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ELM2 - infection & immunity > lecture 3 - pyogenic gram-positive cocci > Flashcards

lecture 3 - pyogenic gram-positive cocci Flashcards

1
Q

What is the full name of staph. a?

A

Staphylococcus aureus

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2
Q

What is the full name of strep p.?

A

Streptococcus pyogenes

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3
Q

What are the 2 bacteria that most commonly cause skin and soft tissue infections?

A

Staphylococcus aureus & streptococcus pyogenes

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4
Q

What classfication of bacteria are staph. aureus and strep. pyogenes?

A

pyogenic, gram-positive cocci

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5
Q

What does pyogenic mean?

A

Pus producing - purulent

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6
Q

What are the components of pus?

A

bacteria, neutrophils, fibrin

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7
Q

What is the inflammatory exudate in pyogenic gram-positive cocci infections?

A

Pus

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8
Q

What is an abscess?

A

Localised collection of pus in a fibrin-lined cavity

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9
Q

What is the arrangement of staph. aureus?

A

clusters

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10
Q

What is the arrangement of strep. pyogenes?

A

chains

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11
Q

Are strep and staph aerobic or anaerobic?

A

Facultative anaerobic - can grow either aerobically or anaerobically.

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12
Q

What does facultative anaerobic mean?

A

A bacteria than can grow aerobically or anaerobically.

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13
Q

Are staph. aureus infections typically localised or spreading?

A

localised - abscesses

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14
Q

Are strep. pyogenes infections typically localised or spreading?

A

spreading

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15
Q

Is staph. aureus or strep. pyogenes more antimicrobial resistant?

A

Staph. aureus

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16
Q

Is staph. aureus catalase negative or positive?

A

catalase positive

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17
Q

Is strep. pyogenes catalase negative or positive?

A

catalase negative

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18
Q

What does it mean if a bacteria is catalase positive?

A

It has the catalase enzyme, which converts H2O2 to O2

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19
Q

What bacteria is the most common cause of skin and wound infections, and abscesses?

A

Staph. aureus

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20
Q

Where is staph. aureus typically carried non-infectiously?

A

The nose

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21
Q

What toxin does staph. aeureus have to kill neutrophils?

A

PVL - panton valentine leukocidin.

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22
Q

What is bacterial coagulase?

A

A protein that sits on the surface of bacteria that converts fibrinogen to fibrin.

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23
Q

What is the function of bound bacterial coagulase?

A

Bound to the cell wall and converts fibrinogen to fibrin, causing clotting of the blood.

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24
Q

What protein/enzyme does S. aureus have that results in blood plasma clotting?

A

Coagulase

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25
Q

What are the infections commonly caused by strep. pyogenes?

A

Pharyngitis, skin infections, pneumonia, endocarditis, sepsis, rheumatic fever (from Group A streps)

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26
Q

What are the post-infectious conditions caused by strep. pyogenes?

A

Rheumatic fever, acute glomerulonephritis

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27
Q

Where is strep. pyogenes typically carried?

A

The pharynx/throat

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28
Q

What is the most important virulence factor of strep. pyogenes?

A

M protein

29
Q

What feature of strep. pyogenes allows it to repel phagocytes?

A

M protein in the bacterial cell wall provides a negative charge which repels negatively charge phagocytes.

30
Q

What are pyodermas?

A

purulent bacterial skin infections

31
Q

What are the 4 types of pyodermas in order of increasing severity?

A

Impetigo, folliculitis, furuncles, carbuncles

32
Q

What is the common name for impetigo?

A

school sores

33
Q

What are the 2 forms of impetigo?

A

Non-bullous & bullous

34
Q

What bacteria causes non-bullous impetigo?

A

Staph. aureus &/or strep. pyogenes

35
Q

What age group is most likely to develop non-bullous impetigo?

A

Children

36
Q

How does non-bullous impetigo present?

A

Red sores around the mouth and nose that dry to form golden coloured crusts.

37
Q

What bacteria causes bullous impetigo?

A

Staph. aureus

38
Q

What is the presentation of bullous impetigo?

A

Fluid filled vesicles (bullae) on the skin anywhere in the body

39
Q

What is the age group most affected by bullous impetigo?

A

All ages are affected.

40
Q

What is folliculitis?

A

Infection of hair follicles

41
Q

What is the presentation of folliculitis?

A

Small papules around hair follicles that evolve into pustules.

42
Q

What is the difference between papules & pustules in folliculitis?

A

Papules are hard, raised red lumps around follicles that evolve into pustules - small superficial abscesses.

43
Q

What are the treatments for folliculitis?

A

Topical antimicrobials, followed by oral antimicrobials in serious or extensive cases.

44
Q

What is the common name for furuncles?

A

Boils

45
Q

What condition progresses into the formation of a furuncle?

A

Folliculitis

46
Q

What is a furuncle?

A

Deeper infection of a hair follicle with pus, and local cellulitis surrounding the follicle.

47
Q

What bacteria typically causes a furuncle?

A

Staph. aureus

48
Q

What are the risk factors for developing a furuncle?

A

Diabetes, obesity, carriage of stap. aureus, immunosuppression

49
Q

What are carbuncles?

A

Extensive infection of a group of follicles

50
Q

Where are carbuncles typically found?

A

The neck, back, thighs

51
Q

What bacteria typically causes carbuncles?

A

Staph. aureus

52
Q

What is cellulitis?

A

Acute spreading of skin infection involving the dermis & hypodermis

53
Q

What are the symptoms of cellulitis?

A

Little necrosis, oedema/swelling, ill-defined margins of red skin merging smoothly with adjacent skin, pain, heat, tenderness, fever, etc.

54
Q

What are the complications of cellulitis?

A

Abscess, osteomyelitis, sepsis, necrotising fasciitis

55
Q

What bacteria most commonly cause cellultis?

A

gram-positive cocci - staph. aureus & strep. pyogenes

56
Q

What are the risk factors for cellulitis?

A

trauma, diabetes, obesity, age, immunosupression, vascular disease, pregnancy

57
Q

What is erysipelas?

A

Superficial cellulitis with lymphatic involvement.

58
Q

What are the symptoms of erysipelas?

A

bright red, well demarcated, hard, swollen lesion. accompanied by systemic symptoms such as fever, chills, malaise

59
Q

What is necrotizing fasciitis?

A

Rapid, spreading, destructive infection along the fascia

60
Q

What is fascia?

A

Fibrous connective tissue between the skin and muscle

61
Q

Why does necrotizing fasciitis have a high mortality?

A

It cause sepsis, which leads to multi-organ failure.

62
Q

What bacteria commonly cause necrotizing fasciitis?

A

usually polymicrobial - often staph. aureus & strep. pyogenes

63
Q

What are the typical treatments for pyodermas?

A

antimicrobials avoided unless advanced, topical antiseptics

64
Q

What are the typical treatments for carbuncles?

A

surgical drainage, antimicrobials

65
Q

How are advanced skin infection such as necrotising fasciitis and cellulitis initially treated?

A

Empiric therapy

66
Q

What is empiric therapy in terms of antimicrobial drugs?

A

The early delivery of broad spectrum antimicrobial drugs, despite not yet having a diagnosis of the bacteria present, to help prevent rapid spread in acute infections.

67
Q

What is the most commonly used antibiotic for Staph. aureus infections, and why?

A

Flucloxacillin, many strains are resistant to penicillin.

68
Q

What is the antimicrobial used to treat MRSA (methicillin resistant stapholococcus aureus) infections?

A

Vancomycin

69
Q

What is the antimicrobial most commonly used to treat strep. pyogenes infections?

A

penicillin

ELM2 - infection & immunity (22 decks)

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