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Evaluation of ceftazidime, ampicillin and chloramphenicol in experimental Haemophilus influenzae type b meningitis
Abstract:
In an infant rat model of Haemophilus influenzae, type b meningitis, where treatment was given 24 and 48 h after infection, the dose of ceftazidime required to eradicate the infection from the CSF of half the animals (CD50) ranged from less than 0.15-1.5 mg/kg/dose. The accompanying blood infections were marginally less responsive to therapy with CD50 values ranging from 0.5-3.9 mg/kg/dose. Comparable data for ampicillin were 12.5-40 mg/kg/dose and 20- greater than 200 mg/kg/dose for the CSF and blood infections while those for chloramphenicol were 18- greater than 100 mg/kg/dose and 22- greater than 100 mg/kg/dose for the CSF and blood infections respectively. Investigation of the relative rates of kill in vivo showed that all three drugs rapidly reduced the bacterial numbers to minimal levels. However, whereas ceftazidime completely eradicated the infection, chloramphenicol, and to a lesser extent, ampicillin-treated rats experienced substantial relapsing. Ceftazidime penetrated into the CSF of infected and uninfected rats slightly better than ampicillin--7.3% compared to 4.0% of the corresponding blood levels respectively. These results indicate that ceftazidime is significantly more active in the infant rat model of H. influenzae, type b meningitis than ampicillin or chloramphenicol.
Insights
Ceftazidime effectively eradicates Haemophilus influenzae type b meningitis in infant rats, outperforming ampicillin and chloramphenicol. This study highlights ceftazidime
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- Haemophilus influenzae type b (Hib) meningitis remains a significant threat, particularly in infants.
- Evaluating antibiotic efficacy against Hib meningitis is crucial for treatment strategies.
Purpose of the Study:
- To compare the efficacy of ceftazidime, ampicillin, and chloramphenicol in an infant rat model of Hib meningitis.
- To assess antibiotic penetration into cerebrospinal fluid (CSF) and eradication rates.
Main Methods:
- An infant rat model of Hib meningitis was utilized.
- Antibiotic doses (ceftazidime, ampicillin, chloramphenicol) were administered 24 and 48 hours post-infection.
- Cerebrospinal fluid (CSF) and blood infections were evaluated for bacterial eradication.
- In vivo bacterial kill rates and drug penetration into CSF were measured.
Main Results:
- Ceftazidime demonstrated superior efficacy, eradicating infection at significantly lower doses (CD50 <0.15-1.5 mg/kg) compared to ampicillin (12.5-40 mg/kg) and chloramphenicol (18->100 mg/kg).
- While all drugs initially reduced bacterial load, ceftazidime achieved complete eradication, whereas ampicillin and chloramphenicol showed substantial relapse rates.
- Ceftazidime exhibited better penetration into the CSF (7.3% of blood levels) compared to ampicillin (4.0%).
Conclusions:
- Ceftazidime is significantly more effective than ampicillin and chloramphenicol for treating Hib meningitis in this infant rat model.
- Superior CSF penetration and complete eradication underscore ceftazidime's potential as a primary therapeutic agent for Hib meningitis.
- Relapse rates observed with ampicillin and chloramphenicol suggest limitations in their use for this condition.