Streptococcus Suis : A New Emerging or an Old Neglected Zoonotic Pathogen?

Abstract

Infections caused by Streptococcus suis are considered a global and an economical problem in the swine industry. Moreover, S. suis is an agent of zoonosis that afflicts people in close contact with infected pigs or pork-derived products. Although sporadic cases of S. suis infections in humans (mainly meningitis) have been reported during the last 40 years, a large outbreak due to this pathogen emerged in the summer of 2005 in China. The severity of the infection in humans during the outbreak, such as a shorter incubation time, more rapid disease progression and higher rate of mortality, attracted a lot of attention from the scientific community and the general press. In fact, the number of publications on S. suis (including the number of reported human cases) has significantly increased during recent years. In this article we critically review the present knowledge on S. suis infection in humans, we discuss the hypotheses that may explain the 2005 outbreak and the repercussion of such an episode on the scientific community.

Predominance of Streptococcus suis ST1 and ST7 in human cases in China, and detection of a novel sequence type, ST658

“…A recent review shows that most strains isolated from humans are phenotypically and genotypically similar to those recovered from pigs within the same geographical region. 9 However, the present finding of a major difference in the number of sequence types of S. suis from humans (n D 4; ST1, ST7, ST377 and ST658) compared with the 354 sequence types from pigs in China was unexpected. Although the reason for this discrepancy is unclear, it is possible that sampling bias may play a role.…”

“…1A). It is notable that sequence types ST1 and ST7 predominate in mainland China, and ST7, recognized to be a highly virulent and linked to the largest S. suis outbreak, 9 did not appear to spread substantially since the outbreak of 2005.…”

“…4 It is striking that ST377 and ST658 were found exclusively in humans (not pigs), which is interesting considering S. suis is a zoonotic pathogen primarily and usually found in pigs, but with no direct evidence to date showing human-to-human infection. 9 Therefore, future work should focus on a broader sampling from humans (from different countries in Asia) and comparative analyses with S. suis from pigs.…”

“…The eBURST analysis assigned ST658 to the ST1 complex, which also contains ST7. 4,9 The ST1 complex represents principally human cases associated with septicaemia and meningitis in pigs and humans in different parts of the world. 4,9 The genome of S. suis LSM102 was sequenced using PacBio RS II (250-fold coverage) and Illumina HiSeq 2500 (400-fold coverage).…”

“…4,9 The ST1 complex represents principally human cases associated with septicaemia and meningitis in pigs and humans in different parts of the world. 4,9 The genome of S. suis LSM102 was sequenced using PacBio RS II (250-fold coverage) and Illumina HiSeq 2500 (400-fold coverage). 10 First, de novo assembly of the sequencing reads from PacBio RS II was carried out using SMRT Analysis software (https://github.com/PacificBiosciences/SMRT-Analysis/ wiki/SMRT-Pipe-Reference-Guide-v2.3.0).…”