BIOLOGY 290 Lecture Notes - Lecture 7: Antimicrobial Resistance

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29 Sep 2016
Bio 209 9/20
Antibiotic resistance
- The US model of high-density agriculture—where livestock are kept in very close quarters—is an
ideal breeding ground for bacteria
- Scientists predicted in 2001 in the US:
o3 million pounds in human medicine
o24.6 million pounds in animal agriculture
o70% of the total are used for non-therapeutic uses (ie not treating a sick animal)
- Potential transmission routes from animals to humans:
oVentilation of facilities with particles in the air
oDirect contact with livestock
oContaminated soil, drinking water
oEating contaminate meat or crop fertilized with contaminated animal waste
- Some evidence that use of antibiotic in animals may increase bacterial resistance in humans
- Study done by UNC looked at wells near and far from swine production
oFound that the e coli they collected were more likely to be resistant to more drugs
oMeans there is potential of ground water and drinking water of contamination near
these facilities
- After a drug began being used in livestock, saw great increase of antibiotic resistant bacteria in
human fecal samples
- Frequency of antimicrobial resistance study saw that the poultry works vs the population had
significantly more frequency of resistant cases
- Using phylogenetic trees, it would be possible to track what the host of an organism was, and
then can look at the frequency of changes from one strain to another that might affect humans
oStudy investigated this, found that strains were much more likely to stay within one host
than have a “spillover” event, ie where bacteria changes from infecting livestock to cross
into humans; therefore these are relatively rare events
- What’s dangerous is that bacteria are freely able to exchange genetic information; so, if e coli
was made resistant, other bacteria could acquire this resistance; several different ways of this
“horizontal gene-transfer”
- Consequences of agricultural antibiotic use:
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