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Published on: July 1, 2018
Clonal dissemination of human isolates of Streptococcus suis serotype 14 in Thailand
Anusak Kerdsin1, Kazunori Oishi2, Saowalak Sripakdee1
1National Institute of Health, Department of Medical Sciences, Ministry of Public Health, Tiwanon Road, Muang, Nonthaburi 11000, Thailand.
Abstract:
Most cases of Streptococcus suis infection in humans are caused by serotype 2 strains, and only a few cases caused by other serotypes have been reported. Among 177 human isolates of S. suis in Thailand, 12 (6.8 %) were identified as being of serotype 14, and an occurrence of sporadic S. suis serotype 14 infection was noted during 2006-2008, particularly in northern Thailand. Clinical presentations of the 12 patients (median age 62.9 years) included meningitis (58.3 %), septic arthritis (25 %) and sepsis (16.7 %). These clinical features were similar to those previously reported for S. suis infections, except that there were no fatal cases. All of the 12 serotype 14 strains belonged to the multilocus sequence types (ST) 105 (n=11) and the novel ST127 (n=1). Molecular typing by PFGE revealed four different pulsotypes, including an identical pattern for nine ST105 strains and three closely related patterns for two ST105 strains and one ST127 strain. Our PFGE data suggested clonal dissemination of ST105 strains in Thailand. Because serotype 14 is becoming a more common cause of S. suis infections in humans, diagnostic tests for serotype 14 should be performed in South-East Asian countries.
Insights
Streptococcus suis serotype 14 is an emerging cause of human infections in Thailand, primarily presenting as meningitis and septic arthritis. Early diagnostic tests for this serotype are recommended in Southeast Asia.
Area of Science:
- Microbiology
- Infectious Diseases
- Epidemiology
Background:
- Streptococcus suis (S. suis) infections in humans are predominantly caused by serotype 2 strains.
- Other serotypes are rarely reported, but an increase in serotype 14 infections has been observed.
Purpose of the Study:
- To investigate the occurrence and characteristics of Streptococcus suis serotype 14 infections in humans in Thailand.
- To analyze the molecular epidemiology of these S. suis serotype 14 isolates.
Main Methods:
- Analysis of 177 human S. suis isolates from Thailand.
- Identification of serotypes, including serotype 14.
- Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) for molecular characterization.
Main Results:
- Twelve (6.8%) of the human S. suis isolates were identified as serotype 14.
- Clinical presentations included meningitis (58.3%), septic arthritis (25%), and sepsis (16.7%), with no fatal cases.
- MLST identified ST105 (11 isolates) and a novel ST127 (1 isolate). PFGE revealed clonal dissemination of ST105 strains.
Conclusions:
- Serotype 14 is an emerging cause of S. suis infections in Thailand.
- Diagnostic tests for S. suis serotype 14 should be considered in Southeast Asian countries.
- Molecular data suggest clonal spread of specific S. suis serotype 14 strains.
