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Efficacy of beta-lactams against experimental pneumococcal endocarditis caused by strains with different

Cristina Pichardo1, Fernando Docobo-Pérez, Maria E Pachón-Ibáñez

  • 1Infectious Diseases Service, Virgen del Rocío University Hospitals, Sevilla, Spain. cristina.pichardo.exts@juntadeandalucia.es

The Journal of Antimicrobial Chemotherapy
|September 10, 2005
PubMed
Abstract

Insights

Penicillin remains effective against Streptococcus pneumoniae infections, even with resistant strains. This study suggests current susceptibility breakpoints for penicillin may need reevaluation.

Area of Science:

  • Microbiology and Infectious Diseases
  • Pharmacology and Therapeutics

Background:

  • Streptococcus pneumoniae is a significant cause of bacterial infections.
  • Antimicrobial resistance in S. pneumoniae necessitates ongoing evaluation of treatment efficacy.
  • Understanding the in vitro and in vivo activity of antibiotics is crucial for clinical decision-making.

Purpose of the Study:

  • To compare the in vitro and in vivo activity of penicillin, cefotaxime, and ceftriaxone against Streptococcus pneumoniae.
  • To assess antibiotic efficacy using strains with varying penicillin minimum inhibitory concentrations (MICs).

Main Methods:

  • In vitro time-kill curves were performed.
  • An experimental rabbit model of endocarditis was utilized.
  • Three S. pneumoniae strains with penicillin MICs of 0.015, 0.25, and 2 mg/L were tested.

Main Results:

  • Penicillin demonstrated significant efficacy in clearing bacteria from vegetations and blood, regardless of penicillin susceptibility (P < 0.01 vs. controls).
  • Cefotaxime and ceftriaxone exhibited similar efficacy to penicillin in the in vivo model.
  • Penicillin showed superior results in the in vivo endocarditis model compared to in vitro time-kill curves.

Conclusions:

  • Penicillin is efficacious for treating pneumococcal infections, including those caused by strains with MICs up to 2 mg/L (excluding meningitis).
  • Current breakpoints for defining S. pneumoniae susceptibility and resistance to penicillin warrant review.
  • Reevaluation of breakpoints is suggested, similar to recent changes for amoxicillin and third-generation cephalosporins.

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