J Clin Pathol Qual Control.  1999 Dec;21(2):301-307.

The Hematologic Interpretation of Blood Cultures Growing Staphylococci in Neonates

• Won DI
• Uh Y
• Kim KS
• Yoon KJ
• Seo DM

Abstract

BACKGROUND: Coagulase-negative staphylococci (CNS) represent the most common cause of serious nosocomial infection in many neonatal intensive care units (NICU). However, these organisms are also common contaminants of blood culture. It is a difficult problem to distinguish sepsis from culture contamination with blood cultures growing CNS.
METHODS
To determine the clinical significance of blood cultures growing staphylococci with hematologic findings, we have reviewed microbiological and hematological data obtained from 1,298 infants in our NICU who had bacteremia workup during a 3-year period. The 33 infants with two or more blood cultures positive for CNS were classified into 3 groups (with identical antibiotypes by disc diffusion method, with distinct antibiotypes, and resistant to 6 or more antibiotics).
RESULTS
CNS were the most frequently isolated organisms for which 98 (68%) of 144 infants had positive blood cultures. WBC count (p<0.05), absolute neutrophil count (ANC) (p<0.001) and neutrophil percentage (p<0.0001) of infants with positive blood cultures were significantly different between Staphylococcus aureus and CNS. There were no significant differences in WBC count. ANC and neutrophil percentage among 3 groups with two or more positive blood cultures and infants with one positive blood culture for CNS (p>0.05).
CONCLUSIONS
The results of ANC and neutrophil percentage supported the presumption of growing Staphylococcus as either S. aureus or CNS. The guidelines that are commonly used for distinguishing pathogens from contaminants with blood cultures growing CNS should be more strictly followed and the results obtained from the guideline should be interpreted with clinical assessments.

MeSH Terms

Bacteremia
Cross Infection
Diffusion
Humans
Infant
Infant, Newborn*
Intensive Care Units, Neonatal
Neutrophils
Sepsis
Staphylococcus
Staphylococcus aureus