[eas78]

A sample of cloudy cerebrospinal fluid (CSF) from a suspected meningitis case arrives and you are told to Gram stain it, and then to plate it on blood agar and chocolate agar. In the Gram stain you find gram-negative rods of varying size and shape. You also find a lot of bacteria inside phagocytic cells. They are not diplococci. Colonies grown on both of the plates you inoculated.
Later, the charge nurse tells you that the patient, a 3-year-old girl, has not received any childhood vaccinations.

1. Name some organisms that are the possible etiologic agents of this disease.
2. How does the Gram stain help you determine a specific likely causative organism?
3. How is chocolate agar different from blood agar?
4. Why did the clinical lab plate the specimen on blood agar and chocolate agar? Which of the possible etiologic agents will grow on blood agar? Which will grow on chocolate agar?
5. The organism present in the CSF was the first organism whose entire genome (DNA) sequence was determined. What is the probable shape of this bacterium's genome(chromosome)? Why is knowing the DNA sequence of the chromosome important? What could this information be used for?