Background. Hospital outbreaks of invasive group B streptococcus (GBS) infection are rare. There are only a few published reports of late-onset GBS outbreaks in neonatal intensive care units (NICUs). We report here three cases of late-onset GBS in our NICU.

Case. Three preterm very low birth weight (VLBW) infants born at 24 -27 weeks gestation developed lateonset GBS sepsis within four weeks. Two asymptomatic GBS carriers were identified in the NICU prior to the outbreak. Tests of maternal rectovaginal GBS colonization were negative in all three cases; as such, vertical transmission was unlikely. All three GBS isolates were capsular serotype 1b, with comparable antibiotic susceptibility profiles.

Conclusion. Preterm delivery and VLBW are associated with an increased risk of invasive late-onset GBS infection. This report underscores the ongoing risk of nosocomial transmission of GBS in the NICU.

Keywords: Group B Streptococcus, NICU, outbreak, sepsis, very low birth weight infant