Harbouring group B streptococci in a neonatal intensive care unit led to an outbreak among preterm infants.

We report a nosocomial outbreak with group B streptococci (GBS) in a level two neonatal intensive care unit (NICU) at Sachs' Children and Youth Hospital, Stockholm, Sweden, in 2014. There were five very preterm infants with severe late-onset septicaemia, and 10 further infants were colonised. Pulsed-field gel electrophoresis and multilocus sequence typing genetic characterisation showed that one GBS strain was the cause: serotype Ia, sequence type 23, clonal complex 23. The NICU environment cultures revealed GBS reservoirs on surfaces near sick and colonised patients. We identified workflows and guidelines that could increase the risks of nosocomial infections. Conclusion: This nosocomial GBS outbreak among preterm infants demonstrates that GBS can be harboured in the NICU environment.