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Experimental pneumonia due to Haemophilus influenzae: observations on pathogenesis and treatment
Abstract:
A model of pneumonia due to Haemophilus influenzae type b was developed in mice and used for exploration of the pathophysiology of the infection and evaluation of the efficacy of five antimicrobial agents. Adult C57BL/6 mice were challenged with 3 X 10(9) cfu of H influenzae by intratracheal inoculation. Mice given placebo or no treatment experienced a uniformly bacteremic and fatal infection. Animals given ampicillin, cefamandole, chloramphenicol, erythromycin plus sulfisoxazole, or fludalanine plus pentizidone (MK 0641/MK 0642, an investigational combination drug) survived at a higher rate than did controls (P less than .001 at 72 hr for each antibiotic). However, survival rates for the various antibiotic-treated groups were similar. Viable organisms were eradicated from the lungs of antibiotic-treated mice more quickly than from the lungs of controls (P less than .001 at 24 hr for each drug). Studies of pulmonary clearance revealed significant differences among regimens; the order of efficacy (from most to least) was ampicillin, chloramphenicol, erythromycin/sulfisoxazole, cefamandole, and fludalanine / pentizidone . This model represents an appropriate system for evaluation of invasive pulmonary infection caused by H influenzae type b. Of the antibiotics assessed, ampicillin was most active in vivo.
Insights
A new mouse model for Haemophilus influenzae type b pneumonia effectively evaluated antimicrobial treatments. Ampicillin demonstrated the highest efficacy in clearing the infection and improving survival rates in this model.
Area of Science:
- Infectious Diseases
- Microbiology
- Pharmacology
Background:
- Haemophilus influenzae type b (Hib) is a significant cause of bacterial pneumonia.
- Understanding Hib pathophysiology and evaluating effective treatments requires robust models.
- Previous models may not fully capture the invasive nature of Hib pulmonary infections.
Purpose of the Study:
- To develop and validate a mouse model for Haemophilus influenzae type b pneumonia.
- To investigate the pathophysiology of Hib-induced pneumonia.
- To evaluate the in vivo efficacy of five different antimicrobial agents against Hib.
Main Methods:
- Adult C57BL/6 mice were intratracheally inoculated with 3 x 10^9 cfu of H. influenzae.
- Infection severity, bacteremia, and survival rates were monitored in placebo and treated groups.
- Five antimicrobial agents were tested: ampicillin, cefamandole, chloramphenicol, erythromycin/sulfisoxazole, and fludalanine/pentizidone.
Main Results:
- All tested antimicrobial agents significantly improved survival rates compared to controls (P < .001 at 72 hr).
- Bacterial clearance from the lungs was significantly faster in all antibiotic-treated groups (P < .001 at 24 hr).
- Efficacy in pulmonary clearance varied, with ampicillin showing the greatest activity, followed by chloramphenicol, erythromycin/sulfisoxazole, cefamandole, and fludalanine/pentizidone.
Conclusions:
- The developed mouse model is suitable for studying invasive H. influenzae type b pulmonary infections.
- All evaluated antibiotics provided significant therapeutic benefits.
- Ampicillin exhibited the most potent in vivo activity against H. influenzae type b pneumonia in this model.