ToB: Infectious Diseases Flashcards
What is the purpose of Koch’s Postulates and what are they?
Criteria to identify the causative agent of a disease:
- The same pathogen must appear in every case of disease
- Pathogen must be able to grow in pure culture
- Pathogen must be isolated in pure culture and cause same symptoms as expected
- If the pathogen is taken out of an inoculated organism it should be the same pathogen
Name 4 exceptions to Koch’s Postulates
- some pathogens can’t be grown in pure culture
- some pathogens cause multiple diseases
- some diseases cause multiple pathogens
- some diseases only cause diseases in humans
Which myeloid cell directly combats macro parasites?
Eosinophils
What are the 3 ways infectious diseases are classified?
- Clinically: based on signs and symptoms
- Epidemiologically: based on the reservoir
- Microbiologically: identifying the causative agent
Name 3 macroparasites
platyhelminths, nematodes and arthropods
Why are prions hard to detect/eliminate?
Which disease is associated with prions?
They are heat, radiation and disinfectant resistant.
Hard to detect: They are slow replicating and have a long incubation period, and therefore lie dormant for a long time and when you’re infected you don’t elicit an immediate immune response
Creutz-Jacob disease: prions trigger proteins in the brain to fold abnormally
Name the 5 steps of the lytic viral cycle
- attachment
- penetration
- synthesis of viral nucleic acids and proteins
- packaging and assembly
- release and cell lysis
What is the Baltimore classification for?
Classifying viruses based on genome, envelope, shape, etc.
Name two methods to identify bacteria and which diseases can be identified with the “less common” method
Acid-fast stain: cheaper but more insensitive, can be used for mycobacteria in leprosy
Gram Staining:
Identify the structural differences in (+) and (-) gram cell walls of bacteria
Gram (+) cell walls: Have a much thicker peptidoglycan layer
Gram (-) cell walls: have a lipopolysaccharide layer that protects against the immune system and chemotherapeutic agents
Name the 3 steps in gram staining
- Add crystal violet stain which binds to the peptidoglycan layer of (+) and (-) bacteria
- Add alcohol which washes away the stain, the (-) peptidoglycan layer is so thin it should wash away and appear clear, the (+) bacteria should still be purple
- Pink Counterstain: (-) is now blue, and (+) is now pink
What makes the microbiome opportunistic?
Our microflora/gut bacteria begin unharmful but have the potential to become harmful following a mutation, microbiome differences are linked to individual health issues
Which bacterial structure looks like chains and which structures can they form?
Streptococci can form external structures such as flagella, pilli, cell envelopes and capsules
Which bacterial structure looks like rods and which structures can they form?
Bacilli can form internal structures like spores and inclusion granules
Explain the relationship in pathogen-host in commensalism in comparison to mutualism
Commensalism is when the pathogen benefits with no harm to the host
Mutualism is when both benefit
When are fungi infections more severe, how are they normally caused and name 2 common conditions
What characteristic of fungi protects them?
More severe if you’re already immunocompromised, normally caused by external environment or normal gut bacteria: athlete’s foot and ringworm
Thick chitin cell wall
What are protozoa? How are they commonly contracted and name an example condition.
Name 3 pathogenic protozoa
Parasitic or free-living microparasites, mostly contractable through food or water: malaria
Sporozoa, flagellates and amoebas
How do arthropods cause disease?
Directly by feeding and indirectly by transmitting
Name 8 ways parasites can be transmitted
Air-borne, sexually, food and water, vector-borne, inoculation, orally, skin, trans-placental
What is it meant by pathogenicity?
The propensity of an agent to cause disease/clinical symptoms
What is the incubation period?
Period of time between exposure and onset of clinical symptoms/signs
What is it meant by an inapparent/subclinical infection
An infection with no clinical signs/symptoms
What is a bacteriophage and how does it reproduce?
A bacteriophage is a virus that infects bacteria. It uses the lysogenic cycle to replicate prophage (viral genetic info)
Compare and contrast cellular content, DNA and replication differences in prokaryotes and eukaryotes
Prokaryotes are missing a distinct nucleus,
DNA is usually in a nucleoid but can have additional plasmids, transcription and translation can be carried out simultaneously
Eukaryotes have a distinct nucleus bound by a nuclear membrane, DNA is on several chromosomes, transcription and translation are separate, and they have membrane-bound organelles
What ‘stage’ comes before and leads to infection?
Colonization/carriage transient phase: pathogen is inside body but no clinical signs/symptoms
