One hundred and two Streptococcus agalactiae (group B streptococcus [GBS]) isolates were collected from dairy cattle with subclinical mastitis in Eastern China during 2011. Clonal groups were established by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE), respectively. Capsular polysaccharides (CPS), pilus and alpha-like-protein (Alp) family genes were also characterized by molecular techniques. MLST analysis revealed that these isolates were limited to three clonal groups and were clustered in six different lineages, i.e. ST (sequence type) 103, ST568, ST67, ST301, ST313 and ST570, of which ST568 and ST570 were new genotypes. PFGE analysis revealed this isolates were clustered in 27 PFGE types, of which, types 7, 8, 14, 15, 16, 18, 23 and 25 were the eight major types, comprising close to 70% (71/102) of all the isolates. The most prevalent sequence types were ST103 (58% isolates) and ST568 (31% isolates), comprising capsular genotype Ia isolates without any of the detected Alp genes, suggesting the appearance of novel genomic backgrounds of prevalent strains of bovine S. agalactiae. All the strains possessed the pilus island 2b (PI-2b) gene and the prevalent capsular genotypes were types Ia (89% isolates) and II (11% isolates), the conserved pilus type providing suitable data for the development of vaccines against mastitis caused by S. agalactiae.

Streptococcus suis serotype 2 is a major pathogen of swine streptococcicosis, which result in serious economic loss worldwide. SS2 is an important zoonosis causing meningitis, septicemia and even death in humans. Neutrophil extracellular traps (NETs) constitute a significant bactericidal strategy of innate immune. The battle between SS2 and NETs may account for the pathogenicity of SS2. However, the molecular mechanism underlying release of SS2-induced NETs remains unclear. In this study, SS2 was found to induce NETs within 2-4 h, and was dependent on reactive oxygen species (ROS) from NADPH oxidase. Moreover, SS2 could activate neutrophil p38 MAPK and ERK1/2. Blockage of p38 MAPK or ERK1/2 activation decreased SS2-induced NETs formation by 65% and 85%, respectively. In addition, NADPH oxidase derived ROS inhibition negatively affected phosphorylation of p38 MAPK and ERK1/2 in SS2 induced neutrophils. Both TLR2 and TLR4 were obviously up-regulated by SS2 infection in blood cells in vivo and neutrophils in vitro, which indicates these two receptors are involved in SS2 recognition. Blocking TLR4 signaling could further inhibit the activation of ERK1/2, but not p38 MAPK; however, TLR4 signaling inhibition reduced NETs formation induced by SS2. In conclusion, SS2 could be recognized by TLR2 and/or TLR4, initiating NETs formation signaling pathways in a NADPH oxidase derived ROS dependent manner. ROS will activate p38 MAPK and ERK1/2, which ultimately induces NETs formation.