Skin and Soft Tissue Infections Flashcards

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1
Q

Most common organisms associated with skin and soft tissue infections? (2)

A

Staph aureus

Group A Streptococcus pyogenes

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2
Q

How does the coagulase enzyme produced by staph aureus act as a virulence factor?

A

Activates fibrinogen and is important in abscess formation

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3
Q

What syndrome does the toxin TSST-1 (toxic syndrome one-1) cause?

A

Toxic shock syndrome, systemic illness

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4
Q

How does the enzyme hyaluronidase act as a virulence factor?

A

Produced by staph aureus, lyses fibrin clots and assists in spread of infection

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5
Q

What organism causes scalded skin syndrome in babies?

A

Staph aureus

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6
Q

Well recognised carriage sites of staph aureus on the human body?

A

Anterior nares, skin of axilla and groin

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7
Q

How does a capsule act as a virulence factor for streptococcus pyogenes?

A

Immunological disguise

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8
Q

How does M protein act as virulence factor for streptococcus pyogenes?

A

Adherence, helps to resist phagocytosis

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9
Q

Which organism produces these toxins: Streptolysin O, Streptolysin S, pyrogenic toxin

A

Streptococcus pyogenes

Pyrogenic toxin responsible for some of the severe manifestations of necrotising fasciitis

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10
Q

How can you detect the presence of a previous or recent streptococcal infection?

A

Antibodies to streptolysin O

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11
Q

Where does streptococcus pyogenes normally colonise on the human body?

A

Nasopharynx

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12
Q

Name the two post streptococcal syndromes

A

Rheumatic fever
Glomerulonephritis

Arise a few weeks after an infection. Immunologically related.

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13
Q

Aetiology of impetigo?

A

Staph aureus

Strep pyogenes

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14
Q

Complication of impetigo

A

Post-streptococcal glomerulonephritis

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15
Q

Treatment for impetigo

A

Topical fusidic acid/mupirocin

Flucloxacillin

Exclude from school

Strict hygiene, don’t share towels

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16
Q

What is folliculitis?

A

Superficial infection of hair follicle, caused by staph aureus, pus only in epidermis

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17
Q

What are carbuncles?

A

Infection of multiple adjacent follicles usually on the back of the neck

Inflammatory mass with multiple sinuses

Patient is often diabetic

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18
Q

What are furuncles?

A

Commonly known as boils

Infection of hair follicle that extends into dermis with more inflammation that folliculitis

Inflammatory nodule is present often with a hair seen emerging from this

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19
Q

Treatment of larger furuncles/carbuncles?

A

Incision and drainage

Abx not usually needed

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20
Q

Treatment of recurrent furunculosis

A

Occurs in staph aureus carriers (carried in their anterior nares) therefore topical MUPIROCIN on the anterior nares

Recurrence also occurs in diabetics

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21
Q

What is erysipela?

A

Form of cellulitis affecting most superficial layers of skin

More common in infants and elderly

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22
Q

Symptoms of erysipelas

A

Superficial cellulitis affecting infants and elderly

Abrupt onset with fever, chills, malaise

Raised lesions on red hot area of skin which is well demarcated

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23
Q

What area of the body does erysipelas affect?

A

Lower legs 70-80%

Face 5-10%

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24
Q

Tx of erysipelas

A

Penicillin, oral or IV

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25
Q

Which skin layer is affected by cellulitis?

A

Dermis and subcutaneous fat

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26
Q

Symptoms of cellulitis

A

Preceded by fever/flu like symptoms

Skin red, hot, swollen (peau d’orange)

Advancing diffuse edge

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27
Q

Risk factors for cellulitis (6)

A
Obesity
Venous insufficiency
Lymphoedema
Trauma
Athletes foot
Diabetes
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28
Q

Which organisms cause cellulitis?

A

MOSTLY will be staph aureus
Or strep pyogenes

BUT in cases of trauma it may be a more unusual cause (eg dog bite with Pasteurella and mixed anaerobes)

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29
Q

Treatment of mild cellulitis?

A

Oral flucloxacillin (covers both staph and strep)

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30
Q

Treatment of moderate to severe cellulitis?

A

IV flucloxacillin +/- benzylpenicillin

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31
Q

Treatment of cellulitis with penicillin allergy?

A

Clindamycin

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32
Q

Investigations for cellulitis?

A

Skin swab of any breaches

Blood cultures if severe

CLINICAL DIAGNOSIS

33
Q

Which animals have pasteurella mulocida in their bites?

A

Cats and dogs

34
Q

Which animals have anaerobes in their bites?

A

cats, dogs and humans

35
Q

Which animals have eikenella corrodens in their bites?

A

Humans

36
Q

Management of bites?

A

Prophylactic abx for high risk wounds and high risk patietns

CO-AMOXICLAV covers all relevent pathogens

Don’t forget tetanus

37
Q

Most common organism in surgical infection?

A

Staph aureus

38
Q

Surgical infection: organisms in contaminated or dirty wounds?

A

Coliform streps and anaerobes

39
Q

General management of surgical wound infections

A

Open and drain

Abx not always necessary

40
Q

Abx for surgical wound with staph aureus

A

Flucloxacillin OR clindamycin

41
Q

Abx for dirty surgical wound infection (eg staph, strep, coliforms, anaerobes)

A

Second generation cephalosporin such as:
CEFUROXIME + METRONIDAZOLE

OR

Co-amoxiclav

42
Q

4 types of chronic wound

A

Arterial
Venous
Pressure sores
Diabetic ulcers

43
Q

Symptoms of arterial ulcer

A
Weak or absent pulses
Reduced ABPI
Intermittent claudication
Skin hairless and shiny
Ulcer with well defined border
44
Q

Tx for arterial ulcer?

A

Revascularise with bypass grafting or angioplasty

45
Q

Symptoms of venous ulcer

A

Superior to medial malleolus
Haemosiderin deposits
Lipodermatosclerosis
Oedema

46
Q

Management for venous ulcer

A

Compression therapy

47
Q

Where do pressure ulcers arise?

A

Over sites of bony prominence

48
Q

Where do diabetic ulcers occur?

A

Mostly on plantar surface of foot

49
Q

How many diabetic patients have diabetic ulcers at any time?

A

4-20%

50
Q

True/false: diabetic ulcers are leading cause of traumatic amputations

A

FALSE, leading cause of NON-traumatic amputations. 40-60%

51
Q

Investigations for chronic wound infection

A

Swab wound bed after cleansing and removal of slough but BEFORE antiseptics and antibiotics

Tissue biopsies better than swabs

ONLY SAMPLE WHEN ?infection

Positive swab result is not a directive to treat

52
Q

Debriding options for chronic wounds (3)

A

Surgical
Chemical
Larvae

53
Q

Local antiseptics for chronic wounds (2)

A

Cadexomer iodine

Silver products

54
Q

General management of chronic wounds

A

Debridement, local antiseptics, and use of complex dressings to keep wound bed moist

Reserve antibiotics for systemic infection

55
Q

What is single most important pathogen in diabetic foot infection?

A

Staph aureus

May be polymicrobial in deep or severe infection

56
Q

Describe a mild diabetic foot infection

A

<2cm radius of cellulitis around wound

57
Q

Describe a moderate diabetic foot infection

A

> 2cm cellulitis radius

Deep infection

58
Q

Describe a severe diabetic foot infection

A

Deep infection

Systemic sepsis

59
Q

What is necrotising fasciitis?

A

A RARE, life-threatening, rapidly progressive subcutanous infection which tracks along fascial planes

60
Q

How does necrotising fasciitis spread?

A

Tracks along the fascial planes

61
Q

3 types of necrotising fasciitis?

A

Polymicrobial NF

Group A strep NF (flesh eating)

Clostridial myonecrosis (gas gangrene)

62
Q

When does polymicrobial necrotising fasciitis occur?

A

After trauma or surgery

An example is Fournier’s gangrene

Involves staph, strep, anaerobes, coliforms, and aerobic gram negatives

63
Q

What is another name for Group A streptococcal NF?

A

Flesh eating NF

Can occur in fit and healthy people

Result of minor trauma

64
Q

What is another name for Clostridial myonecrosis?

A

Gas gangrene, caused by Clostridium perfringens

65
Q

Symptoms and signs of necrotising fasciitis

A

HAVE HIGH SUSPICION INDEX

Overlying cellulitis
Pain OUT OF KEEPING with signs

Skin necrosis
Crepitus
Confusion
Hypotension

66
Q

How to confirm necrotising fasciitis diagnossi?

A

Surgical exploration

67
Q

Treatment of necrotising fasciitis

A

Surgical emergency
Aggressive debridement
ICU

Antibiotics: High doses of benzylpenicillin, clindamycin, ciprofloxacin

68
Q

What 3 abx are used for necrotising fiasciitis?

A

BCC

Benzylpenicillin
Clindamycin
Ciprofloxacin

69
Q

Causes of ringworm (3)

A

Trichophyton
Microsporum
Epidermophyton

70
Q

How is ringworm/tinea spread?

A

Zoonotic, human to human (shared towels, hairbrushes)

71
Q

How is ringworm diagnosed?

A

Clinical appearance

Direct microscopic exam of scales in potassium hydroxide

Culture of scrapings

FLUORESCENCE UNDER WOOD’S LIGHT FOR TINEA CAPITIS

72
Q

Tx for tinea/ringworm?

A

Topical imidazoles 2-4 wks

Oral terbinafine for resistant cases

73
Q

Which antibiotics increase risk of MRSA?

A

Quinolones

Cephalosporins

74
Q

Treatment for mild MRSA infection?

A

Tetracyclines

75
Q

Treatment for severe MRSA infection?

A

Glycopeptides:

-IV VACNOMYCIN/ TEICOPLANIN

76
Q

What is CA-MRSA?

A

Community associated MRSA

Affects young, healthy adults and children

No associated risk factors

77
Q

What organism produces the toxin Panton-Valentin Leukocid (PVL)

A

CA-MRSA

78
Q

What is the infection rate of mammal bites?

A

30-50%