Lethal Haemophilus influenzae type b infection in mice.

Previous animal models of invasive Haemophilus influenzae type b (HITB) infection are characterized by a low mortality rate. We produced a highly lethal infection in CF1 mice using mouse passage, mucin, and hemoglobin to enhance infectivity. Infection by the intraperitoneal route was followed by progressive peritonitis and bacteremia with subsequent HITB infection of the brain and meninges, and death. Death occurred between eight and 72 hours after infection and was associated with 10(6) to 10(9) HITB per ml of blood and with 10(2) to 10(5) HITB per g of brain. Mucin-hemoglobin did not augment HITB growth, but impaired macrophage adherence to glass in vitro, without decreasing cellular viability. In vivo, mucin-hemoglobin decreased the rate of disappearance of 51Cr-labelled HITB from the blood by impairment of hepatic clearance. This technically simple and inexpensive model is useful for the study of HITB infections in which bacterial multiplication, invasion and host lethality are desired features.