Inactivation of SARS-CoV-2 by Catechins from Green Tea.

Green tea extracts effectively inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in vitro in a dose-dependent manner. Ten-fold serially diluted solutions of catechin mixture reagent from green tea were mixed with the viral culture fluid at a volume ratio of 9:1, respectively, and incubated at room temperature for 5 min. The solution of 10 mg/mL catechin reagent reduced the viral titer by 4.2 log and 1.0 mg/mL solution by one log. Pre-infection treatment of cells with the reagent alone did not affect viral growth. In addition, cells treated with only the reagent were assayed for host cell viability using the WST-8 system, and almost no host cell damage by the treatment was observed. These findings suggested that the direct treatment of virus with the reagent before inoculation decreased the viral activity and that catechins might have the potential to suppress SARSCoV-2 infection.

Defining the taxonomic status of Streptococcus suis serotype 33: the proposal for Streptococcus ruminantium sp. nov.

To clarify the taxonomic classification of Streptococcus suis serotype 33, we performed biochemical and molecular genetic analyses using isolates (GUT-183, GUT-184, GUT-185, GUT-186, GUT-187T, GUT-188, GUT-189, GUT-190, GUT-191, GUT-192 and GUT-193) from bovine endocarditis. A comparative sequence analysis showed 99.2-100 % sequence similarity among the reference strain of S. suis serotype 33 and our isolates for the 16S rRNA gene. These similarities were higher than those between the isolate GUT-187T and S. suis and other streptococci. Comparison of sodA genes also showed high degrees of similarities among the reference strain of S. suis serotype 33 and our isolates (99.7-100 %), which were higher than those between the GUT-187T and S. suis and other streptococci. DNA-DNA relatedness among three isolates (GUT-186, GUT-187T, the reference strain of S. suis serotype 33) was over 76.7 %. In contrast, the relatedness between GUT-187T and the other streptococcal species (S. suis, Streptococcus parasuis, Streptococcus acidominimus and Streptococcus porci) was 8.4-24.9 %. Phylogenetic analyses showed that the isolates did not affiliate closely to any known species of the genus Streptococcus. Moreover, GUT-187T could be distinguished from S. suis and other closely related species of genus Streptococcus using biochemical tests. On the basis of the phenotypic and molecular genetic data, we propose that the isolates of S. suis serotype 33 should be classified into the genus Streptococcus, Streptococcus ruminantium sp. nov. with the type strain GUT-187T (=DSM 104980T=JCM 31869T).

Human Rickettsia heilongjiangensis infection, Japan.

A case of Rickettsia heilongjiangensis infection in Japan was identified in a 35-year-old man who had rash, fever, and eschars. Serum contained R. heilongjiangensis antibodies, and eschars contained R. heilongjiangensis DNA. R. heilongjiangensis was also isolated from ticks in the suspected geographic area of infection.

rDNA sequence analyses of Streptococcus dysgalactiae subsp. equisimilis isolates from pigs.

The nucleotide sequences of 16S and 23S rRNA genes (rDNA) were determined for 11 isolates of Streptococcus dysgalactiae subsp. equisimilis from slaughtered pigs with endocarditis, arthritis or lymphadenitis and strain ATCC 35666, designated as a strain of subspecies equisimilis. The sequences of each of the genes were compared phylogenetically with the corresponding sequences of S. dysgalactiae subsp. dysgalactiae ATCC 43078(T) and ATCC 27957, which were also determined in this study. Based on the 16S rDNA analysis, the isolates of S. dysgalactiae subsp. equisimilis were divided into two distinct groups, designated groups 1 and 2. S. dysgalactiae subsp. equisimilis ATCC 35666 was closely related to the group 2 strains. The S. dysgalactiae subsp. dysgalactiae strains seemed to be associated with the group 1 strains, which was not consistent with the conventional subspecific classification of S. dysgalactiae. In contrast, the 23S rDNA analysis distinguished S. dysgalactiae subsp. dysgalactiae strains from subsp. equisimilis strains. This inconsistency between phylogenies based on 16S and 23S rDNA indicates that 23S rDNA is a more rigid marker for determining the phylogenetic relationships and taxonomic position of these organisms than is 16S rDNA.

Streptococcus dysgalactiae-derived mitogen (SDM), a novel bacterial superantigen: characterization of its biological activity and predicted tertiary structure.

A mitogenic substance, designated Streptococcus dysgalactiae-derived mitogen (SDM), was purified from S. dysgalactiae culture supernatant, and the gene encoding the mitogen was cloned. Both native and recombinant SDM expressed in Escherichia coli significantly activated human V beta 1+ and V beta 23+ T cells in association with major histocompatibility complex (MHC) class II molecules on accessory cells, indicating that SDM possesses superantigenic properties. The sdm gene consists of two segments encoding a signal peptide and a mature 25 kDa protein composed of 212 amino acids. Three of 34 S. dysgalactiae strains but none of 28 Streptococcus pyogenes strains examined carried sdm. Phylogenetic analysis indicated that SDM belongs to a family distinct from established bacterial superantigens. SDM showed around 30% homology with other superantigens at the amino acid sequence level. The tertiary structure of SDM was predicted by modelling onto streptococcal pyrogenic exotoxin C and streptococcal mitogenic exotoxin Z-2, both of which share highly homologous structure-determining regions. SDM showed overall structural similarity to both these superantigens. This is the first study to characterize fully a bacterial superantigen from S. dysgalactiae.