Adherence of streptococcal isolates from cattle and horses to their respective host epithelial cells.

The study examined the adherence of different Streptococcal bacteria species to their respective host’s cells. It was discovered that all the species examined preferred to bind to cells of their own host species, with the type of binding linked to a plasma protein called fibronectin. Differences in how each species bonded to fibronectin were also found, potentially indicating why the bacteria adhered to their respect host cells differently.

Research overview

In this research, scientists specifically focused on the Streptococcus dysgalactiae from cattle, the S equi from horses and the S pyogenes from humans. The primary purpose was to compare how these bacteria adhere to epithelial cells of the respective host. This adherence was quantitively determined by using fluorescein-labeled streptococci.

Adherence of Streptococcus to Epithelial Cells

• Each of three streptococcal species studied displayed a unique preference for adherence to their respective host cells, i.e., Streptococcus Dysgalactiae adhered to cattle cells, S equi to horse cells, and S pyogenes to human cells.

Role of plasma protein, fibronectin

• Fibronectin, a plasma protein, plays a significant role in the adherence mechanism. All three species of streptococci were found to bind to fibronectin, though they interacted with different fragments of it.
• S. dysgalactiae and S. equi preferentially interacted with a 210-kilodalton (kD) C-terminal fragment of fibronectin, while S. pyogenes was seen to bind only with a 29-kD N-terminal fragment.

Influence of synthetic peptide, Gly-Arg-Gly-Asp-Ser

• The research team further evaluated the role of a synthetic peptide, Gly-Arg-Gly-Asp-Ser, which represents the host cell attachment site of fibronectin. The peptide partially inhibited the binding of fibronectin and its 210 kD fragment to S. dysgalactiae, but had minimal influence on S equi. It had no effect on the 29-kD fibronectin fragment of S pyogenes.

Conclusions from the research

• The differences in binding activities reflected the effectiveness of fibronectin to mediate the streptococci’s adherence to the epithelial cells. Specifically, fibronectin strongly inhibited the adherence of S. pyogenes and S. equi but only had a weak effect on S. dysgalactiae’s adherence.

Implications of the study

• These findings shed light on potential mechanisms that could explain how different streptococci species choose their respective hosts. Knowledge of these mechanisms could be significant in understanding, preventing, and treating streptococcal infections in various host organisms.