What is the expected outcome of increased H2O2 production by S. pneumoniae on host cells?

• A. Enhanced cell survival
• B. Induced apoptosis
• C. Stimulation of cell division
• D. Decreased immunogenic response

Answer: (B)

Increased production of hydrogen peroxide (H2O2) by Streptococcus pneumoniae can lead to induced apoptosis in host cells. Hydrogen peroxide is a reactive oxygen species (ROS), which can cause oxidative stress in cells. This oxidative damage can trigger various cellular pathways that ultimately lead to apoptosis, or programmed cell death.

When S. pneumoniae produces higher levels of H2O2, it can overwhelm cellular antioxidant defenses, leading to the activation of apoptotic signaling cascades. This process typically involves the release of cytochrome c from mitochondria, activation of caspases, and subsequent cell death.

Additionally, the effect of H2O2 on host cells is a strategy employed by some pathogens to undermine the immune response, as damaged or dead host cells can alter the dynamics of the immune response, providing a survival advantage to the pathogen. Thus, the generation of H2O2 by S. pneumoniae results in detrimental effects that favor apoptosis of host cells.