Download Case #3: Superbug! You are called to a hospital in Dallas where a

Case #3: Superbug!
You are called to a hospital in Dallas where a mysterious bacterial infection has killed 15 patients and
sickened many more.
Your investigation:
a. Patient A was brought to the hospital for an appendectomy, and the surgery site then became
infected. The patient was treated using a second generation Penicillin-type antibiotic but quickly
deteriorated and died after just 2 days.
b. You culture the bacteria from another (still living) patient and discover it is an antibiotic-resistant
strain of Acinetobacter baumannii, a bacteria known to quickly develop resistance to many types of
antibiotics.
c. You compare DNA sequence from 100 individual cells of the resistant strain and 100 cells of the
‘normal’ strain found in most patients. You find that all 100 resistant cells are genetically identical, while
cells from the ancestral strain are quite diverse.
d. You grow both strains on agar plates containing Penicillin. Many bacterial colonies grow on the plate
with resistant bacteria, while only two colonies grow on the plate seeded with the ancestral strain.
e. You grow both strains on normal media. You find that the resistant strains grow half as fast as the
ancestral cells on normal (antibiotic-free) media.
f. You grow both strains on plates with several other antibiotics. No colonies of the Penicillin-resistant
strain grow on these plates, but 1-2 colonies of the ancestral strain grow on all plates.
In your report, you are asked to address the following:
1) Why was the resistant strain less genetically diverse than the non-resistant strain?
2) What does it tell you that some cells from the ancestral strain still grew on Penicillin and on plates
with other antibiotics?
3) Why do you think the resistant strain grows more slowly than the more diverse ancestral strain on
normal media?
4) What evolutionary forces were at work in this hospital? Where does antibacterial resistance in A.
baumannii come from?
5) Suggest at least two strategies for addressing this problem.
6) What risks are involved with each strategy?