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Experimental infections for the evaluation of beta-lactamase resistance
Abstract:
The antibacterial activity and pharmacokinetics of the beta-lactamase-stable cephalosporin cefuroxime and the gram-negative beta-lactamase-susceptible cephalosporin cefazolin were compared in two contrasting infection models in which Proteus morganii 82, which produces chromosomally mediated beta-lactamase, was the pathogen. In the rat paw model, characterized by high numbers of localized bacteria, cefazolin was destroyed at the site of infection and consequently did not produce a therapeutic response. In the mouse intraperitoneal model cefazolin was also inactive, despite peritoneal concentrations being unaffected by high counts of the beta-lactamase-producing P. morganii in the body cavity. In contrast the pharmacokinetics of cefuroxime was unaffected by the presence of the beta-lactamase-producing P. morganii, and good therapeutic responses were seen in both models.
Insights
Cefuroxime demonstrated superior antibacterial activity against Proteus morganii compared to cefazolin. Cefuroxime maintained efficacy in infection models, while cefazolin was inactivated by beta-lactamase.
Area of Science:
- Pharmacology
- Microbiology
- Infectious Diseases
Background:
- Beta-lactamase production by bacteria poses a significant challenge to antibiotic efficacy.
- Proteus morganii is a Gram-negative bacterium known to produce beta-lactamase.
- Cephalosporins, such as cefazolin and cefuroxime, are crucial antibiotics for treating bacterial infections.
Purpose of the Study:
- To compare the antibacterial activity and pharmacokinetics of cefuroxime and cefazolin.
- To evaluate antibiotic performance in infection models involving a beta-lactamase-producing pathogen, Proteus morganii.
- To determine the impact of bacterial beta-lactamase on cephalosporin efficacy.
Main Methods:
- Comparative study of two cephalosporins: cefuroxime (beta-lactamase-stable) and cefazolin (beta-lactamase-susceptible).
- Infection models utilized: rat paw (localized infection) and mouse intraperitoneal (systemic infection).
- Pathogen employed: Proteus morganii 82, characterized by chromosomally mediated beta-lactamase production.
Main Results:
- Cefazolin was inactivated at the infection site in the rat paw model, resulting in no therapeutic response.
- Cefazolin also proved inactive in the mouse intraperitoneal model, despite unaffected peritoneal concentrations.
- Cefuroxime's pharmacokinetics were unaffected by beta-lactamase-producing Proteus morganii, with good therapeutic responses observed in both models.
Conclusions:
- Cefuroxime exhibits robust antibacterial activity and favorable pharmacokinetics in the presence of bacterial beta-lactamase.
- Cefazolin's efficacy is compromised by beta-lactamase production, rendering it ineffective in these experimental models.
- Beta-lactamase stability is a critical factor for cephalosporin effectiveness against susceptible pathogens like Proteus morganii.