Penicillin-intermediate pneumococci in a children's hospital

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.