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Infection A > Session 6 Lecture 1 > Flashcards

Session 6 Lecture 1 Flashcards

1
Q

What shape is streptococci?

A

Gram positive cocci

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2
Q

What are the different ways you can classify streptococci based on haemolysis?

A
  • alpha haemolysis
  • beta haemolysis
  • non-haemolytic gamma
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3
Q

What is the action of alpha haemolysis on a blood agar?

A

Partial breakdown

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4
Q

What is the action of beta haemolysis streptococci on a blood agar?

A

Complete break down of the red blood cells

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5
Q

What is the action of non-haemolytic gamma streptococci on a blood agar?

A

No red blood cells are destroyed

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6
Q

Give an example of beta haemolytic streptococci?

A

Streptococci pyogenes

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7
Q

Give an example of an alpha haemolytic streptococci?

A

Streptococcus pneumoniae

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8
Q

Give an example of a non-haemolytic gamma streptococci?

A

Enterococcus faecalis

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9
Q

What is another name for alpha haemolytic streptococci?

A

Viridans’ streptococci

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10
Q

Define pyogenic

A

Pus producing

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11
Q

Classify streptococcus pyogenes?

A

Lancefield group A beta haemolytic streptococcus

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12
Q

How can you divide the streptococcus pyogenes virulence factors into groups?

A

Somatic virulence factors and exotoxic virulence factors

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13
Q

What are somatic virulence factors?

A

Stuck to the cell (integral part of the organism)

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14
Q

What are exotoxic virulence factors?

A

Released from the cell

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15
Q

Name some streptococcus pyogenes virulence factors?

A

Hylauronic acid capsule, M protein, Adhesin, Streptolysins, DNAases

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16
Q

How does hylauronic acid perform as a virulence factor?

A

Inhibits phagocytosis and poor immunogen because of its similarity to human connective tissue

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17
Q

How does M protein act as a virulence factor?

A

Resistance to phagocytosis by inhibiting activation of alternative complement pathway on bacterial cell surface.

18
Q

How does adhesin work as a virulence factor?

A

Adhesion is the first step in colonisation/infection

19
Q

What causes streptococcal pharyngitis?

A

Streptococcus pyogenes

20
Q

Between which ages is streptococcal pharyngitis most common?

A

5-15 years

21
Q

How is streptococcal pharyngitis spread?

A

Droplet spread therefore association with overcrowding

22
Q

What are the clinical features of streptococcal pharyngitis?

A

Abrupt onset sore throat, malaise, fever, headache , lymphoid hyperplasia, tonsilopharangeal exudates

23
Q

What would a a throat swab of someone with strep pharyngitis show?

A

Group A strep

24
Q

What are the complications of streptococcal pharyngitis?

A

Scarlet fever, suppurative complications, acute rheumatic fever

25
Q

How does scarlet fever arise from streptococcal pharyngitis?

A

Due to infection with streptococcal pyrogens exotoxin strain of s.pyogenes

26
Q

What are some clinical features of scarlet fever?

A

High fever, sepsis, arthritis and jaundice

27
Q

How might suppurative complications arise from streptococcal pharyngitis?

A

Pus breaks off from tonsil and travels to the sternum

28
Q

Give examples of suppurative complications?

A

Peritonsillar cellulitis/abscess, retropharyngeal abscess, mastoiditis, sinusitis, otitis media and meningitis

29
Q

What is acute rheumatic fever?

A

Inflammation of heart, joints and CNS.

30
Q

Give examples of streptococcus pyogenes skin infections?

A

Impetigo and erysipelas

31
Q

Who is affected by impetigo?

A

Childhood infection 2-5 years

32
Q

How does impetigo present?

A

Initial skin colonisation, followed by intradermal innoculation

33
Q

Impetigo is the most common cause of…

A

Glomeruonephritis

34
Q

What is erysipelas?

A

Dermis infection with lymphatic involvement

35
Q

What areas of the body does erysipelas affect?

A

Face and lower limbs

36
Q

What other skin infections can be caused by streptococcus pyogenes?

A

Cellulitis and necrotising fasciitis

37
Q

What is cellulitis?

A

Skin and subcutaneous tissue infection

38
Q

What is necrotising fasciitis?

A

Infection of deeper subcutaneous tissues and fascia

Rapid, extensive necrosis

39
Q

What causes streptococcal toxic shock syndrome?

A

Deep tissue infection with strep pyogenes and bacteraemia and vascular collapse and organ failure

40
Q

What is the prognosis of someone with streptococcal toxic shock syndrome?

A

From health to death in hours

Infection A (18 decks)

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