Outbreaks of late-onset Group B Streptococcus (GBS) are rare. In February 2017, our 20 bed Neonatal Intensive Care Unit (NICU) identified 2 preterm infants with late-onset GBS infections occurring within a 5 day period, prompting an outbreak investigation and report of a probable link.
A case was defined as culture-confirmed invasive GBS in preterm infants <37 weeks gestational age. The first case of bacteremia due to GBS was identified in a 34 6/7 weeks infant born by caesarian section to a mother with unknown GBS status. The second case of bacteremia and meningitis occurred on a 27 5/7 weeks infant born by vaginal delivery to a GBS negative mother. Control measures included contact precautions, directed focus on hand hygiene, and cleaning of reusable equipment. Breast milk handling and storage were reviewed. Breast milk for the affected infants was stored in a separate refrigerator. Clean sweep cleaning of the unit focusing on high touch areas was done and adenosine triphosphate was used to identify organic matter on cleaned surfaces.
Analysis of the antibiogram showed that the GBS strain from the 2 infants had the same susceptibility patterns. Both strains displayed resistance to Erythromycin and sensitivity to Clindamycin. Pulsed-field gel electrophoresis confirmed that the isolates had an indistinguishable pattern and considered to be the same strain. Contact precautions were maintained until repeat cultures were negative and antibiotics were completed. There were no breaks in breast milk storage protocol and no additional cases were detected.
No environmental factor or clear mode of transmission were identified. However, horizontal transmission was highly suspected. The average NICU census during this time was 27, exceeding the maximum of 20 patients. High census and possible transient hand carriage of GBS by the staff may have played a role in the transmission of GBS. Adherence to hand hygiene and isolation practices were essential in containing the outbreak and preventing further transmissions.
K. Woods, None
E. Sordillo, None