Molecular analysis of Streptococcus pyogenes strains isolated from patients with recurrent pharyngitis after oral amoxicillin treatment

J Med Microbiol. 2018 Nov;67(11):1544-1550. doi: 10.1099/jmm.0.000833. Epub 2018 Sep 24.

Abstract

Purpose: The most common illness caused by Streptococcus pyogenes (Group A streptococcus; GAS) is acute pharyngitis. It has been reported that a small percentage of patients experience recurrent GAS pharyngitis after 10 days of treatment with oral amoxicillin. The aim of this study was to clarify whether recurrent GAS pharyngitis is reactivation caused by the primary strain remaining at the infection site, or if the reinfection is caused by newly acquired strains.

Methodology: A total of 135 GAS clinical strains were isolated from the tonsils of 116 pediatric patients with acute GAS pharyngitis between November, 2012 and April, 2014 in Saga, Japan. These strains were analysed by pulsed-field gel electrophoresis (PFGE)-typing methods.

Results: The isolates were grouped into 16 PFGE-types. The epidemic PFGE types that caused pharyngitis were found to change dynamically during 18 months. Eleven strains caused recurrent pharyngitis within 40 days after the last treatment, all of them showing the same PFGE-type as the primary strains. Eight of the strains caused recurrence more than 40 days after the treatment. Among them, six showed different PFGE-types from the primary strains.

Conclusion: When recurrent pharyngitis emerges more than 40 days after the last treatment, penicillin can be prescribed again because reinfection is suspected. However, when recurrent pharyngitis takes place within 40 days after completing the treatment, alternative drugs should be considered for retreatment because the pharyngitis is likely to be due to reactivation.

Keywords: Group A streptococcus; PFGE typing; Streptococcus pyogenes; emm typing; recurrent pharyngitis.

MeSH terms

  • Administration, Oral
  • Amoxicillin / administration & dosage*
  • Amoxicillin / pharmacology
  • Amoxicillin / therapeutic use
  • Anti-Bacterial Agents / administration & dosage*
  • Anti-Bacterial Agents / pharmacology
  • Anti-Bacterial Agents / therapeutic use
  • Antigens, Bacterial / genetics
  • Bacterial Outer Membrane Proteins / genetics
  • Carrier Proteins / genetics
  • Child
  • Child, Preschool
  • Electrophoresis, Gel, Pulsed-Field
  • Female
  • Genotype
  • Humans
  • Japan / epidemiology
  • Male
  • Microbial Sensitivity Tests
  • Molecular Typing
  • Pharyngitis / drug therapy*
  • Pharyngitis / epidemiology
  • Pharyngitis / microbiology
  • Recurrence
  • Streptococcal Infections / drug therapy*
  • Streptococcal Infections / epidemiology
  • Streptococcal Infections / microbiology
  • Streptococcus pyogenes / classification
  • Streptococcus pyogenes / drug effects*
  • Streptococcus pyogenes / genetics*
  • Streptococcus pyogenes / isolation & purification

Substances

  • Anti-Bacterial Agents
  • Antigens, Bacterial
  • Bacterial Outer Membrane Proteins
  • Carrier Proteins
  • streptococcal M protein
  • Amoxicillin