infections and disease

What is the germ theory of disease?

microorganisms cause disease

Antoni van Leeuwenhoek (1632-1723)

first to describe bacteria, further progress required development of more powerful microscopes

John Snow and Cholera

Cholera epidemics in London, mid 1850s

Suspected an association with water supply, which came from the Thames River

"Natural experiment"

Questioned households where a cholera death had occurred

Most deaths associated with one company

What are Koch's postulates?

1. The same pathogen must be present in every case of the disease.

2. The pathogen must be isolated from the diseased host and grown in pure culture.

3. The pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible laboratory animal.

4. The pathogen must be isolated from the inoculated animal and must be shown to be the original organism.

what are the main types of microbes and where are they located

bacteria (literally everywhere)

Pathogenic bacteria

bacteria that cause disease

Nonpathogenic bacteria

Bacteria that do not cause disease. commensals or microflora

virulence factors

traits of a microbe that promote pathogenicity

Ways that Bacteriacan cause disease

Being in a location in our bodiesthat they don't normally occupy

virulence factors

Taking advantage of an "opportunity"

Microbiota shift disease- Antibiotic treatment destroys our microflora and gives pathogenic bacteria an opportunity to take over

Protists

Mostly unicellular organisms with very different life cycles, modes of locomotion & cellular structure

Many mammals, including beaver, cattle & dogs can carry this parasite and contaminate water sources

Fungus and moulds

single-celled microbes

Mycorrhizal associations

symbiotic interactions with soil fungi that increase a plant's ability to absorb minerals

mycosis

fungal infection

filamentous fungus

Widespread in nature, commonly seen on stale bread, cheese & fruit-

Plays an important role in the biodegradation of natural materials

Aspergillus

Fungi

Stachybotrys chartarum

sick building syndrome; severe hematologic and neurological damage

Viruses

tiny particles, smaller than bacteria and other pathogens, which must invade living cells in order to reproduce; when they invade, the cells are damaged or destroyed in the process releasing new particles to infect other cells

Lytic Viral Life Cycle

The Lytic life cycle results in the destruction of the infected cell-

The viral DNA exists as a separate free floating molecule within the infected cell- Some viruses actively burst the cell so progeny virions can depart

Lysogenic Viral Life Cycle

the integration of viral DNA into the host genome:- After integration, viruses become "quiet" and reside in the host cells for long periods of time without actively replicating- Because the viral DNA is integrated into the host DNA, each time the host cell replicates, the viral DNA is replicated too

Eventually, an environmental trigger of some sort can reactivate them, and they can start making virus particles again

the main purpose of a virus is to

hijack the cell to make progeny

Retroviruses

An RNA virus that reproduces by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer-causing viruses.

Oncoviruses

viruses that cause cancer

The viral genome integrates into the host genome and disrupts important cell cycle control mechanisms

The virus requires actively dividing cells to replicate, and pushes the host cell into the cell cycle repeatedly through a virulence factor

Oncolytic viruses

viruses that infect and kill cancer cells

The oncolytic virus can infect cancer cells, and can replicate in these cells due to the presence of the aberrant protein

The virus lyses the cancer cell at the end of the viral life cycle