Late-onset group B streptococcus infection in a preterm neonate

Early-onset group B streptococcus (GBS) is transmitted vertically from the birth canal of colonized mothers. The mode of transmission of late-onset GBS is less clear, although it is believed to reflect a delayed infection after early colonization from either vertical or horizontal transmission. We present a premature female infant whose mother was GBS negative at the time of delivery but later had GBS bacteriuria in postpartum. The infant had an initial blood culture and multiple weekly nasal surveillance cultures that were all negative for GBS. The infant's nasal culture grew GBS after 25 days, 1 day after she had signs of sepsis and her blood grew GBS. This is the first case in preterm infants to demonstrate the horizontal transmission of late-onset GBS bacteremia without the need for early-onset colonization.