Question

Table 5. Use of antibiotics to clear pneumococcal meningitis infection.
drug treatment	% of mice who died	Number of S. pneumoniae present in meninges samples after drug treatment
None	61	105/ml
Methicillin	95	0
streptomycin	60	105/ml
dexamethasone	65	105/ml
methicillin plus dexamethasone	2	0
streptomycin plus dexamethasone	63	105/ml

9. Fredrica has been looking into the effectiveness of various drug treatments to cure people who have life- threatening streptococcal infections. The data in the table 5 quantify the success (or lack of success) for five different drug treatments used to treat mice who had pneumococcal meningitis (infection of the membranes covering the brain and spinal cord by S. pneumoniae). Use this information to answer questions 9a –9c.

9a. (1 pt) Which of the drug treatments were effective in killing the etiologic agent?

9b. (2 pts) One of the treatments caused a significant increase in the mouse mortality rate.   Which one?

Provide a reasonable explanation for this increase.

9c. (3 pts) Which treatment should Fredrica recommend for treating infected patients? Why is this treatment effective? What is/are the role(s) of the drug(s)?

Answer 1

9a.

Methicillin treatment is effective in killing etiologic agent.

Treatment with this drug completely eliminated S. pneumonia in meninges samples.

9b.

Methicillin treatment caused significant increase in mortality. Methicillin killed bacteria. This results in release of bacterial components which lead to production of the inflammatory cytolines, interleukin-1 and tumor necrosis factor in the subarachnoid space. This causes a cascade of events leading to coma, stroke, seizures and other complications that cause death.

9c.

Fredrica should recommend methicillin plus dexamethasone. It is effective in clearing bacteria and reducing mortality.

Methicillin killed bacteria. It is antibiotic.

Dexamethasone inhibits synthesis of IL-1 and TNF and decreases CSF outflow resistance and stabilizes blood brain barrier. This will prevent the complications caused by the bacterial components released after death caused by methicillin.