What are 3 ways in which infectious microorganisms are transmitted?
- direct contact
- indirectly by vectors (insects) = bites, stings, passive transfer
- direct exposure = faecal oral transmission through food/water or soil
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What is the primary means of respiratory tract infections?
aerosolised microorganisms in droplets
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What are the 4 stages of the clinical infectious disease process, from the viewpoint of the infect individual?
1. Incubation period
2. prodromal stage
3. invasion period
4. convalescence
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What is the incubation period?
the interval between exposure to an infectious agent and the appearance of the first symptoms
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What happens in the prodromal stage?
the appearance of initial symptoms when are often mild
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What is the invasion period?
the pathogen multiples rapidly, invading further, affecting tissues at the site of initial colonisation and other areas
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What is the convalescence period?
the general removal of infectious agent from the body, symptoms decline
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What is pyrexia?
a fever - a rise in body temperature above normal
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What are pyrogens?
a circulating protein agent that produces a fever, causing a rise in body temperature
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What are exogenous pyrogens?
derived from OUTSIDE the host
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What are endogenous pyrogens?
produced by the individual
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What are the 4 classes on infectious microorganisms?
- prokaryotic (no enclosed nucleus)
- no mitochondria
- no membrane bound organelles
- reproduce asexually by simple cell division
- live in soil, water or air
- live as parasites of humans, animals and plants
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What are exotoxins?
proteins released during bacterial growth, a poisonous substance
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When are endotoxins (LPS) released?
during lysis (destruction) of the bacteria
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What bacteria produces endotoxins and what does this do?
Pyrogenic bacteria
it activates inflammatory response and produces a fever
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What is bacteremia?
bacteria being transported in the blood due to failure of body's defence mechanisms to infect other organs or multiply in the blood (sepsis)
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What is a virus?
minute particle that is capable of replication but only within living cells
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What is a simple microorganism?
does not possess metabolic organelles
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What is a viron?
basic viral structure = nucleic acid protected by protein shell called the capsid
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What is fungus?
a simple microorganism that lacks the green pigment called chlorophyll
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What is an infection with a fungus called?
mycosis
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What is fungi that invades the skin, hair or nails?
dermatophytes
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What is a parasite?
any living thing that lives in or on another living organism
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What is a protozoa?
a single-celled parasitic organism
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Name 3 countermeasures against pathogens
1. infection control measures
2. antimicrobials
3. active immunisation: vaccines
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