Expression and diversity of the sialic acid–binding adhesin and its homologs associated with oral streptococcal infection

Abstract

Streptococcus gordonii, one of the early colonizers of oral biofilms, is involved in the development of dental caries, periodontal disease, and infective endocarditis. The Hsa adhesin of S. gordonii DL1 has the ability to bind strongly to the terminal sialic acid groups of host glycoproteins via the binding region, nonrepetitive region 2 (NR2), which is important for the pathogenicity of S. gordonii DL1. Low similarity with the NR2 of Hsa homologs among other streptococcal species has been reported. However, the reports have been limited to certain strains. This study attempted to assess frequency of the expression on the bacterial cell surface and to analyze the diversity of Hsa homologs among different wild strains of oral streptococci. We isolated 186 wild-type strains of oral streptococci from healthy volunteers and analyzed their hemagglutinating (HA) activity on human erythrocytes and their Hsa homologs and NR2 homologous regions by dot immunoblotting using anti-Hsa and anti-NR2 antisera, respectively. We found 30 strains reacted with anti-NR2 antiserum (NR2 positive) and determined the sequence of the NR2 regions. Many strains with high HA activity were also NR2 positive, suggesting that the NR2 region may be associated with HA activity. Among the NR2-positive strains, four different amino acid sequence patterns were observed, demonstrating diversity in the NR2 region. Notably, S. gordonii strains frequently possessed Hsa homologs and NR2-like antigens compared with other streptococci. It is speculated that the possessing frequency of Hsa homologs and the amino acid sequence of NR2 region may vary among streptococcal species.

Monitoring Salivary Sialic Acid and Sialidase Activity to Assess Oral Health Status: Results of a Single Site Double-Blind Study

“…For example, Streptococcus gordonii, a gram-positive bacterium that is identified as an early colonizer of oral biofilms has SA binding regions. A recent study evaluated 186 clinical strains of S. gordonii, collected from human subjects and reported variations in SA binding regions [6,7]. Whereas the specific clinical outcomes of these variations remain unclear, it is possible that these variations likely contribute to the factors that influence the progression of disease.…”

“…Furthermore, the sialic acid found in the glycans of the exposed epithelial surfaces of oral, gut and other mucosal barriers serves as a source of energy for microbial growth and the initial steps of microbial pathogenesis. For instance, it is estimated that more than 70 different oral organisms utilize exogenous sialic acid [7] and is known to stimulate the growth of organisms such as Tannerella forsythia [8,10].…”

“…Due to their critical role in membrane function SA are referred to as cytoprotectants with multiple functions [1,[3][4][5] and serve as masks and ligands [5,6]. Sialidases are enzymes produced by organisms to liberate the sialic acid with the influenza virus representing the earliest and best-categorized system [5][6][7][8]. The free sialic acid is identified as a nutritional component for organisms and mucosal colonization [6][7][8][9][10].…”

“…Sialidases are enzymes produced by organisms to liberate the sialic acid with the influenza virus representing the earliest and best-categorized system [5][6][7][8]. The free sialic acid is identified as a nutritional component for organisms and mucosal colonization [6][7][8][9][10].…”