Wide geographical dissemination of multiresistant Staphylococcus capitis NRCS-A clone in neonatal intensive care units

Nosocomial late-onset sepsis represents a frequent cause of morbidity and mortality in preterm neonates. The Staphylococcus capitis clone NRCS-A has been previously described as an emerging cause of nosocomial bacteremia in French neonatal intensive care units (NICUs). In this study, we aimed to explore the possible unrecognized dissemination of this clone on a larger geographical scale. One hundred methicillin-resistant S. capitis strains isolated from neonates (n=86) and adult patients (n=14), between 2000 and 2013 in 4 different countries (France, Belgium, UK and Australia), were analyzed by performing SmaI PFGE and dru typing. The vast majority of NICU strains presented NRCS-A pulsotype and dt11c type (96%). We then randomly selected 14 isolates (from neonates n=12, 3 per country, and adult patients n=2), considered as a subset of representative isolates, and performed further molecular typing methods (SacII PFGE, SCCmec typing and MLST-like analysis), confirming the clonality of the S. capitis strains isolated from neonates, despite their distant geographical origin. Whole genome SNP based phylogenetic analysis of 5 NICU isolates (from the different countries) attested to high genetic relatedness within the NRCS-A clone. Finally, all the NRCS-A strains exhibited multidrug-resistance (e.g., methicillin and aminoglycoside resistance, decreased vancomycin susceptibility) with potential therapeutic implications for infected neonates. In conclusion, this study represents the first report of clonal dissemination of a methicillin-resistant coagulase-negative staphylococcus on a large geographical scale. Questions remain regarding the origin and means of international spread, as well as the reasons for this clone's apparent predilection for neonates.