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First report on a foodborne outbreak of Streptococcus dysgalactiae Subsp. equisimilis in China
Junhong Li1, Bowen Tu1, Xujian Mao1
1Changzhou Center for Disease Control and Prevention, Jiangsu, 213000, China.
Introduction:
Streptococcus dysgalactiae subsp. equisimilis (SDSE), a Gram-positive, beta-hemolytic group G Streptococcus, possesses virulence factors such as M protein, streptolysin O, streptolysin S, streptokinase, and hyaluronidase. This study reports a foodborne outbreak caused by SDSE infection recently occurred in China.
Methods:
In April 2019, an acute tonsillitis outbreak involving 155 patients occurred in a company in Changzhou, Jiangsu Province, China. Epidemiological surveys and laboratory investigations were conducted to identify the cause.
Results:
All patients were clinically diagnosed with acute suppurative tonsillitis or acute pharyngitis. SDSE was identified as the causative pathogen, isolated form 81.4% (35/43) of patients, 12.5% (1/8) of canteen staff, and 33.3% (1/3) of tested food samples (fried meat). Multilocus sequence typing (MLST) and emm typing confirmed all isolates as ST98-stG480.0, suggesting contamination of fried meat by an SDSE-carrying canteen staff member as the source of the outbreak. The mean onset time was 45.8 h, with an SDSE prevalence rate of 27.2%.
Conclusions:
This study is the first to report a foodborne outbreak caused by SDSE in Changzhou city since 2003. The identified strain, ST98-stG480.0, was exclusively associated with respiratory infections and exhibited no gastrointestinal symptoms. These findings underscore the importance of enhanced surveillance and in-depth investigation into the characteristics and public health implications of this strain.
Insights
A foodborne outbreak of Streptococcus dysgalactiae subsp. equisimilis (SDSE) caused acute tonsillitis in China. The outbreak strain ST98-stG480.0 was linked to contaminated fried meat and canteen staff.
Area of Science:
- Microbiology
- Infectious Diseases
- Public Health
Background:
- Streptococcus dysgalactiae subsp. equisimilis (SDSE) is a Gram-positive bacterium known for its virulence factors.
- SDSE infections can manifest in various ways, necessitating thorough investigation.
Purpose of the Study:
- To identify the causative agent of a foodborne outbreak of acute tonsillitis in Changzhou, China.
- To characterize the specific strain of SDSE involved and determine its source.
Main Methods:
- Epidemiological surveys and laboratory investigations were conducted during an outbreak involving 155 patients.
- Multilocus sequence typing (MLST) and emm typing were used to analyze isolated SDSE strains.
Main Results:
- SDSE was identified as the pathogen, isolated from 81.4% of patients, canteen staff, and food samples (fried meat).
- All isolates were confirmed as ST98-stG480.0, indicating food contamination via an infected canteen staff member.
- The outbreak involved acute suppurative tonsillitis/pharyngitis, with a mean onset time of 45.8 hours.
Conclusions:
- This is the first reported foodborne SDSE outbreak in Changzhou since 2003.
- The ST98-stG480.0 strain was linked to respiratory infections, not gastrointestinal symptoms.
- Enhanced surveillance and investigation of this SDSE strain's characteristics and public health impact are crucial.
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