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Penicillin-intermediate pneumococci in a children's hospital
Abstract:
During the three-year period from 1981 to 1984, all clinical isolates of Streptococcus pneumoniae were screened for resistance to penicillin in the clinical bacteriology laboratory at The Children's Hospital of Alabama, Birmingham. Twenty-eight of 828 isolates were presumed resistant by disk diffusion testing with 1-microgram oxacillin disks (zone diameter, less than 20 mm). Seventeen of the 28 (61%) were found to be intermediately sensitive to penicillin by a conventional agar dilution method. Penicillin-intermediate strains had a minimal inhibitory concentration of 0.125 to 0.5 mg/L; no penicillin-resistant (minimal inhibitory concentration, greater than 1 mg/L) strains were encountered. The prevalence of penicillin-intermediate strains was thus 17 of 828 isolates, or 2.1%. These strains were also examined for susceptibility to ampicillin, vancomycin, cefotaxime, and chloramphenicol. We present the clinical features of 17 patients with disease due to penicillin-intermediate pneumococci.
Insights
Penicillin-intermediate Streptococcus pneumoniae strains were identified in 2.1% of clinical isolates. These findings highlight the emergence of antibiotic resistance in common bacterial pathogens.
Area of Science:
- Microbiology
- Infectious Diseases
- Clinical Bacteriology
Background:
- Antibiotic resistance in Streptococcus pneumoniae is a growing public health concern.
- Penicillin resistance has been observed in pneumococcal isolates globally.
- Surveillance of antimicrobial resistance is crucial for guiding treatment strategies.
Purpose of the Study:
- To determine the prevalence of penicillin-intermediate Streptococcus pneumoniae (S. pneumoniae) isolates.
- To characterize the antimicrobial susceptibility patterns of these intermediate strains.
- To describe the clinical features of patients infected with penicillin-intermediate S. pneumoniae.
Main Methods:
- Screening of all clinical S. pneumoniae isolates for penicillin resistance from 1981 to 1984.
- Disk diffusion testing with oxacillin disks to presume resistance.
- Conventional agar dilution method to determine minimal inhibitory concentrations (MICs) for penicillin.
- Susceptibility testing against ampicillin, vancomycin, cefotaxime, and chloramphenicol.
Main Results:
- Twenty-eight of 828 isolates were presumed resistant to penicillin by disk diffusion.
- Seventeen isolates (61% of presumed resistant) were confirmed as penicillin-intermediate (MIC 0.125-0.5 mg/L).
- No penicillin-resistant strains (MIC >1 mg/L) were detected; prevalence of intermediate strains was 2.1%.
Conclusions:
- Penicillin-intermediate S. pneumoniae strains were present in clinical isolates during the study period.
- These intermediate strains showed varying susceptibility to other antibiotics tested.
- Understanding the prevalence and characteristics of penicillin-intermediate pneumococci is important for patient management.