Characterisation of the main clones of Streptococcus pyogenes carrying the ermA (subclass TR) gene in Spain

Area of Science:

• Microbiology
• Molecular Biology
• Epidemiology

Background:

• Streptococcus pyogenes, a significant human pathogen, can develop resistance to antibiotics.
• Macrolide-lincosamide-streptogramin B (MLS(B)) resistance is a growing concern in S. pyogenes infections.
• The ermA gene is a common mechanism for MLS(B) resistance in S. pyogenes.

Purpose of the Study:

• To characterize the genetic diversity and antibiotic resistance profiles of Streptococcus pyogenes isolates exhibiting MLS(B) resistance.
• To investigate the prevalence of specific emm types and sequence types (STs) associated with the ermA gene.
• To determine the correlation between emm/ST types and resistance to other antibiotics, such as tetracycline.

Main Methods:

• Phenotypic detection of MLS(B) resistance and ermA gene presence.
• Molecular typing using emm gene sequencing and multilocus sequence typing (MLST) to determine sequence types (STs).
• Pulsed-field gel electrophoresis (PFGE) for genetic relatedness analysis.
• Tetracycline susceptibility testing and T-typing for serological characterization.

Main Results:

• Seventy-four S. pyogenes isolates with the MLS(B) resistance phenotype carrying ermA were analyzed.
• Seven distinct emm/ST types were identified, with emm22/ST46 and emm77/ST63 being the most prevalent.
• Tetracycline resistance was observed in all ST63 (tetO+) and ST89 (tetM+) isolates, while ST46 isolates were susceptible.
• PFGE revealed eight distinct pulsotypes, generally correlating with emm/ST types.

Conclusions:

• The study highlights the genetic diversity of MLS(B)-resistant S. pyogenes strains.
• Specific emm/ST types are associated with distinct resistance patterns, including tetracycline resistance.
• Understanding these molecular characteristics is crucial for effective treatment and control of S. pyogenes infections.