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Genotypic diversity of Streptococcus suis strains isolated from humans in Thailand

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European Journal of Clinical Microbiology & Infectious Diseases Aims and scope Submit manuscript


The purpose of this study is to characterize Streptococcus suis isolates recovered from human infections regarding serotype distribution, genotypic profile, clinical manifestations, and epidemiology. A total of 668 S. suis isolates recovered from human infections in Thailand were characterized based on serotyping by multiplex PCR and co-agglutination, genotypic profiles by multilocus sequence typing, and PCR for virulence-associated genes, as well as review of medical records. Serotype 2 (94.6%) was predominant, followed by serotype 14 (4.5%), 24 (0.45%), 5 (0.3%), and 4 (0.15%). Multilocus sequence typing analyses revealed seven clonal complexes (CC): CC1 (56.43%), CC104 (31.74%), CC233/379 (5.4%), CC25 (4.5%), CC28 (0.9%), CC221/234 (0.6%), CC94 (0.15%), and two singletons. The CC1 group contained serotype 2 and 14 isolates, while CC25, 28, 104, and 233/379 consisted of serotype 2 isolates only. CC221/234 contained serotype 5 and 24 isolates, whereas the single serotype 4 isolate belonged to CC94. Two singletons contained serotype 5 (ST235) and 2 (ST236) isolates. Our data showed that ST1 isolates were more associated with meningitis than those of other STs (p < 0.001). The major route of infection was shown to be close contact with infected pigs or contaminated raw pork-derived products, including occupational exposure and recent consumption of raw pork products. This study revealed a relatively large number of CCs of S. suis causing human infection in Thailand. Among them, CC1 followed by CC104, with serotype 2 isolates, are predominant. Food safety campaigns and public health interventions would be important for controlling the S. suis infection in humans.

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We thank J. P. Auger for reviewing the manuscript.


All authors have read and approved the final article. AK, YA, DT, and KO participated in the conception and design of the study and analysis and interpretation of data. AK, MG, and KO drafted the manuscript. All authors have final approval of the version to be submitted.


This study was funded by the Japan Society for the Promotion of Science (KAKENHI 21406027) and Japan Initiative for a Global Research Network on Infectious Diseases launched by the Ministry of Education, Science, and Culture of Japan.

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Correspondence to Anusak Kerdsin.

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This study was reviewed and approved by the Ethics Committees of the Department of Medical Sciences, Ministry of Public Health, Thailand. Medical record reviews were conducted by the medical doctors under the protocol approved by the Ethics Committees.

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The authors declare that they have no conflict of interest.

Electronic supplementary material


Distribution and sequence types (STs) of Streptocoocus suis in each region in Thailand. (JPEG 215kb)


Case distribution between northern Thai cases and whole country cases. (JPEG 201kb)

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Kerdsin, A., Akeda, Y., Takeuchi, D. et al. Genotypic diversity of Streptococcus suis strains isolated from humans in Thailand. Eur J Clin Microbiol Infect Dis 37, 917–925 (2018).

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