Novel Variant Serotype of Streptococcus suis Isolated from Piglets with Meningitis

Abstract

ABSTRACTStreptococcus suisis an emerging zoonotic pathogen causing severe infections in pigs and humans. In previous studies, 33 serotypes ofS. suishave been identified using serum agglutination. Here, we describe a novelS. suisstrain, CZ130302, isolated from an outbreak of acute piglet meningitis in eastern China. Strong pathogenicity of meningitis caused by strain CZ130302 was reproduced in the BALB/c mouse model. The strain showed a high fatality rate (8/10), higher than those for known virulent serotype 2 strains P1/7 (1/10) and 9801 (2/10). Cell adhesion assay results with bEnd.3 and HEp2 cells showed that CZ130302 was significantly close to P1/7 and 9801. Both the agglutination test and its complementary test showed that strain CZ130302 had no strong cross-reaction with the other 33S. suisserotypes. The multiplex PCR assays revealed no specified bands for all four sets used to detect the other 33 serotypes. In addition, genetic analysis of the wholecpsgene clusters of all serotypes was performed in this study. The results of comparative genomics showed that thecpsgene cluster of CZ130302, which was not previously reported, showed no homology to the gene sequences of the other strains. Especially, thewzy,wzx, and acetyltransferase genes of strain CZ130302 are phylogenetically distinct from strains of the other 33 serotypes. Therefore, this study suggested that strain CZ130302 represents a novel variant serotype ofS. suis(designated serotype Chz) which has a high potential to be virulent and associated with meningitis in animals.