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Streptococcus pneumoniae in community-acquired pneumonia. How important is drug resistance?
1Department of Respiratory and Critical Care Medicine, Medizinische Universitätsklinik und Poliklinik II Bonn, Bonn, Germany.
Abstract:
Patients hospitalized with community-acquired pneumonia caused by S. pneumoniae strains with intermediate susceptibility to penicillin according to the conventional definition respond well to treatment with adequate doses of beta-lactam antibiotics. All studies currently available comparing mortality between patients with pneumonia caused by nonsusceptible and susceptible pneumococci agree that resistance of MIC 2 mg/L is not associated independently with an increased mortality. Most but not all studies could not prove an effect of microbial resistance on morbidity. There are data suggesting, however, that pneumococcal pneumonia caused by highly resistant strains (MIC > or = 4 mg/L) does affect the outcome. Pneumococcal resistance remains a matter of concern. Most reports show an increase not only of resistance rates, but also of the proportion of highly resistant strains. The selection of initial empirical antimicrobial treatment of patients with community-acquired pneumonia should be performed judiciously. Because the serum and pulmonary levels achieved with penicillin or related drugs are several times higher than the MICs of most strains, pneumonias caused by S. pneumoniae currently defined as not susceptible to penicillin should respond well to treatment with a beta-lactam antibiotic, used in optimal doses. Consequently, there is no reason fundamentally to change the current approach to initial empiric antimicrobial treatment of patients with community-acquired pneumonia. Nevertheless, increases in resistance to macrolides may prompt a limited use of these drugs in the outpatient setting. In any case, treatment failures may occur at higher levels of resistance, and a change in the definition of susceptibility categories toward higher cutoffs for S. pneumoniae seems to be reasonable.
Insights
Patients with community-acquired pneumonia caused by penicillin-intermediate Streptococcus pneumoniae respond well to beta-lactam antibiotics. While high-level resistance may impact outcomes, current treatment approaches for pneumonia remain effective.
Area of Science:
- Infectious Diseases
- Microbiology
- Pharmacology
Background:
- Community-acquired pneumonia (CAP) is a significant global health concern.
- Streptococcus pneumoniae is a primary causative agent of CAP.
- Antimicrobial resistance in S. pneumoniae necessitates ongoing evaluation of treatment guidelines.
Purpose of the Study:
- To assess the impact of penicillin-intermediate and resistant Streptococcus pneumoniae strains on patient outcomes in community-acquired pneumonia.
- To evaluate the efficacy of current beta-lactam antibiotic treatment strategies against S. pneumoniae with varying levels of penicillin susceptibility.
- To inform antimicrobial stewardship and treatment guidelines for CAP.
Main Methods:
- Review and synthesis of existing studies comparing mortality and morbidity in patients with CAP caused by susceptible, intermediate, and resistant S. pneumoniae strains.
- Analysis of minimum inhibitory concentration (MIC) data in relation to treatment outcomes.
- Evaluation of pharmacokinetic/pharmacodynamic (PK/PD) principles for beta-lactam antibiotics against S. pneumoniae.
Main Results:
- Patients with S. pneumoniae strains intermediate to penicillin respond well to adequate doses of beta-lactam antibiotics.
- Penicillin resistance with MIC ≤ 2 mg/L is not independently associated with increased mortality.
- Pneumonia caused by highly resistant strains (MIC ≥ 4 mg/L) may negatively affect patient outcomes.
- Macrolide resistance is increasing, potentially limiting their use in outpatient settings.
Conclusions:
- Current treatment strategies for CAP caused by penicillin-intermediate S. pneumoniae remain appropriate.
- Judicious selection of empirical antimicrobial treatment is crucial.
- Consideration should be given to revising susceptibility category cutoffs for S. pneumoniae due to increasing resistance.
- While beta-lactams remain effective, vigilance regarding resistance trends is necessary.