Lecture 4: Disease and Epidemiology Flashcards
What is pathology?
Study of disease
What does aetiology mean?
The cause of disease
Pathogenesis
development of disease
Infection
invasion or colonization of the body by pathogens
Define disease
an abnormal state in which the body is not performing normal functions, example: E. coli- present in healthy intestine, but pathogenic in UTI
What is the difference between normal microbiota and pathogenic?
Microbiota are specifically adapted for different systems. What may be normal and healthy in one system can become pathogenic if it enters a different system.
Human Microbiome Project
analyzes relationships between microbial communities on the body and human health
Transient microbiota
may be present for days, weeks or months and then disappear
Normal microbiota or normal flora…
permanently colonize the host and do not cause disease under normal conditions
Normal microbiota make colonies in certain region of body
Distribution and composition of normal microbiota are determined by what factors?
- Nutrients
- Physical and chemical factors
- Host defences
- Mechanical factors
What is microbial antagonism?
Also known as competitive exclusion, this is competition between microbes such that normal microbiota protect the host.
How do normal microbiota antagonize other microbiota?
- Compete for nutrients
- Produce substances that are harmful to invading microbes
- Affect pH and available oxygen
Give an example of microbial antagonism.
E.coli inhibit the growth of Salmonella and Shigella
Commensalism
one organism benefits and the other is unaffected. Eg. S epidermis inhabit the skin
Mutualism
both organisms benefit eg. E. coli synthesizes vitamin K
Parasitism
one organism benefits at the expense of the other. Many disease causing bacteria are parasitic.
Symbiosis
the relationship between normal microbiota and the host, one organism is dependent on the other.
Some normal microbiota are _______ ________
opportunistic pathogens
The same pathogen must be present in every case of the disease.
Koch’s first postulate
Koch’s second postulate
The pathogen must be isolated from the diseased host and grown in pure culture.
Pathogen from the pure culture must cause the same disease when inoculated into a healthy, susceptible lab animal.
Koch’s third postulate
Koch’s 4th postulate
The pathogen must be isolated from the inoculated animal and must be shown to be the original organism.
What are the three exceptions to Koch’s postulate?
- Some pathogens can cause several disease conditions
- Some pathogens cause diseases only in humans
- Some microbes have never been cultured.
What are infectious diseases?
Disorders caused by a microorganism which can be passed from person to person.