Genetic population structure of coagulase-negative staphylococci associated with carriage and disease in preterm infants

Coagulase-negative staphylococci (CoNS) are a leading cause of sepsis in th e neonatal intensive care unit (NICU) setting. To evaluate the hypothesis t hat isolates of CoNS associated with disease belong to hypervirulent clones , as opposed to being drawn randomly from the neonatal unit carriage flora, we conducted a prospective, case-controlled study in a busy NICU. Using pu lsed-field gel electrophoresis (PFGE), we compared the population structure s of CoNS isolates associated with bacteremia with isolates from the skin o f healthy and infected neonates and with blood culture contaminants. Endemi c clones of CoNS were identified, but there was no difference in the distri bution of the 6 species or 73 PFGE types between the carriage and disease i solate groups; this suggests that hypervirulent clones with an enhanced abi lity to cause disease were not present in this NICU setting.