Direct isolation of coagulase-negative staphylococci from neonatal blood samples

Coagulase-negative staphylococci (CNS) were isolated by direct inoculation of anticoagulated whole blood onto agar from 14 (41.2%) of 34 episodes (30 neonates) of suspected bacterial infection, associated with isolation of CNS from the same blood sample by broth-dilution blood cultures. The equivalent of more than 1,000 cfu ml-1 were isolated from four samples (four neonates); the range of counts was 1-103 cfu 25 microliters-1. There was a statistically significant association between isolation of CNS by direct agar inoculation and a raised C-reactive protein level and/or a positive nitroblue tetrazolium test and with the use of an intravascular catheter when compared to those episodes where CNS were isolated from broth blood cultures only. This simple procedure provides an estimate of the number of CNS in the blood of a neonate with suspected bacteraemia and may help to corroborate a diagnosis of CNS bacteraemia.