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Foundations Of Medicine PoD > Intro To Infection > Flashcards

Intro To Infection Flashcards

1
Q

What is a virus?

A
  • Unique, acellular, metabolically inert organism that only replicate within living cells
  • unclassified type of cell
  • 20-400 nm
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2
Q

What is bacteria

A

-chiefly round, spiral or rod shaped single called prokaryotic organism that typically lives in soil, water, organic matter or the bodies of plants and animals
- 0.2 to 0.5 um

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3
Q

What is fungi

A
  • Any kingdom of saprophytic and parasitic spore-producing eukaryotic typically filamentous organisms including moulds, yeasts and mushrooms
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4
Q

Micro-organisms that cause infection

A
  • Bacteria
  • viruses
  • fungi
  • parasites
  • prions
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5
Q

Common specimen types collected for culture

A
  • Mid stream specimen of urine ~ urinary tract infection
  • sputum ~ lower respiratory tract infection
  • throat swab ~ tonsillitis/pharyngitis
  • swabs ~ wound infection/ genital tract infection
  • faeces - infectious diarrhoea
  • blood culture ~ septicaemia
  • cerebrospinal fluid ~ meningitis
  • aspirate of pus ~ abscess
  • bone ~ osteomyelitis
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6
Q

Role of microscopy and culture in the diagnosis of bacterial infection

A
  • Unstained ~ to see while blood cells and parasites
  • GRAM stain ~ to visualise bacteria and yeasts/fungi
  • followed by bacterial culture and susceptibility testing
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7
Q

Difference between sterile and non sterile sites

A
  • Sterile sites (no commensal flora): brain, heart, liver, kidney
  • non sterile sites: mouth, oesophagus, lungs, stomach, intestine
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8
Q

Methods of detecting viruses

A
  • Molecular methods: real time / multiplex PCR
  • antigen detection
  • serology to determine immunity (using serum)
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9
Q

Diagnostic principles in parasitology

A
  • Microscopy of different life cycle stages
  • culture rarely possible
  • serology sometimes useful
  • importance of reference laboratories
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10
Q

Basic infection control measures

A

F ~ face coverings
A ~ avoid crowded places
C ~ clean hands regularly
T ~ two metre distance
S ~ self isolate

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11
Q

How can bacteria be identified?

A
  • Gram staining
    Positive - purple
    Negative - pink

Shape: cocci-spherical,
bacilli - rod shaped,
spiral-corkscrew

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12
Q

Structure and function in bacteria cells: chromosome

A
  • single chromosome
  • Contains genetic information
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13
Q

Cytoplasmic membrane

A
  • 5 -10 nm thick
  • made of phospholipids (40%) and proteins (60%)
  • allows passage of water and small uncharged molecules
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14
Q

Cell wall

A
  • 10-25 mm thick
  • made of peptidoglycan
  • thick, strong and relatively rigid-maintains shape
  • if cell wall is weekend or ruptured - osmosis means lysis will occur
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15
Q

Ribosome

A
  • Consider of RNA and associated proteins
  • synthesise proteins
  • divided into subunits
  • Bacteria have a 70s ribosomes with large (50s) and small (30s) subunits
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16
Q

Peptidoglycan

A

~ N-acetylglucosamine acid and n-acetylmuramic acid molecules linked alternately in a chain, with short peptides forming cross-links

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17
Q

Lipopolysaccharide outer membrane

A
  • Only in gram negative bacteria
  • protects peptidoglycan from bile salts and lysozyme
  • blocks antibiotics from getting into cue
  • lipid A may give rise to endotoxic shock when released into bloodstream
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18
Q

Capsule

A
  • polysaccharide wall outside bacteria
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19
Q

Flagella

A
  • Long filament twisted spirally
  • gives bacterial ell mobility
    A… (1)
    B.. (one point)
    C… (both sides)
    D… (all over)
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20
Q

Fimbriae

A
  • Gives adherence
  • between bacterial cus and host cells
  • numerous but shorter than flagella
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21
Q

Plasmid

A
  • Contain genetic info
  • genetic variation through transfer of plasmids or spontaneous mutation
22
Q

Bacteriophage

A
  • Virus that infects bacteria
  • destroys host cells
  • burst out by lysis
23
Q

Spores

A
24
Q

Classification and nomenclature used for bacterial species

A

Classification:
phenotypic (gram stain, growth requirements, serologic, mass spectrometry)

Genotype cribosomai raw sequence analysis, whole genome sequencing)

Nomenclature:
Genus + species

25
Q

Difference between gram negative and gram positive bacteria

A

Gram positive:
plasma membrane (contains proteins)
pepticloglycan

Gram negative:
plasma membrane contains proteins)
Periplasmic space
Peptidoglycan
Periplasmic space
Outer membrane (contains proteins + LPS)

26
Q

How bacteria replicate and create genetic variation

A

Conjugation:
1. F pillus On F + attaches to receptor of F minus
2. Combine and endonuclease goes to origin on transfer on plasmid
3. A strand of plasmid moves to F minus celI
4. Complimentary strand is synthesised
5. Eventually all cells become A plus

27
Q

Detection and culture of bacteria

A
  • Individual Bactria can only be seen using microscope
  • colonies can be cultured on solid medium (agar)
28
Q
  • Basic classification and characterisation of viruses
A
  • Small 20 -400 mm
  • non cellular (cannot replicate independently)
  • icosaheddral: 20 faces
  • helical
  • complex
29
Q

Principles of viral culture

A
30
Q

Examples of human virus infections of major importance

A
  • EBV
  • Human herpes
  • Human T-cell lymphotropic virus
  • hpv
  • hepatitis B and C
31
Q

Structure of viruses

A
  • nucleic Acid
  • Vision associated polymerase
  • protein capsid
  • lipid envelope
  • spike projections
32
Q

How viruses replicate

A

Find video

33
Q

Concept of host range in relation to viruses

A
  • Some viruses only infect humans eg. Smallpox, measles
  • some may also infect other animals/birds:
    ~ transmission of novel virus to humans
    ~ confection of human and animal or bird strains in one organism may lead to recombination and
    Generation of new strain
34
Q

Consequences of viral infection

A
  • Clearance of virus
  • chronic infection
  • latent infection
  • transformation
35
Q

Concept of viral latency

A
  • Following primary infection, some viruses lie dormant in the cell

-The full viral genome is retained in the host cell, but its expression is restricted, such that few viral antigen and no viral particles are produced

  • reactivation of viral replication can occur
  • reactivations may or may not cause apparent disease
  • reactivation more likely to occur and more severe in immunocompromised
36
Q

Link between viruses and cancer + mechanism through which this results

A
  • A number of viral infections can lead to cancer

Mechanism:
- modulation of cell cycle (driving cell proliferation)
- modulation of apoptosis (prevention)
-Reactive oxygen species mediated damage (some persistent viral infections can cause persistent inflammatory processes which lead to cancer via reactive oxygen species)

37
Q

Indications for and principles of anti-viral therapy

A
  • Only used in a minority of viral infections
  • can be used for: prophylaxis (to prevent infection), pre-emptive therapy (evidence of infections replication detected, befor symptoms are apparent)
  • overt disease
  • suppressive therapy (keep below rate that can cause tissue damage in asymptomatic patient)
38
Q

How to prevent viruses

A
  • Immunisation
  • prophylactic treatment post exposure
  • facts
  • blood / tissue, organ screening
  • antenatal screening
39
Q
  • What is meant by the term vaccination
A
  • Administration of antigenic material to stimulate un individuals immune system to develop adaptive immunity to a pathogen
40
Q

Types of vaccines available for active immunisation

A
41
Q

Contra-indications to vaccination

A
  • Temporary: febrile illness, pregnancy
  • permanent: allergy, immunocompromised
42
Q

How immune response occurs

A
43
Q

Concept of herd immunity

A
  • Vaccinated individuals being less likely to be a source of infection to others
  • reduces risk of unvaccinated being exposed
44
Q

Vaccination schedules for children

A

See goodnotes

45
Q

Vaccines that may need to be given to travellers

A
  • Hepatitis A
    Typhoid
    Neisseria meningitidis
    Cholera
    Yellow fever
    Japanese encephalitis
    Tick-borne encephalitis
    Rabies
46
Q

Main groups of parasites

A

Protozoa
Helminths (worms)
Ectoparasites

47
Q

Diseases caused by enteric and blood-borne parasites

A

Malaria

48
Q

Diagnostic principles of parasitology

A
49
Q

What is a parasite?

A
  • Organism that lives in or on a host and derives its nutrients at expense of this host
50
Q

Protozoa

A
  • Malaria, amoebae, flagellates
  • microscopic, single-celled organisms
  • can be free-living or parasitic in nature
  • able to multiply in humans
  • transmission
51
Q

Helminths

A
  • Roundworms, tapeworms, flukes
  • nematode (roundworm) eggs hatch in intestinesoften asymptomatic, mass can obstruct bile duct or small intestine,
  • Cestodes (tapeworms) larval cysts ingested,
    Adult tapeworms in human,
  • trematodes (flukes/flatworms) schistosomiasis, contact with freshwater where snail intermediary host present
52
Q

Ectoparasite’s

A
  • Live outside body

Foundations Of Medicine PoD (5 decks)

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