Background Multi-resistant Staphylococcus capitis NRCS-A is involved in late-onset sepsis (LOS) in French NICUs.

Aims To investigate the geographical distribution of NRCS-A, and to precise its susceptibility profile.

Methods Twelve S. capitis isolates from distant NICUs (Australia, Belgium, France, United Kingdom, n = 3 each) and 2 S. capitis isolates from adult patients were analysed using PFGE, SCCmec typing, dru-typing, a MLST-like analysis, and antimicrobial susceptibility testing. To explore impact of vancomycin selective pressure, after 15 daily subcultures with vancomycin, we determined vancomycin, daptomycin and linezolid minimal inhibitory concentrations (MICs).

Results All NICU S. capitis (i) shared >80% similarity of PFGE profile and were similar to NRCS-A profile, (ii) harboured a type V-related SCCmec element, (iii) exhibited the same dru-type, (iv) formed a monophyletic group, (v) harboured a same antimicrobial susceptibility profile including aminoglycosides and methicillin resistance, and vancomycin heteroresistance. These molecular and antimicrobial susceptibility profiles differed from those of adult isolates. An increase of vancomycin and daptomycin (but not linezolid) MICs was observed, significantly faster (p < 0.05) for NRCS-A isolates than other tested strains.

Conclusion Our analysis demonstrates an unexpected worldwide distribution of S. capitis NRCS-A, specifically in NICUs. Recently, we collected complementary NICU isolates belonging to NRCS-A from Norway, Denmark, the Netherlands, USA, Brazil, New Zealand and Canada, confirming the worrisome dissemination of NRCS-A. Its multi-resistant profile and its ability to rapidly adapt to vancomycin selective pressure, constitute a selective advantage to NRCS-A in NICUs, and raise the issue of potential therapeutic failure and the need for alternative antimicrobial regimens.