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302 infection and immunity > bacterial pathogenesis and infectious disease > Flashcards

bacterial pathogenesis and infectious disease Flashcards

1
Q

what are the different shapes of bacteria?

A
  • cocci- round
  • bacilli- rods
  • spirals
  • vibrio
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2
Q

what do gram positive bacteria stain?

A

purple

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3
Q

what do gram negative bacteria stain?

A

pink

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4
Q

what is the cell wall of gram positive bacteria like?

A
  • thick peptidoglycan layer

- lipoteichoic and teichoic acid layer

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5
Q

what is the cell wall of gram negative bacteria like?

A
  • thin peptidoglycan layer
  • outer and inner membrane
  • lipopolysacharides (lps)
  • proteins ad pores
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6
Q

What is an example of an obligate aerobe?

A

clostridium

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7
Q

what is an example of an anaerobe?

A

s.aureus

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8
Q

what are the different types of haemolytic streptococci?

A
  • α haemolytic ‘viridans’ streptococci
    These cause partial haemolysis of blood agar and a greenish colour
  • β haemolytic streptococci
    These cause complete haemolysis making the blood agar translucent
  • γ (non)- haemolytic streptococci
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9
Q

what are the different things that confer virulence of the s.aureus infection?

A

Coagulase
Stimulates clotting
Role in immune evasion
Not expressed by less virulent ‘coagulase negative’ staphs

Adhesins: bind host proteins
- elastin binding protein, collagen protein, fibronectin binding protein

cytotoxins- including cytotoxins, exfoliative toxins and super antigens

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10
Q

what is an example of a facultative anaerobe?

A

e.coli

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11
Q

what are the 4 different ways of describing bacteria?

A
  1. staining
  2. growth- aerobes vs anaerobes
  3. morphology
    - microscopic
    - macroscopic- on agar
  4. typing
    - related species
    primary serology
    - correlating genotypes
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12
Q

what is a commensal bacteria?

A
  • bacteria which is probably not causing disease when taken from a clinical sample
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13
Q

what is a pathogen?

A
  • a bacteria that is probably causing disease when identified from a clinical sample
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14
Q

what are the 3 things that make bacteria pathogenic rather than commensal?

A
  1. The immune status of the patient.
  2. The site / sample in question.
  3. The disease causing properties of the bacteria (virulence).
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15
Q

what type of bacteria are streptococcus pyogenes and streptococcus aureus?

A

gram positive cocci

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16
Q

what type of bacteria is e.coli?

A

gram negative rods

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17
Q

when are surface proteins most responsible for virulence in s.aureus?

A

the exponential phase

18
Q

when are secreted proteins most responsible for virulence in s.aureus?

A

the stationary phase

- secreted proteins include toxins

19
Q

what does protein A do in s.aureus?

A
  • binds the FC portion of IGg

- involved in immune cloaking

20
Q

what are the actions of adhesin in s.aures?

A
  • tussle addrehence
  • for colonisation
  • allows deeper infections
  • allows immune evasion by cloaking
21
Q

what are the 4 main types of staphylococcal toxin and what are they involved in?

A
  1. cytotoxin
    - PVL lyses polymorphs and has a role in MRSA
  2. exfoliative toxins
    - proteases
    - target epidermal structural proteins
  3. exotoxins
    - superantigens
    - cause massive Tcell response in toxic shock syndrome
  4. enterotoxin
    - ingestion leads to vomiting and diarrhoea
22
Q

what is ritter’s syndrome?

A
  • caused by exfoliative toxin
  • serine proteases specific fro desmoglein 1
  • causes sheet-like desquamation
23
Q

what are the different ways that s. aureus infections can manifest?

A
  • normal comensal
  • soft tissue infection
  • vascular line related infection
  • bacteremia
  • surgical site infections
  • toxin mediated infections
24
Q

what are some s.aureus bacteraemia?

A
  • endocarditis
  • osteomyelitis
  • septic arthritis
25
Q

what type of bacteria is s.epidermsis?

A
  • coagulase negative gram poitive staph

- found normally on skin surface

26
Q

what things can s.epidermis cause when it becomes pathogenic?

A
  • Central venous line infection
  • Endocarditis (prosthetic valve)
  • Orthopaedic surgical infections
  • Foreign material in a ‘sterile’ place
    grafts, implants etc
27
Q

where do streptococci colonise?

A

a huge family of Gram positive bacteria which colonise the GI tract and skin

28
Q

what are the 3 ways to classify streptococci?

A
  1. Appearance on blood agar (haemolysis)
    e. g ‘beta haemolytic strep’
  2. Lancefield groups (A, B, C etc)
    Surface carbohydrate antigens
    e.g. ‘group A strep’
  3. True species names (S. pyogenes, S. pneumoniae etc) e.g.
29
Q

how is s.pyogenis classified?

A

S. pyogenes = group A strep and is a beta haemolytic strep

30
Q

what are superficial infections caused by strep. pyogenes?

A

Pharyngitis

Cellulitis

31
Q

what are deep infections caused by s.pyoges?

A
  • myositis

- necrotising faciatis

32
Q

what are 2 common autoimmune sequelae of s.pyogenes?

A

Rheumatic fever – a major cause of heart disease

glomerulonephritis

33
Q

what are the virulence factors in s.pyogenes?

A

M PROTEIN

  • Fibronectin binding protein
  • collagen binding protein
  • c5a peptidase
34
Q

how is streptococcal M protein involved in pathogenesis of S.pyogenes?

A
  1. Binds serum factor H – regulator of complement activation
    - Prevents opsonisation

2.Has an alpha-helical ‘coiled-coil’ protein
Molecular mimickry

35
Q

how can molecular mimicry lead to post strep heart disease?

A
  • M protein is a a helical coiled coil structure
  • has homology to cardiac myosin and tropomyosin
  • recurrent childhood infection can cause cross reactive anti self response which damages the heart

occurs after rheumatic fever

36
Q

how can molecular mimicry lead to post strep glomerular nephritis?

A
  • M protein has alpha helical coiled coil structure
  • which has homology with glomerular basement membrane
  • after recurrent childhood infection a cross reactive anti self response can occur
37
Q

what type of bacteria are enterococcus?

A

gram positive coccus

38
Q

what are examples of gram negative rods?

A

Klebsiella
Enterobacter
Citrobacter

39
Q

what can occur when opportunistic infections gain access to sterile sites?

A
  • wound infections

- HAP

40
Q

what are 3 main diseases caused by E.coli?

A

UTI
Enteric
Meningitis (Neonatal, elderly, immunocompromised)

41
Q

what are 4 main virulence mechanisms of e.coli?

A
  1. adhesins
    - p. fimbria= pyelonephritis associated
    - non fimrial= GI Adhesin causing diarrhoea
  2. sidephores
    - enterobactin
    - powerful iron chelators
    - essential for survival in tissues
  3. capsule
    - protects against complement
    - K1 serotype allows crossing the BBB to cause meningitis in neonates
  4. toxins
    - enterotoxin- cause GI leak
    - verotoxin- disrupt ribosomal protein synthesis
42
Q

which pathogen is the biggest cause of urosepsis?

A

e. coli

302 infection and immunity (9 decks)

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