FATAL EARLY-ONSET GROUP B STREPTOCOCCAL INFECTION WITH A NORMAL CBC

Abstract

Changes in blood neutrophil (neut) number and in degree of left shift are used as diagnostic clues when neonatal sepsis is suspected. However, we report a pitfall in reliance upon CBC changes. We observed 4 cases of fatal group B streptococcal (GBS) sepsis with a normal neut count (mean 7730;range 6140-9610) and a normal immature|total(i/t) neut ratio (0.04;0.00-0.09). In 2 cases this was used as a reason to withhold antibiotics. In 2, the CBC was repeated prior to death (0 and 150|mm³). In an animal model of lethal GBS infection, we determined the length of the "latent period" between bacterial inoculation and CBC changes. Neonatal and adult rats received GBS after which blood and marrow were serially examined. The neonates died by 24 hours, but no change in CBC occurred until after 4 hours when an increase in i|t ratio (0.40 ± 0.05, control vs 0.58±0.3 infected, mean±SEM, p<0.05) and a decrease in marrow neut (78±0.4% of control, p<0.05) was seen. In adult animals, CBC changes were evident after only one hour; i|t ratio increased from 0.25±0.05 to 0.52±0.04 (p<0.001) and marrow reserves dropped to 77 ± 3% of control, (p<0.05) consistent with rapid release of marrow neut. These experiments demonstrate a significant delay, in neonates, between bacterial inoculation and mobilization of storage neut. Therefore, CBC changes during infection are delayed. A normal CBC is expected during the first several hours of neonatal sepsis and antimicrobial therapy must not be withheld because the CBC is normal.

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