What is the Primary Determinant of Virulence in Streptococcus Pneumoniae

Question

What is the primary determinant of virulence in Streptococcus pneumoniae?
A) the presence of a particular Lancefield antigen
B) the production of pneumolysin
C) the presence of a polysaccharide capsule
D) the ability to lyse red blood cells
E) strain-specific teichoic acids in its cell wall

Accepted Answer

The presence of a polysaccharide capsule is the primary determinant of virulence in Streptococcus pneumoniae. The capsule provides defense against phagocytosis by the host's immune cells and allows the bacteria to evade the host's defenses, leading to more severe infections.

Answer: B
 The production of pneumolysin is an important factor in the virulence of Streptococcus pneumoniae. Pneumolysin is a toxin that damages host cells, disrupts the respiratory epithelium, and contributes to the bacterial invasion and colonization of host tissues. However, it is not the primary determinant of virulence in S. pneumoniae.

Answer: A, D, E
 The presence of a particular Lancefield antigen, the ability to lyse red blood cells, and strain-specific teichoic acids in its cell wall are not primary determinants of virulence in Streptococcus pneumoniae. Lancefield antigens are used to classify streptococci into groups based on their cell wall composition. Lysis of red blood cells is commonly seen in S. pneumoniae, but it is not required for virulence. Teichoic acids are important components of the cell wall in many gram-positive bacteria, including S. pneumoniae, but their role in virulence is not well understood.