Bortolussi R, Burbridge S, Durnford P, Schellekens H
Department of Pediatrics, Dalhousie University, Halifax, Canada.
Pediatr Res. 1991 Apr;29(4 Pt 1):400-2. doi: 10.1203/00006450-199104000-00014.
Despite aggressive treatment, early onset neonatal Listeria monocytogenes infection continues to have high morbidity and mortality. We recently showed that pretreatment of newborn L. monocytogenes-infected rats with interferon (IFN)-alpha/beta or recombinant rat IFN-gamma dramatically improves survival. However, in the present experiment, when newborn rats were treated with IFN-alpha/beta or recombinant rat IFN-gamma after intraperitoneal injection with Listeria there was no benefit. Because most deaths occurred at or before 3 d in this animal model, we reasoned that the effect of interferon may be evident if animals survived longer. To accomplish this and test this hypothesis, ampicillin (20 mg/kg/d) was given 48 h after bacterial challenge. When ampicillin-treated Listeria-infected rats were randomized to receive PBS, IFN-alpha/beta, or recombinant rat IFN-gamma, mortality rates were 79, 76, and 69%, respectively (p greater than 0.05 versus PBS). Animals treated in a similar fashion after a lower bacterial inoculum (25% lethal dose) were killed 5 d after bacterial challenge. Bacterial concentrations in the spleen were higher for IFN-treated animals than controls. We conclude that no direct benefit of IFN is found if it is given after bacterial infection has been established.
