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Antibiotic resistance and penicillin tolerance in clinical isolates of group B streptococci
1Servicio de Microbiología Clínica, Hospital Universitario San Carlos, Madrid, Spain.
Abstract:
The aim of this study was to determine the susceptibility patterns of 100 group B streptococcal strains isolated in our hospital and to ascertain tolerance to penicillin by determining quantitative killing curves. We found two strains with intermediate susceptibility to penicillin and eight strains to ampicillin. Seventeen isolates were tolerant to penicillin, with bacterial counts decreasing 2 to 3 log during the first 8 h but still above 10(2) CFU/ml after 24 h. The kinetic study shows that penicillin tolerance is not rare among group B streptococci isolated in our hospital.
Insights
Penicillin tolerance is common in hospital-acquired group B streptococci (GBS). This study found 17% of GBS strains exhibited penicillin tolerance, suggesting potential treatment challenges.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Group B Streptococcus (GBS) is a significant cause of neonatal infections.
- Penicillin is the recommended treatment for GBS infections.
- Understanding antimicrobial susceptibility and tolerance is crucial for effective treatment.
Purpose of the Study:
- To determine the penicillin susceptibility patterns of 100 clinical isolates of group B Streptococcus.
- To assess the tolerance of GBS strains to penicillin using quantitative killing curves.
Main Methods:
- Isolation and identification of 100 group B streptococcal strains from clinical samples.
- Determination of minimum inhibitory concentrations (MICs) for penicillin and ampicillin.
- Quantitative killing curve assays to assess bacterial killing kinetics over 24 hours.
Main Results:
- Two strains showed intermediate susceptibility to penicillin, and eight strains to ampicillin.
- Seventeen isolates (17%) were found to be tolerant to penicillin.
- Penicillin-tolerant strains showed a 2-3 log decrease in bacterial count within 8 hours, but remained above 10^2 CFU/ml after 24 hours.
Conclusions:
- Penicillin tolerance is a notable phenomenon among group B streptococci isolated in this hospital.
- The prevalence of penicillin tolerance suggests potential challenges in eradicating GBS infections with penicillin therapy.
- Further research into the mechanisms and clinical implications of GBS penicillin tolerance is warranted.