First human case report of sepsis due to infection with Streptococcus suis serotype 31 in Thailand
Rujirat Hatrongjit1, Anusak Kerdsin2,3, Marcelo Gottschalk4
1Faculty of Science and Engineering, Kasetsart University Chalermphrakiat Sakon Nakhon Province Campus, Muang, Sakon Nakhon Province, 47000, Thailand. h_rujirat@hotmail.com.
Background:
Streptococcus suis is a zoonotic pathogen that causes invasive infections in humans and pigs. It has been reported that S. suis infection in humans is mostly caused by serotype 2. However, human cases caused by other serotypes have rarely been reported. This is the first report of a human case of infection with S. suis serotype 31 in Thailand.
Case Presentation:
A 55-year-old male alcohol misuser with liver cirrhosis was admitted with sepsis to a hospital in the Central Region of Thailand. He had consumed a homemade, raw pork product prior to the onset of illness. He was alive after treatment with ceftriaxone and no complication occurred. An isolate from blood culture at the hospital was suspected as viridans group Streptococcus. It was confirmed at a reference laboratory as S. suis serotype 31 by biochemical tests, 16S rDNA sequencing, and multiplex polymerase chain reaction for serotyping, but it was untypable by the co-agglutination test with antisera against recognized S. suis serotypes, suggesting loss of capsular material. The absence of a capsule was confirmed by transmission electron microscopy. The isolate was confirmed to be sequence type 221, with 13 putative virulence genes that are usually found in serotype 2 strains.
Conclusion:
We should be aware of the emergence of S. suis infections caused by uncommon serotypes in patients with predisposing conditions. Laboratory capacity to identify S. suis in the hospital is needed in developing countries, which can contribute to enhanced surveillance, epidemiological control, and prevention strategies in the prevalent area.
Insights
This is the first reported human case of Streptococcus suis serotype 31 infection in Thailand, highlighting the emergence of uncommon serotypes in immunocompromised individuals. Enhanced laboratory capacity is crucial for surveillance and control.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Zoonotic Pathogens
Background:
- Streptococcus suis is a zoonotic bacterium causing invasive infections in humans and pigs.
- Serotype 2 is the most common cause of human Streptococcus suis infections, with other serotypes rarely reported.
- This study documents the first human case of Streptococcus suis serotype 31 infection in Thailand.
Observation:
- A 55-year-old male with liver cirrhosis and a history of alcohol misuse presented with sepsis after consuming a raw pork product.
- Blood culture yielded an isolate identified as Streptococcus suis serotype 31, which was untypable by standard serotyping methods due to apparent loss of capsule.
- The isolate possessed virulence genes typically found in serotype 2 strains.
Findings:
- Identification of Streptococcus suis serotype 31 in a human patient in Thailand.
- Confirmation of a non-encapsulated Streptococcus suis isolate with potential virulence factors.
- Successful treatment of sepsis with ceftriaxone without complications.
Implications:
- Highlights the need for awareness regarding emerging Streptococcus suis serotypes causing human infections, especially in individuals with predisposing conditions.
- Emphasizes the importance of developing laboratory capacity for identifying Streptococcus suis in hospitals, particularly in developing countries.
- Suggests enhanced surveillance and epidemiological control strategies are necessary in prevalent areas to prevent future outbreaks.
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