Bacteria and disease Flashcards
Do are humans colonised with microorganisms?
From birth
Are microorganisms considered to be benign or malignant?
Benign
Why are microorganism considered benign?
Few contribute to health and fewer pose direct threats to health
What do microorganism normally associate with in humans?
Human body tissue
Do most microorganism cause diseases?
No
What are the few diseases caused by microorganisms?
- Viruses (Influenze, Lassa fever, AIDS)
- Bacteria (Diptheria, TB, anthrax)
- Fungi (Candidiasis)
- Protozoa (Malaria, sleeping sickness)
Define microbial pathogenicity:
The biochemical mechanisms whereby microorganisms cause diseases
Do have an equal or unequal probability of causing infections and disease?
Unequal
Define infection:
Successful persistence or multiplication of a pathogen on or within the host
Define disease:
An interaction which causes significant overt damage to the host
Define pathogenicity:
The way in which a microorganisms causes disease
Define virulence:
Relative term e.g. one pathogen vs another
Do different microorganisms have the same or different pathogenic potentials (virulence)?
Different
What are examples of low virulence?
Common cold, salmonella food poisoning, candidiasis, Pneumocystis crania pneumonia
What are examples of high virulence?
Malaria, anthrax, plague and Lassa fever
What factors affect the severity of a microorganism disease?
- Host
- Immunological status
- Physiological status
- Genetic makeup
- Route of infection (inhalation, skin, ingestion)
- Dose (high, low)
What can an infectious dose/lethal dose graph measure?
Virulence
How do you find the virulence from an infectious dose/lethal dose graph?
Look at quantity when 50% infected
On an infectious dose/lethal dose graph does a lose dose mean in terms of virulence?
High virulence
What is the infectious dose of Bacillus anthracis?
10,000
What is the infectious dose of Vibrio cholerae?
10^6
What is the infectious dose of Salmonella enterica?
10^9
What is the infectious dose of Campylobacter jejuni?
800
What is the infectious dose of Francisella tularensis?
10
What is the infectious dose of Mycobacterium tuberculosis?
50
What is the route of infection of Mycobacterium tuberculosis?
Inhalation
What is the route of infection of Francisella tularensis?
Insect bite
What is the route of infection of Campylobacter jejuni?
Ingested in food
What is the route of infection of Salmonella enterica?
Ingested in food
What is the route of infection of Vibrio cholerae?
Ingested in water
What is the route of infection of Bacillus anthracis?
Inhalation
How does a pathogen need to do in order to cause a disease?
- Colonise host tissues
- Grow within host tissue
- Avoid host defence mechanisms
- Cause damage to the host
How do pathogens damage the host?
Via 2 principal mechanisms
- Produce effectors which damage host tissue
- Evoke profound immune responses which cause damage
What are exotoxins?
Toxins as effectors
What do neurotoxins cause?
Paralysis
What do enterotoxins cause?
Sickness and diarrhoea
What do cytotoxins cause?
Cell death