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BACKGROUND: In February 2015, the North Carolina Division of Public Health was notified of 4 late-onset Group B streptococcal (LO GBS) infections among infants in a neonatal intensive care unit (NICU). Reported outbreaks of LO GBS are uncommon. We investigated to identify cases and prevent additional infections.
METHODS: We defined a case of LO GBS infection as isolation of Group B Streptococcusfrom a clinical specimen obtained on or after January 1, 2015 from a normally sterile site in a patient aged ≥7 days who was present in the NICU at symptom onset. We conducted a site visit to observe infection control practices and review medical information of cases and non-cases. We compared clinical and demographic features between cases and non-cases and determined prevalence of infant GBS colonization in the NICU by collecting surface swabs from all infants present on February 6, 2015. We performed serotyping on available GBS isolates and multilocus sequence typing (MLST) on a subset of isolates.
RESULTS: We identified four cases of LO GBS infections. Onsets ranged from January 15–February 1, 2015. Cases had lower birth weights (median 953 grams versus 2480 grams) and earlier gestational ages (median 27.5 weeks versus 35 weeks) than non-cases. Of 46 infants screened, 11 (24%) were colonized with GBS; 3 (27%) of these 11 were also case-patients. GBS-colonized and -infected infants were geographically clustered within the NICU. Among the isolates tested, GBS serotypes III, 1b, and Vwere identified, with serotype III being most common (8/11, 73%). MLST conducted on the type III isolates identified patterns ST19 (7 isolates) and ST8 (1 isolate). We identified several infection control breaches, including inadequate hand hygiene between contact with infants and their environment. A review of mothers’ GBS status among cases found that one was identified as a GBS carrier during pregnancy and had not received appropriate antibiotic prophylaxis during delivery. After addressing infection control practices, cohorting infected and colonized infants by nursing staff and geographic location, screening of all new admissions, and weekly screening of cohorted infants until GBS-negative., no new cases have been identified.
CONCLUSIONS: This cluster of GBS infections in a NICU with a high prevalence of colonization and spatial clustering suggests nosocomial transmission and highlights the importance of strict adherence to infection control practices. The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.