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Characterization of Streptococcus pyogenes Strains from Tonsillopharyngitis and Scarlet Fever Resurgence, 2023-FIRST
Emma Keuleyan1, Theodor Todorov2,3, Deyan Donchev4
1Clinical Microbiology and Virology Laboratory, University Hospital "Lozenetz", 1407 Sofia, Bulgaria.
Abstract:
Recently a resurgence of Streptococcus pyogenes infections has arisen, with concerns around the highly virulent M1UK lineage. Our aim was to characterize S. pyogenes, the immune responses it causes, and to determine the presence of the M1UK lineage in Sofia, Bulgaria. In our study, the infections were confirmed by culture testing or rapid antigen test. Identification was performed by MALDI-TOF and was followed up by antibiotic susceptibility testing (EUCAST). Virulence factors were identified using multiplex PCR and whole genome sequencing (WGS). Immune responses were measured through detection of serum complement levels, lymphocyte subsets, and cytokine profiling. Out of 82 children, 38 had scarlet fever and the rest had streptococcal pharyngitis. Strains were susceptible to penicillin (β-lactams), macrolides, clindamycin, tetracyclines, co-trimoxazole, fluoroquinolones, and linezolid. Superantigen profiles were identified: SpeA + SpeJ (45%), SpeC, and SpeI + SpeH (27.5% each). A novel Multilocus sequence typing (MLST) haplotype in the mutS gene (d90b) was found in four strains. The M1UK lineage was detected for the first time in Bulgaria. We observed an increase in complement fractions C3 and C4 and a decrease in T lymphocytes. A significant increase in the levels of IFN-γ, IL-6, and IL-10 with corresponding reduction in IL-17A were revealed. In conclusion, the studied S. pyogenes strains were characterized by their susceptibility to antibiotics and the predominance of SpeA superantigen; for the first time in Bulgaria the presence of M1UK and a novel SNP variation in the mutS gene (d90b) were found. A mixed pattern of pro- and anti-inflammatory immune responses in patients was observed.
Insights
A study in Bulgaria identified the virulent M1UK lineage of Streptococcus pyogenes, finding strains susceptible to antibiotics and a mixed immune response in scarlet fever patients. This marks the first detection of M1UK in Bulgaria.
Area of Science:
- Microbiology
- Immunology
- Infectious Diseases
Background:
- Resurgence of virulent *Streptococcus pyogenes* infections, particularly the M1UK lineage, necessitates characterization.
- Understanding the immune response to *S. pyogenes* is crucial for managing infections like scarlet fever and streptococcal pharyngitis.
- Limited data exists on the prevalence of specific *S. pyogenes* lineages and their associated virulence factors in Bulgaria.
Purpose of the Study:
- To characterize *Streptococcus pyogenes* strains isolated from children in Sofia, Bulgaria.
- To investigate the immune responses induced by these *S. pyogenes* infections.
- To determine the presence and characteristics of the M1UK lineage in Bulgaria.
Main Methods:
- Bacterial identification using MALDI-TOF and antibiotic susceptibility testing (EUCAST).
- Virulence factor analysis via multiplex PCR and whole genome sequencing (WGS).
- Immune response assessment through serum complement levels, lymphocyte subsets, and cytokine profiling.
Main Results:
- Identified *S. pyogenes* in 82 children (38 with scarlet fever); all strains were susceptible to common antibiotics.
- Predominant superantigen profiles included SpeA + SpeJ (45%); detected a novel MLST haplotype (d90b) in the *mut*S gene.
- Confirmed the presence of the M1UK lineage in Bulgaria for the first time, alongside observed increases in C3/C4, IFN-γ, IL-6, IL-10, and decreases in T lymphocytes and IL-17A.
Conclusions:
- The *S. pyogenes* strains studied in Bulgaria are antibiotic-susceptible with a predominant SpeA superantigen.
- The M1UK lineage and a novel *mut*S gene SNP variation (d90b) were identified in Bulgaria.
- Observed a complex immune response pattern with both pro- and anti-inflammatory markers in infected patients.
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Acute pharyngitis is the inflammation of the back of the throat (pharynx), commonly resulting in a sore throat. It is a frequently encountered condition that prompts individuals to seek medical advice.
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Acute pharyngitis can be categorized based on its underlying cause: