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Infection Term 4 > Infection Intro- 1.1. & 1.2 > Flashcards

Infection Intro- 1.1. & 1.2 Flashcards

1
Q

What does the germ theory state?

A

Microorganisms are the cause of many diseases

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2
Q

What are the 7 types of microorganisms? ( BAPAFV)

A 
Bacteria 
Archaea
Protozoa
Algae 
Fungi 
Viruses 
- Multicellular animal parasites eg helminths
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3
Q

State Koch’s Postulates (4)

A

1) Microorganism must be observed in every case of the disease
2) Microorganism must be isolated and grown in pure culture
3) Pure culture, when inoculated in animals must reproduce the disease.
4) Microorganism must be recovered from the diseased animal.

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4
Q

What does phylogeny state? (BAE)

A

Bacteria, Archaea and Eucarya all come from the same universal ancestor

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5
Q

How do we classify organisms?

8

A

Determined Kind People Can Often Find Ghastly Screams

Domain 
Kingdom
Phylum
Class 
Order
Family 
Genus 
Species
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6
Q

What classification is used for viruses and how do you classify them?

A

BALTIMORE CLASSIFICATION

Classes 1-7

  • Classes 1 and 2 MUST replicate in the nucleus only
  • Classes 3 to 7 must replicate in the cytoplasm
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7
Q

Name the 5 shapes of bacteria

A

1) Spheres - cocci
2) Rods-bacilli
3) Spirals- spirilla
4) Comma- vibrios
5) Corkscrews- spirochetes

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8
Q

List differences between gram positive and gram negative bacteria

A
  • Gram positive bacteria have a peptidoglycan cell wall and stains PURPLE with gram
    -Gram negative bacteria has a cell wall with a thin layer of peptidoglycan and an
    OUTER MEMBRANE with a lipopolysaccharide
    it stains RED/PINK with gram
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9
Q

How do bacteria reproduce?

A

by BINARY FISSION

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10
Q

Describe Binary Fission

A
  • an organism duplicates its DNA and divides by cytokinesis

- this produces two identical daughter cells

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11
Q

What is the purpose of endospores for bacteria?

A

Help bacteria survive in hostile environments by allowing them to be encapsulated and desicated in them
-they are dormant structures and are resistant to physical and chemical conditions

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12
Q

Define infection

A

Growth of microorganism in a host, not synonymous with disease

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13
Q

Define a pathogen

A

An organism that causes damage to a host

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14
Q

Types of pathogens (3) (POZ)

A

Primary
Opportunistic
Zoonotic ( E.Coli)

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15
Q

Define Pathogenicity

A

ability of a microorganism to cause disease

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16
Q

Define Virulence

A

the degree of pathogenicity

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17
Q

Define Parasite

A

an organism that lives on or in a secondary organism called a host

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18
Q

How do opportunistic pathogens work?

A

they have the potential to cause disease with the right conditions

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19
Q

How do viruses replicate?

A

-the virus particle attaches to the host cell before penetrating it.
-uses the host cell’s machinery to replicate its own genetic material.
-after replication, the virus particles leave the host, by either:
budding
lysis; bursting out of the cell

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20
Q

Describe virus replication

A
  • viruses replicate by budding
  • newly formed viral particle pushes against the host cell’s plasma membrane, a portion adheres to it.
  • the virus is released from the cell by LYSIS
  • after escaping from the host cell, the virus can enter a new cell and multiply
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21
Q

Define virulence

A

A pathogen’s ability to infect or damage a host

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22
Q

What do virulence and pathogenicity depend on?

A

the composition of the genome

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23
Q

What is attenuation?

A

when a pathogen’s virulence is reduced eg in cultured conditions like VACCINES ( For small dose exposure)

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24
Q

What is ID5O?

A

Estimated number of organisms/ virus particles required to produce infection in 50% of normal adult humans exposed by a given route

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25
Q

Name the 3 functions of virulence factors

IEC

A

allow pathogen to:

1) Invade the host
2) Evade host defences
3) Cause disease

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26
Q

List the 5 functions of virulence factors

ACITI

A

1) Attachment- via adhesions
2) Colonisation- and enzymes
3) Invasiveness
4) Toxins-and enzymes
5) Inhibition of Phagocytosis

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27
Q

Define a toxin

A

Substances that contribute to pathogenicity

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28
Q

Define pathogenicity

A

ability to produce a toxin

29
Q

Define toxaemia

A

presence of a toxin in the host’s blood

30
Q

Define toxoid

A

Inactivated toxin used in a vaccine

31
Q

Define antitoxin

A

antibodies against a specific toxin

32
Q

What are the two types of toxins?

A

Exotoxin- produced and secreted by bacteria

Endotoxin- within bacterial composition

33
Q

Describe endotoxins

A
  • gram negative bacteria
  • found in outer layer of gram negative bacteria ie lipid portion
  • Lipid A polysaccharide; highly antigenic and promotes a strong immune response
34
Q

What is the endotoxin’s mode of infection?

A

Upon digestion by microsome, the endotoxin’s lipid fragments are expelled from the phagocyte
-this induces inflammation, fever, endotoxic shock, diarrhoea and blood coagulation

35
Q

What type of bacteria releases exotoxins?

A

both gram positive and gram negative bacteria

ALL MAJOR GRAM POSITIVES PRODUCE EXOTOXIN

36
Q

What are the three types of exotoxins? ( based on mode of action)

A

Class I: disrupt pattern of communication of signalling at host cell membranes

Class II: cause physical damage to cell membranes

Class III: enter target cells and directly alter function

37
Q

What are the three classes of toxins? (NES)

A
  • Neurotoxins
  • Enterotoxins
  • Superantigens
38
Q

Give two examples of neurotoxins

A

tetanus

botulinum

39
Q

Give two examples of enterotoxins

A

staph aureus

cholera

40
Q

What are enterotoxins?

A

exotoxins that act in the small intestine; cause a massive secretion of fluid into intestinal lumen

41
Q

Give two examples of superantigens

A

TSST

Staphylococcal scalded skin syndrome

42
Q

Describe superantigens

A
  • Type 1 exotoxin ie disrupt pattern of communication within cells
  • cause an intense immune response due to release of cytokines from host cells

eg TSST

43
Q

What symptoms are caused by superantigens?

A
  • fever
  • nausea
  • vomiting
  • diarrhoea
  • shock
  • death
44
Q

Describe the interaction between superantigens and T cells

A

superantigen loses specificity and is bound to T cell irrespective of recognition
-very heightened, multiple response to a generic stimulus

45
Q

Describe TSST

and name three symptoms (HOD)

A

Toxic Shock Syndrome Toxin

TSST-1 (TYPE 1 ENDOTOXIN)

-Superantigen
causes hypotension, desquamative skin lesions and organ dysfunction

46
Q

Describe SSSS ( type 2; damage to membrane)

A 
Staphylococcal Scalded Skin Syndrome 
-exfoliation toxin 
causes bullae and skin exfoliation, 
fever
redness and lesions 
skin wrinkles and blisters
47
Q

How do type 2 toxins work? give an example

A

Membrane disrupting toxins

  • lyse host’s cells by making protein channels in the PM eg hemolysins, leukocidins
  • disrupting phospholipid bilayer

eg Clostridium- gas gangrene

-causes a change in supply of blood to an area
and increased permeability in membrane and

-increased blood flow and increased gas in tissue spaces

48
Q

Describe structure of clostridia

A
  • large
  • gram positive
  • bacilli (rods)
  • ANAEROBIC
  • spore forming
  • fermentative
49
Q

What is Vibrio Enterotoxin? eg needed

A

vibrio cholera ( cholera toxin)

A-B enterotoxin (1A 5B)

  • One of the B subunits binds to a glycoprotein receptor on membrane causing CLEAVAGE of unit
  • adenylyl cyclase converts ATP to cAMP
  • cAMP stimulates active secretion of electrolytes into intestinal lumen and water follows into intestine
50
Q

Name some symptoms of cholera and how do you treat it?

A

watery diarrhoea- rice stools
dehydration
thirst
metabolic acidosis because of loss of bicarbonate

Treat with ORT- Oral Replacement Therapy and then with antibiotics only if necessary

51
Q

Define Botulinum Toxin

A

caused by clostridium botulinum
A-B neurotoxin
3 types (food-borne, infant and wound)

METALLOPROTEASE toxin catalyses proteolysis of key proteins to block ACh release causing FLACCID PARALYSIS

52
Q

How can botulinum be harmful?

A

death from respiratory paralysis

53
Q

Mechanism of botulinum?

A

-toxin gets internalised into neuron by endocytosis and forms a toxin vesicle
-toxin’s light chain is released from vesicle into cytoplasm of nerve terminal
-light chain blocks ACh release by cleaving components of SNARE complex ( binding complex of ACh)
THEREFORE
ACh cannot bind to membrane so not released into synaptic cleft and to the post-synaptic membrane
ie no muscle contraction ie FLACCID PARALYSIS

54
Q

What is tetanus toxin?

A

clostridium tetani
A-B neurotoxin
-found as spores in soil or GI tract of animals, which develop into GRAM POSITIVE bacteria; that multiply and produce tetanospasmin

55
Q

What is the mechanism of tetanospasmin and what does it cause?

A

-binds to motor nerves, enters axons and travels to the body of the motor nerve in the spinal cord or brainstem via RETROGRADE INTERNEURON TRANSPORT

  • toxin migrates to synapse and binds to nerve terminals and stops release of neurotransmitters like GLYCINE and GAMMA-AMINOBUTYRIC ACID
  • causing increased chemical signals to motor nerves of muscles, causing continuous tightening and contractions and spasm
  • can travel via lymphatic system and bloodstream and have same effect elsewhere

causes SPASTIC PARALYSIS ( flexors and extensors continuously contract)

56
Q

Define microbiotica

A

community of microorganisms living in a specific environment

57
Q

Define microbiome

A

entire collection of genome elements of specific microbiotica

58
Q

What are the functions of the microbiome

A
  • maintaining intestinal integrity+supporting barrier function
  • breaking down food
  • providing essential nutrients, vitamins and short-chain fatty acids eg BUTYRATE
59
Q

What are the 4 dominant gut bacteria/phyla?

(FABP)

A

Firmicutes
Bacteroidetes
Actinobacteria
Proteobacteria

60
Q

What is vertical transmission?

A

acquisition of microbes directly from an organism’s parents

61
Q

What is horizontal transmission?

A

acquisition of microbes from sources other than direct parents eg environment or from non-parental conspecifics

62
Q

How does vertical transmission occur?

A

seeding via exposure to:

  • mother’s vaginal bacteria
  • mother’s gut bacteria
63
Q

What are the 4 ways vertical transmission happens via the vagina?

A

1) Onset of labour or rupture of membranes
2) GBS bacteria can travel up from vagina to amniotic fluid
3) GBS can also transfer as baby journeys down the birth canal
4) Aspiration into lungs

64
Q

How does vertical transmission occur in the mother’s gut?

A

exposed to GBS from contact with mother’s faecal matter during birth

65
Q

What is Group B Streptococcus?

A

belongs to PYOGENIC STREPTOCOCCI

  • STREP AGALACTIAE
  • gram positive
  • beta haemolytic bacteria

-common in GI and GU tracts
seen in pregnant women, infants, older adults

66
Q

What happens to newborns with GBS?

A
  • resp problems

- sepsis signs; large patches of red raw skin

67
Q

Name 3 obstetric risk factors for early onset GBS (PPI)

A

Preterm delivery
Prolonged rupture of membranes
Infection of placental tissues/amniotic fluid

68
Q

Name other risk factors for early onset GBS

A
  • GBS in mother’s urine during pregnancy
  • previous infant with GBS disease
  • low maternal levels of anti-GBS antibodies
  • African American
  • young maternal age
69
Q

What is dysbiosis?

A

persistent imbalance of gut’s microbial community relates to many diseases (alteration of gut microbiotica composition)

eg IBD
IBS
Celiac disease
Colorectal cancer

Infection Term 4 (8 decks)

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