Antibiotics, Viruses, and Prions

Bacterial Infections• Colonization by harmful

bacteria• Using the body as resources to

grow and reproduce• Battled by the immune system• Different numbers of bacteria

needed to overwhelm the immune system and cause infection• Shigella: 10• E. coli: 100

How Antibiotics Work• 2 main methods• Kill bacteria outright• Prevent bacteria from growing

• Usually bind to bacteria to do this• Generally stop bacteria from making something• Cell wall, proteins, DNA, etc.• The more similar that target to your cells, the more toxic the

antibiotic is to you

How Antibiotics Work• Antibiotics reduce the population of invading bacteria• Survivors usually dealt with by immune system

• Start to feel better before using all of the medicine• Feel better before the population is reduced to the point that the

infection is defeated• Stopping the medication before this point leaves bacterial

survivors

Antibiotic Resistance• Surviving bacteria have time to

adapt to drug• Drug loses effect • Trait passed in population• Treatment with same drug now

ineffective

How do we deal with this?• Hospitals:• Serious infections get multiple antibiotics at the same time• Bacteria that are immune to one probably aren’t immune to the

others

• Personal: take ALL of your antibiotics as prescribed, even if you feel better before you run out of medicine• If the bottle says take for 7 days, take for 7 days, not 4

Viruses• Obligate intracellular parasites• Must invade your cells • Hijack organelles to reproduce itself

• Will antibiotics work against viruses?

NO

Viruses

Smallpox

InfluenzaEbola

Bacteriophage

Prions• Prions are misshaped proteins • When they encounter their normal counterparts, prions cause

them to refold and form into new prions, which then clump together

• Cause holes to form in the brain, giving it a spongy appearance• Cluster in spinal tissue and saliva• Mad cow disease, scrapie, Creutzfeldt-Jakob disease, kuru

Prions• No current treatment, is

100% fatal• Decontamination very

difficult• Survives bleach, heat,

concentrated bases and acids, UV

• Contamination at USAMC resulted in disposal of $300,000 worth of equipment