Invasive Disease and Toxic Shock due to Zoonotic Streptococcus suis: An Emerging Infection in the East?

S treptococcus suis (S. suis) is widely recognised in the veterinary world as a cause of rapidly progressive and fatal sepsis in infant pigs, associated with meningitis, polyarthritis, and, occasionally, pneumonia. A more fulminant bacteraemic infection is seen in neonatal pigs [1,2]. For reasons that are unknown, adult pigs do not succumb to this infection, although they demonstrate asymptomatic nasopharyngeal carriage (Figure 1), and infant piglets become infected after early contact with colonised adult females. In many respects, S. suis infection is the porcine version of human group B strep disease. Zoonotic disease due to S. suis does occur sporadically in Western countries, but is encountered more commonly in countries such as Thailand, China, and Hong Kong. It affects predominantly individuals with occupational exposure to pigs. In humans, meningitis is the most common presentation (about 80% of all cases), though S. suis disease can be associated with other suppurative complications such as pneumonia and arthritis. Mortalities of 5%–10% of cases are reported [2], and S. suis is the third most common cause of bacterial meningitis in Hong Kong [3]. In the current issue of PLoS Medicine, Tang and colleagues report on the largest known zoonotic outbreak of S. suis , which occurred in Sichuan Province in China in 2005 [4]. The outbreak, which attracted considerable public and scientifi c interest [5], killed 38 out of 204 individuals with the infection and coincided with a major outbreak of disease in pigs. In addition to its size and the associated high mortality, this outbreak is unique in that a large proportion of patients were victim to a toxic shock-like syndrome (TSLS). Indeed, the vast majority of deaths in this outbreak occurred in patients with TSLS rather than in patients with meningitis. To date, streptococcal toxic shock, per consensus defi nition, has been limited to disease caused by the group A streptococcus, S. pyogenes [6]. Sporadic reports of TSLS due to other (nongroup A) beta-haemolytic streptococci have been reported, though there is potentially considerable diagnostic overlap between cases of septic shock and TSLS [7]. With one exception [8], S. suis has not previously been linked to TSLS. Tang and colleagues report that almost all human cases of TSLS due to S. suis demonstrated an erythematous blanching rash, one of the most specifi c features of TSLS, associated with hypotension and multiorgan failure. Tang and colleagues provide insight into the clinical outbreak with regard …