Coagulase-negative staphylococcal skin carriage among neonatal intensive care unit personnel: from population to infection

Abstract

Coagulase-negative staphylococci (CoNS) are a major cause of sepsis in neonatal intensive care units (NICU) worldwide. Infecting strains of these commensal bacteria may originate from NICU personnel. Therefore, we studied the characteristics of CoNS isolates from NICU personnel and compared them to those of isolates from the general population and from sepsis patients. Furthermore, we studied the epidemiological effect on CoNS carriage of NICU personnel after a period of absence. In our study, we isolated CoNS from the thumbs of NICU personnel every 2 weeks during the summer of 2005 and sampled personnel returning from vacation and a control group from the general population. Furthermore, we collected sepsis isolates from this period. Isolates were tested for antibiotic resistance, mecA and icaA carriage, biofilm production, and genetic relatedness. We found that mecA and icaA carriage as well as penicillin, oxacillin, and gentamicin resistance were significantly more prevalent in CoNS strains from NICU personnel than in community isolates. Similar trends were observed when postvacation strains were compared to prevacation strains. Furthermore, genetic analysis showed that 90% of the blood isolates were closely related to strains found on the hands of NICU personnel. Our findings revealed that CoNS carried by NICU personnel differ from those in the general population. Hospital strains are replaced by community CoNS after a period of absence. NICU personnel are a likely cause for the cross-contamination of virulent CoNS that originate from the NICU to patients.

FIG. 1.

Bacterial species distribution among the different study populations.

FIG. 2.

Incidence of mecA- and icaA-containing and biofilm-producing strains among the different study populations. *, P < 0.05; **, P < 0.001.

FIG. 3.

Example of several RFEL gel patterns. (A) S. epidermidis ATCC 12228 control strain; (B) S. epidermidis blood isolate; (C) S. epidermidis prevacation isolate identical to that shown in panel B; (D) S. epidermidis prevacation isolate closely related to that shown in panel B; (E) unrelated S. epidermidis postvacation isolate; (F) unrelated S. warneri postvacation isolate.