Dexamethasone effects on group B streptococcal infection in newborn rats.
BACKGROUND
We previously published that human neutrophil-mediated bacterial killing of group B Streptococcus (GBS) in vitro was dependent on the timing and concentration of dexamethasone exposure.


OBJECTIVE
Dexamethasone treatment would affect neutrophil mediated killing of GBS in an animal model.


METHODS
Wistar rat pups were randomly allocated to receive placebo or dexamethasone before, early or late after GBS infection. Suckling rats were infected with 104 or 105 colony-forming units of GBS or nothing. Pups were followed for survival, quantitative bacteremia, growth and neutrophil-mediated bacterial killing. Neutrophils for bacterial killing were obtained via cardiac puncture before infection. Statistics included chi square for survival, Mann-Whitney U test for bacteremia, analysis of variance for growth and paired Student's t test for bacterial killing analyses.


RESULTS
Dexamethasone treatment before invasive GBS infection decreases quantitative bacteremia, improves survival and improves neonatal neutrophil-mediated bacterial killing in suckling rats, whereas dexamethasone treatment after infection increases bacteremia and decreases survival. Regardless of timing of dexamethasone treatment, before or after invasive GBS infection, growth was significantly impaired in all suckling rats receiving dexamethasone compared with controls.


CONCLUSIONS
Treatment with dexamethasone before invasive GBS infection improves survival and decreases bacteremia in suckling rats; this appears in part to be mediated by improved neonatal neutrophil-mediated bacterial killing. We speculate that this improvement in outcome may be a result of improved number or function of neutrophil cell surface receptors.
Tran
Thuy-Van P
TV
Section of Noenatology, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA.
Weisman
Leonard E
LE
D000818:Animals; D000831:Animals, Newborn; D016470:Bacteremia / Q000188:drug therapy*; D003907:Dexamethasone / Q000494:pharmacology*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D008297:Male; D011336:Probability; D011897:Random Allocation; D051381:Rats; D012016:Reference Values; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections / Q000188:drug therapy* / Q000401:mortality; D013292:Streptococcus agalactiae / Q000187:drug effects*; D015996:Survival Rate
D003907:Dexamethasone