Transcript Evolution In Action

Evolution In Action
The Case of the Super Bacteria
A Bad Moon Rising
According to the U.S. Centers for Disease
Control (“CDC”), the emergence and reemergence of infectious disease organisms
contributed to a 58% increase in U.S. per
capita mortality from infectious diseases
between 1980 and 1992. The incidence of
drug-resistant infections is reaching crisis
levels in many hospitals, in part because
antibiotic resistant organisms frequently lurk
in the hospital setting.
The Enemy: Bacteria
• E. coli
• Current location:
– Your stomach
– Some nasty
spinach in
Salinas
What is an antibiotic resistant
bacteria?
• A bacteria with proteins that can protect
them from the deadly effects of
antibiotics
• Basically the bacteria have genes that
give them some measure of immunity
• They survive where others are
destroyed
So what’s an antibiotic?
• The overwhelming majority of antibiotic
substances are natural products that
certain bacteria and fungi (molds)
produce and send outside of their cells.
• About 90% of the antibiotics in use
today, are isolated from bacteria.
How do antibiotics work?
• Penicillins: Inhibits formation of the
bacterial cell wall by blocking crosslinking of the cell wall structure. The cell
wall is a needed protective casing for
the bacterial cell
• Tetracyclines: Inhibit protein synthesis
by binding to the subunit of the bacterial
ribosome (30S subunit).
Testing for Effectiveness
Doesn’t
Work
Kills
‘em
good
How do
bacteria
resist
antibiotics?
How do bacteria become
resistant?
1. A mutation of their own
2. Inheriting the trait from a predecessor
3. Acquiring a plasmid from another
bacteria
4. Endocytosis of free DNA
5. Injection of resistant gene by
bacteriophage virus
Why are bacteria changing so
rapidly?
1. We use antibiotics too often, increasing
the selection pressure in favor of
resistance
2. Improper us of antibiotics (we don’t take
them as the doctor orders, allows the
strongest to survive)
3. No new class of antibiotics in 20 years
(they keep changing but we don’t)
4. Hospitals