Streptococcus suis Serotype 2, Thailand | CDC EID

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Volume 17, Number 5–May 2011
Research
Genotypic Profile of Streptococcus suis Serotype 2 and Clinical Features of Infection in Humans, Thailand
Anusak Kerdsin, Surang Dejsirilert, Parichart Puangpatra, Saowalak Sripakdee, Koranan Chumla, Nitsara Boonkerd, Pitimol Polwichai, Susumu Tanimura, Dan Takeuchi, Tatsuya Nakayama, Shota Nakamura, Yukihiro Akeda, Marcelo Gottschalk, Pathom Sawanpanyalert, and Kazunori Oishi

Author affiliations: Ministry of Public Health, Nonthaburi, Thailand (A. Kerdsin, S. Dejsirilert, P. Puangpatra, S. Sripakdee, K. Chumla, N. Boonkerd, P. Polwichai, P. Sawanpanyalert); Naresuan University Phayao Campus, Phayao, Thailand (N. Boonkerd); Hyogo College of Medicine, Nishinomiya, Japan (S. Tanimura); Osaka University, Osaka, Japan (D. Takeuchi, T. Nakayama, Y. Akeda, K. Oishi); Thailand-Japan Research Collaboration Center for Emerging and Re-emerging Infections, Nonthaburi (S. Nakamura); and University of Montreal, Quebec, Canada (M. Gottschalk)


Suggested citation for this article


Abstract
To examine associations between clinical features of Streptococcus suis serotype 2 infections in humans in Thailand and genotypic profiles of isolates, we conducted a retrospective study during 2006–2008. Of 165 patients for whom bacterial cultures of blood, cerebrospinal fluid, or both were positive for S. suis serotype 2, the major multilocus sequence types (STs) found were ST1 (62.4%) and ST104 (25.5%); the latter is unique to Thailand. Clinical features were examined for 158 patients. Infections were sporadic; case-fatality rate for adults was 9.5%, primarily in northern Thailand. Disease incidence peaked during the rainy season. Disease was classified as meningitis (58.9%) or nonmeningitis (41.1%, and included sepsis [35.4%] and others [5.7%]). Although ST1 strains were significantly associated with the meningitis category (p< 0.0001), ST104 strains were significantly associated with the nonmeningitis category (p< 0.0001). The ST1 and ST104 strains are capable of causing sepsis, but only the ST1 strains commonly cause meningitis .


Streptococcus suis, an emerging zoonotic pathogen, causes invasive infections in persons who are in close contact with infected pigs or contaminated pork-derived products (1). On the basis of capsular polysaccharides, 33 serotypes of S. suis have now been identified. Of these, serotype 2 is the most prevalent type in humans infected with this pathogen (1,2). Since the largest outbreak of human S. suis infection in 2005, in Sichuan Province, People's Republic of China (3), this disease has been increasingly recognized worldwide. The numbers of reported cases, especially in persons from Southeast Asian countries, have increased dramatically during past few years (4).

In Thailand, at least 300 cases of S. suis infection in humans have been reported (5–11). Although an outbreak of S. suis infections was confirmed in Phayao Province during May 2007 (9), most cases in humans occur sporadically and are primarily located in the northern region of this country (6–11). A relatively low incidence of cases with S. suis serotype 14 has also been reported in this region (12). Although previous studies have reported high frequencies (59.0%–88.7%) of S. suis infections in persons in this area who ate raw pork products (8–11), the pathogenesis of this disease, including routes of transmission, is unclear.

The major clinical manifestations of the disease are bacterial meningitis and sepsis, but other manifestations have been reported (1,4,8,10,13). Most cases of bacterial meningitis can be attributed to the hematogenic spread of invasive bacteria, but how circulating bacteria cross the blood–cerebrospinal fluid (CSF) barrier and cause meningitis is not clear (14,15). Furthermore, the overall clinical features of this disease have not been extensively and comprehensively investigated in Southeast Asian countries.

A variety of virulence factors associated with S. suis have been reported (16–20), but none have been proven to be essential for the host defense of this disease, except the capsular polysaccharide (19). In serotype 2 isolates obtained during a previous outbreak in Sichuan, China, an ≈89-kb DNA fragment, which has been associated with a pathogenicity island (89K PAI), was identified (21). The 89K PAI fragment encodes a 2-compartment signal transduction system, SalK-SalR, which is required for full virulence (22).

We report the results of a retrospective study of the clinical features of 158 cases of human infection with S. suis serotype 2 and the molecular epidemiology of 165 S. suis serotype 2 isolates. The study objective was to demonstrate associations between the clinical features of disease caused by S. suis serotype 2 in persons in Thailand and the genotypic profiles of the isolates. The study was reviewed and approved by the Ethics Committees of Research Institute for Microbial Diseases, Osaka University, and conducted according to the principles expressed in the Declaration of Helsinki.

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Streptococcus suis Serotype 2, Thailand | CDC EID


Suggested Citation for this Article
Kerdsin A, Dejsirilert S, Puangpatra P, Sripakdee S, Chumla K, Boonkerd N, et al. Genotypic profile of Streptococcus suis serotype 2 and clinical features of infection in humans, Thailand. Emerg Infect Dis [serial on the Internet]. 2011 May [date cited] .
http://www.cdc.gov/EID/content/17/5/835.htm


DOI: 10.3201/eid1705.100754


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Kazunori Oishi, Laboratory for Clinical Research on Infectious Diseases, International Research Center for Infectious Diseases, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita565-0871, Japan; email: oishik@biken.osaka-u.ac.jp