Haiqing Yu, Nan Wang, Hong Yu, Qiong Hong and Hongmin Sun
University of Missouri, USA
Posters & Accepted Abstracts: J Med Microb Diagn
Streptococcus pyogenes is a common clinical pathogenic bacterium and 1800 invasive S. pyogenes disease-related deaths are reported in the USA yearly; among which, streptococcal toxic shock syndrome has a mortality rate of 30-70%. Pharmacological studies showed that Oridonin, a natural product of Rabdosia rubescens herb, has antimicrobial activities. However, the underlying mechanism of Oridonin in blocking Streptococcus pyogenes is still obscure. In the current study, Streptococcus pyogenes strain ATCC 19615 (serotypes 5 and 49) was treated with 50 ├?┬╝M Oridonin for 20 hours and the secretion proteins with differential expression were identified and analyzed by SDS-PAGE and LC-MS/MS, respectively. The expression level of differential gene was analyzed via using quantitative RT-PCR (qRT-PCR) and western blot. Based on an intraperitoneal injection mouse model with 6-8├?┬?109 CFU, the virulence of S. pyogenes was investigated between DMSO group and Oridonin group by counting the CFU in spleen. The results indicated that (1) SDS-PAGE and LC-MS/MS analysis indicated that SpeB (Streptococcal Pyrogenic Exotoxin B) was significantly decreased in Oridonin group (p<0.01). (2) qRT-PCR data showed that the transcriptional levels of SpeB, LuxS (activator), LacD1 (repressor) and Eno (chaperone) were dramatically decreased (p<0.01). The western blot analysis indicated that the maturation and processing of SpeB were blocked by Oridonin (p<0.01). (3) The spleen CFU of S. pyogenes were reduced in Oridonin group (p<0.05). Our result suggests that Oridonin is a novel inhibitor of SpeB and it regulates virulence in Streptococcus pyogenes.