Related Experiment Videos
Kinetics of phagocyte response to group B streptococcal infections in newborn rats
Insights
Neonates exhibit unique susceptibility to infection due to inadequate leukocyte mobilization. Their neutrophil response to group B streptococcus is insufficient, contributing to high mortality rates in newborns.
Area of Science:
- Immunology
- Neonatal Research
- Infectious Disease
Background:
- Neonates are uniquely susceptible to infections.
- The role of leukocyte mobilization in neonatal infection susceptibility is not fully understood.
Purpose of the Study:
- To investigate the kinetics of phagocyte response in neonatal and adult rats following intraperitoneal infection with group B Streptococcus, type Ia.
- To test the hypothesis that inadequate in vivo leukocyte mobilization contributes to neonatal infection susceptibility.
Main Methods:
- Comparative study of neonatal and adult rat responses to intraperitoneal infection with group B Streptococcus, type Ia.
- Quantification of peritoneal leukocytes (neutrophils and macrophages) and blood neutrophils over time.
- Assessment of bacterial clearance and bacteremia.
Main Results:
- Neonatal rats had a significantly lower 50% lethal dose of group B Streptococcus compared to adults.
- Leukocyte and neutrophil counts increased more slowly in neonates than in adults post-infection.
- Adults cleared bacteria more efficiently, while neonatal neutrophils decreased over time.
Conclusions:
- Neonatal neutrophil response to group B Streptococcus infection is inadequate.
- Impaired leukocyte mobilization in neonates may contribute to their increased susceptibility and mortality from infection.
Abstract:
To test the hypothesis that inadequate in vivo mobilization of leukocytes may contribute to the unique susceptibility of neonates to infection, we studied the kinetics of phagocyte response to neonatal and adult rats to intraperitoneal infection with group B streptococcus, type Ia. The 50% lethal dose was considerably greater for adults than for neonates (1.1 x 10(7) colony-forming units per g versus 2.7 x 10(2) colony-forming units per g). After challenge with group B streptococcus, type Ia, the number of neonatal peritoneal leukocytes increased more slowly than did those of adult rats. For example, at 4 h, the adult neutrophil count was 41 times greater than that of the neonate, but at 24 h, neonatal peritoneal neutrophils had not yet reached the adult 4-h level. Peritoneal macrophages also increased more rapidly in adults than in neonates. After intraperitoneal infection, both adults and neonates developed bacteremia, but adults cleared the bacteria with greater efficiency. Adult blood neutrophils increased 247% by 12 h and then decreased; neonatal neutrophils steadily decreased to a 57% reduction by 24 h. These data suggest that the neonatal neutrophil response to group B streptococcus, type Ia, infection is inadequate and may contribute to the high mortality associated with this infection.