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Penicillin tolerance in beta-streptococci isolated from patients with tonsillitis
Abstract:
Beta-streptococci isolated from patients with acute tonsillitis were tested for penicillin tolerance defined as an MBC/MIC ratio greater than or equal to 16. 11/18 strains recovered from patients with clinical treatment failure were tolerant to penicillin in comparison with 0/15 strains from successfully treated patients. The MBC/MIC ratio was less than 16 for all strains versus cefadroxil but above that ratio for many strains versus clindamycin, doxycycline and erythromycin. We suggest that penicillin tolerance may be one reason to treatment failures in individuals with streptococcal tonsillitis and that other antibiotics could be used to treat these patients since penicillin tolerance is not correlated to a general increase in antibiotic resistance.
Insights
Penicillin tolerance in beta-streptococci may explain treatment failures in acute tonsillitis. This tolerance was not linked to general antibiotic resistance, suggesting alternative antibiotics may be more effective for patients experiencing treatment failure.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Acute tonsillitis is commonly caused by beta-hemolytic streptococci.
- Penicillin is a standard treatment, but treatment failures occur.
- Antibiotic tolerance, defined by a high Minimum Bactericidal Concentration (MBC)/Minimum Inhibitory Concentration (MIC) ratio, is a potential mechanism for treatment failure.
Purpose of the Study:
- To investigate the prevalence of penicillin tolerance in beta-streptococci isolated from patients with acute tonsillitis.
- To determine if penicillin tolerance correlates with clinical treatment outcomes.
- To assess tolerance to other antibiotics (cefadroxil, clindamycin, doxycycline, erythromycin) in these strains.
Main Methods:
- Beta-streptococci were isolated from patients with acute tonsillitis.
- Penicillin tolerance was assessed using the MBC/MIC ratio (≥16).
- Strains were categorized based on clinical treatment success or failure.
- Tolerance to cefadroxil, clindamycin, doxycycline, and erythromycin was also evaluated.
Main Results:
- Eleven of 18 strains (61%) from patients with treatment failure exhibited penicillin tolerance.
- No strains (0/15) from successfully treated patients showed penicillin tolerance.
- All strains were susceptible to cefadroxil (MBC/MIC < 16).
- Many strains demonstrated tolerance to clindamycin, doxycycline, and erythromycin.
Conclusions:
- Penicillin tolerance in beta-streptococci may be a significant factor contributing to treatment failures in acute tonsillitis.
- Penicillin tolerance does not appear to be associated with broader antibiotic resistance.
- Alternative antibiotics like cefadroxil, clindamycin, doxycycline, or erythromycin may be considered for patients with persistent streptococcal tonsillitis, especially if penicillin tolerance is suspected.