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Lethal Haemophilus influenzae type b infection in mice
Abstract:
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.
Insights
Researchers developed a lethal animal model for invasive Haemophilus influenzae type b (HITB) infection. This new model enhances bacterial infectivity and host lethality, aiding HITB research.
Area of Science:
- Microbiology
- Immunology
- Pathogenesis
Background:
- Existing animal models for invasive Haemophilus influenzae type b (HITB) infection exhibit low mortality rates.
- Developing a lethal model is crucial for studying HITB pathogenesis and evaluating interventions.
Purpose of the Study:
- To create a highly lethal and reproducible animal model for invasive Haemophilus influenzae type b (HITB) infection.
- To investigate the mechanisms by which mucin and hemoglobin enhance HITB infectivity and lethality.
Main Methods:
- CF1 mice were infected intraperitoneally with HITB, enhanced by mouse passage, mucin, and hemoglobin.
- Bacterial load in blood and brain, mortality rates, and survival times were assessed.
- In vitro macrophage adherence and in vivo hepatic clearance of HITB were evaluated.
Main Results:
- The model achieved high lethality, with death occurring 8–72 hours post-infection.
- Significant bacteremia (10^6–10^9 HITB/ml) and brain infection (10^2–10^5 HITB/g) were observed.
- Mucin-hemoglobin impaired macrophage adherence in vitro and reduced hepatic clearance in vivo, contributing to increased lethality.
Conclusions:
- A technically simple, inexpensive, and highly lethal HITB mouse model was established.
- This model facilitates the study of bacterial multiplication, invasion, and host lethality in HITB infections.
- The findings highlight the role of mucin-hemoglobin in enhancing HITB virulence through immune evasion and impaired clearance.