Neonatal infection with Staphylococcus capitis NRCS-A in Iceland: A 12-year longitudinal, retrospective study of strains from patients, staff and the environment in a neonatal intensive care unit.

BACKGROUND

The multidrug resistant NRCS-A clone of Staphylococcus capitis (SC) has spread globally in neonatal intensive care units (NICUs) where it causes neonatal sepsis and colonisation of infants, fomites and staff. Whole genome sequencing (WGS) of international isolates has suggested a putative origin of the clone in Norway, which is closely related to Iceland geopolitically. No data have been available about the NRCS-A clone in Iceland where a case of neonatal sepsis in 2014 suggested its presence for the first time. This study examines the epidemiology of the clone in the single Icelandic NICU over a 12-year period and its relationship to international isolates.

METHODS

The study involved retrospective examination of the occurrence and clinical significance of SC-NRCS-A isolated from blood cultures of infants during 2009 - 2020, and prospective screening for SC among infants, staff and the environment. WGS was done on selected isolates to verify the presence of the SC-NRCS-A clone, examine phylogenetic relationship within the Icelandic isolates, and compare them with an international collection of SC-NRCS-A.

RESULTS

SC-NRCS-A was found in blood cultures from 28 infants, of which nine with sepsis, and was a frequent coloniser of infants and diverse fomites. In staff SC-NRCS-A was detected in nares, throat and scalp. WGS of 93 isolates from blood and prospective screening specimens and comparison with international isolates revealed that the Icelandic SC-NRCS-A was distributed into two clusters, one related to Norwegian and the other to Irish SC-NRCS-A isolates. Both clusters contained isolates representing all sample sources.

CONCLUSION

The study demonstrated interpatient transmission, widespread dissemination and persistence of the SC-NRCS-A clone in the Icelandic NICU. The close phylogenetic relationship of Icelandic isolates with those from Norway and Ireland suggests potential import to Iceland by NICU staff or infants receiving medical care in these neighbouring countries at some point before 2009 for the Irish clone and before 2014 for the Norwegian clone.