathological process. Evidence has not been found to support the view that the use of antibiotics is the reason for colonization in neonates (the situation in adults or children over 2 years of age is not considered here). The authors believe that the birth canal is not an important source of Gram-negative bacillary flora but that perineal contact at birth and maternal handling after birth more probably are, especially in the hospital environment where Gram-positive organisms have been suppressed by hexachlorophane. With the limited range of E. coli typing sera available, a relatively high proportion of non-typeable strains was found. Among those which did type, the incidence of various strains corresponded fairly closely to those which are known to occur in the normal bowel and to cause urinary infections. No evidence for typespecific respiratory pathogenic strains was found.