Genotypic profile of Streptococcus suis serotype 2 and clinical features of infection in humans, Thailand

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.

Figure 1

A) Pulsed-field gel electrophoresis profiles of 165 human isolates of Streptococcus suis serotype 2, after SmaI digestion. Numbers of isolates are indicated in parentheses below pulsotype numbers. B) Dendrogram generated from the pulsed-field gel electrophoresis profiles. ST, sequence type.

Figure 2

Distribution and sequence types (STs) of 165 human isolates of Streptocoocus suis serotype 2, January 2006–August 2008, Thailand. A) Regions of isolation; B) monthly distribution of isolations.