Colonization and infection of mothers and neonates with group B streptococci in three Italian hospitals.

In the absence of previous published studies from Italy on the epidemiology of group B streptococci we investigated 1516 mothers at delivery and 1294 neonates in three hospitals. Of mothers in labour, 7.5% were colonized with group B streptococci and 4.9% of their babies. Of the neonates born to a positive mother 45.1% were colonized, whilst only 2.2% of babies born to a negative mother were colonized. For the mothers, the vagina was colonized more often (7.3% of all women) than the cervix (6.0%), the urethral meatus (3.9%) or the rectum (2.9%). For the neonates, the rates of colonization of the throat, external auditory canal, and the umbilicus were 3.2%, 3.0% and 2.6%, respectively. The distributions of the serotypes were similar to that reported from other parts of Europe and the USA and vertical transmission of group B streptococci was demonstrated in most of the mothers and their neonates. Of 30 mother-neonate pairs, 25% of mothers carried group B streptococci intermittently and 58% had persistent carriage until the 90th day postpartum, the rectum being the commonest positive site. Of 20 infants that were positive at birth, only six were still positive on the 15th day and none by the 90th day of life. Of 1294 infants, four (0.3%) developed early-onset sepsis with group B streptococci and one died. The overall incidence of clinical infection amongst colonized infants was 6.2%.