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Sensitivity to penicillin of S. pneumoniae strains isolated from various pathological conditions
Abstract:
297 S. pneumoniae strains isolated from patients with different pneumococcal infections during 1990-1991 were tested for the sensitivity to antibiotics--by the diffusimetric method to 9 antibiotics (Penicillin (6 micrograms), Ampicillin (10 micrograms), Erythromycin (15 micrograms), Oxacyllin (5 micrograms), Streptomycin (50 micrograms), Tetracycline (50 micrograms), Chloramphenicol (50 micrograms), Rifampicin (6 micrograms), and Kanamycin (30 micrograms) and by MIC determination to Penicillin and Erythromycin. 30% of S. pneumoniae strains were resistant to Penicillin and Erythromycin corresponding to a MIC > or = 1 UP/ml or > or = 1 microgram E/ml. The most active antibiotics were Chloramphenicol and Rifampicin and the less active: Tetracycline, Kanamycin and Streptomycin. A relation between the origin and serotype of the strains and the sensitivity to antibiotics was revealed. The strains from the throat, conjunctive and otic secretions and belonging to serotypes 19, 6 and 14 showed the highest levels of resistance to all antibiotics. A good correlation between MIC and diffusion method results was observed to Erythromycin and no correlation to Penicillin. In this last case the results of MIC determination to Penicillin were better correlated with the results of inhibitions diameters to Oxacyllin, method which have to be recommended.
Insights
This study found that 30% of Streptococcus pneumoniae strains were resistant to penicillin and erythromycin. Chloramphenicol and rifampicin showed the most activity against these common respiratory pathogens.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Streptococcus pneumoniae is a leading cause of bacterial infections, including pneumonia, meningitis, and otitis media.
- Antibiotic resistance in S. pneumoniae is a growing public health concern, necessitating ongoing surveillance of antimicrobial susceptibility patterns.
Purpose of the Study:
- To assess the antibiotic sensitivity of 297 S. pneumoniae strains isolated from various pneumococcal infections.
- To evaluate the correlation between different antibiotic susceptibility testing methods for S. pneumoniae.
Main Methods:
- Disk diffusion method was used to test sensitivity to 9 antibiotics: Penicillin, Ampicillin, Erythromycin, Oxacillin, Streptomycin, Tetracycline, Chloramphenicol, Rifampicin, and Kanamycin.
- Minimum Inhibitory Concentration (MIC) determination was performed for Penicillin and Erythromycin.
- Correlation analysis was conducted between MIC and disk diffusion results.
Main Results:
- 30% of S. pneumoniae strains exhibited resistance to Penicillin and Erythromycin (MIC ≥ 1 µg/ml).
- Chloramphenicol and Rifampicin were the most effective antibiotics, while Tetracycline, Kanamycin, and Streptomycin were less active.
- A correlation was observed between infection source (throat, conjunctiva, ear secretions) and serotype (19, 6, 14) with antibiotic resistance.
- Good correlation between MIC and disk diffusion was found for Erythromycin, but not for Penicillin. Oxacillin disk diffusion results correlated better with Penicillin MIC.
Conclusions:
- Significant rates of penicillin and erythromycin resistance in S. pneumoniae were identified.
- Antibiotic susceptibility varies by strain origin and serotype, highlighting the need for targeted treatment strategies.
- Oxacillin disk diffusion is recommended as a reliable method for predicting penicillin susceptibility in S. pneumoniae.