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[Changes in the sensitivity of pneumococci to antibiotics. Therapeutic consequences]
1Centre National de Référence des Pneumocoques, GEEP, Service de Microbiologie, Centre Hospitalier Intercommunal, Créteil.
Abstract:
Streptococcus pneumoniae has a prominent role in infectious bronchopulmonary diseases. This organism is normally sensitive to a vast number of antibiotics. However, in recent years, acquired resistance against tetracyclines, macrolides, and, more recently, penicillins, has emerged. Since 1987, there is indeed a regular increase in the frequency of strains that have a lower sensitivity to penicillin G (less than 1% before 1986; 12% in 1990). However, this percentage of strains with a lower sensitivity is much more important among non-invasive as opposed to invasive organisms that are isolated from blood, pleural and spinal fluid cultures (3.3% in 1990). Among strains with abnormal sensitivity to penicillin G, there are very selective serotypes or serogroups: 4 types or groups (23, 19, 6 and 14) represent 80% of these strains. More than 80% of the strains of MIC greater than 2 mg/l are among only one stereotype, 23F. This abnormal sensitivity to penicillin G implies a modification of sensitivity to all beta-lactams, but MIC increase to a variable extent depending on the antiinfectious agent. The most efficient agents against strains of lower sensitivity are amoxicillin, imipenem and parenteral third generation cephalosporins. On the other hand, for all oral first, second and third generation cephalosporins, MIC increase to levels for which seric levels that are reached hardly demonstrate convincing efficiency. Even if resistance levels are less marked as shown by strains isolated from pulmonary infections as compared to what is seen in ENT, the trend in the development of abnormal sensitivity of pneumococci to beta-lactam agents urges the clinician to take into account these data in the therapeutic coverage of bronchopulmonary infections.
Insights
Streptococcus pneumoniae resistance to penicillin G is increasing, particularly in non-invasive strains. Clinicians must consider this emerging antibiotic resistance when treating bronchopulmonary infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Streptococcus pneumoniae is a major cause of bronchopulmonary infections.
- Antibiotic resistance, particularly to penicillin G, has emerged in S. pneumoniae.
- Resistance trends show a significant increase since 1987.
Purpose of the Study:
- To investigate the emerging resistance of Streptococcus pneumoniae to penicillin G.
- To identify specific serotypes associated with reduced penicillin sensitivity.
- To evaluate the impact of this resistance on the efficacy of various beta-lactam antibiotics.
Main Methods:
- Analysis of historical data on penicillin G sensitivity frequencies.
- Identification and characterization of S. pneumoniae serotypes.
- Determination of minimum inhibitory concentrations (MICs) for various beta-lactam agents against resistant strains.
Main Results:
- Penicillin G resistance in S. pneumoniae increased from <1% before 1986 to 12% in 1990.
- Non-invasive strains showed higher rates of reduced penicillin sensitivity (3.3% in 1990) compared to invasive strains.
- Serotypes 23, 19, 6, and 14 accounted for 80% of resistant strains, with serotype 23F being predominant.
- Reduced penicillin sensitivity correlated with cross-resistance to other beta-lactams, varying in extent.
- Amoxicillin, imipenem, and parenteral third-generation cephalosporins remained effective against less sensitive strains.
Conclusions:
- Emerging penicillin G resistance in S. pneumoniae poses a therapeutic challenge.
- Specific serotypes are disproportionately affected by this resistance.
- Clinicians must consider evolving antibiotic resistance patterns when managing bronchopulmonary infections.