Which experiment would most effectively link prior results to show that S. pneumoniae can induce apoptosis by causing double-strand breaks (DSBs)?

• A. Measure levels of H2O2 produced by each strain
• B. Determine factors secreted by each strain
• C. Find out if H2O2 is produced by different strains of S. pneumoniae
• D. Measure the number of DSBs in AECs with each strain

Answer: (D)

To effectively link prior results and demonstrate that S. pneumoniae can induce apoptosis by causing double-strand breaks (DSBs), measuring the number of DSBs in airway epithelial cells (AECs) infected with each strain directly addresses the core mechanism in question. This experiment focuses on quantifying the actual occurrence of DSBs, which is a crucial step in confirming that S. pneumoniae, through its pathogenicity, is indeed causing this specific form of cellular damage associated with apoptosis.

By assessing the number of DSBs, the experiment establishes a direct connection between the presence of S. pneumoniae and the resultant cellular damage leading to apoptosis. This gives clear evidence supporting the hypothesis regarding the pathogen's virulence factors and their effects on host cells.

Other approaches, while valuable in their own contexts, do not provide the same direct linkage. For example, measuring levels of H2O2 or identifying factors secreted by each strain might help understand the infection dynamics or the injury mechanisms involving reactive oxygen species, but they do not quantify the specific cellular damage in terms of DSBs. Thus, they are less effective in directly demonstrating the induction of apoptosis through this particular pathway.