Erythromycin resistance in Streptococcus pyogenes in Italy

Area of Science:

• Pediatric infectious diseases
• Microbiology
• Pharmacology

Background:

• Acute pharyngitis is a common childhood illness.
• Streptococcus pyogenes is a primary bacterial cause of acute pharyngitis.
• Antibiotic resistance, particularly to macrolides, is a growing concern.

Purpose of the Study:

• To investigate the prevalence of macrolide resistance in Streptococcus pyogenes causing acute pharyngitis in Italian children.
• To evaluate the clinical effectiveness of clarithromycin in treating S. pyogenes infections based on macrolide susceptibility.
• To identify factors associated with treatment failure.

Main Methods:

• Prospective study design.
• Isolates of Streptococcus pyogenes collected from children with acute pharyngitis.
• Macrolide susceptibility testing performed on bacterial isolates.
• Clinical outcomes assessed following clarithromycin treatment.

Main Results:

• 38.3% of 180 Streptococcus pyogenes isolates were resistant to macrolides.
• Clarithromycin eradicated S. pyogenes in 63.1% of patients with erythromycin-resistant strains (n=19).
• Eradication rates were higher (88%) in patients with erythromycin-susceptible strains (n=25).
• Constitutive macrolide resistance phenotype correlated with treatment failure.

Conclusions:

• Macrolide resistance in Streptococcus pyogenes is prevalent in Italian children with acute pharyngitis.
• Clarithromycin effectiveness is significantly reduced in the presence of erythromycin-resistant S. pyogenes.
• The constitutive-resistant phenotype is a predictor of macrolide treatment failure in pediatric pharyngitis.