Skin and Tissue Infection Flashcards

1
Q

What is impetigo?

A

A superficial, contagious, blistering infection of the skin caused by the bacteria Staphylococcus aureus and Streptococcus pyogene

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2
Q

What are the different types of impetigo?

A
  • Bullous
  • Non-bullous
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3
Q

What is the most common form of impetigo?

A

Non-bullous impetigo - 70% of cases

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4
Q

What layer of the skin does impetigo affect?

A

Epidermis

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5
Q

What is bullous impetigo caused by?

A

Staphylococcus - produces exfoliative toxin

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6
Q

How do bullae form in impetigo?

A

Toxin that contains serine proteases acting on desmoglein 1. This process allows S. aureus to spread under the s.corneum in the space formed by the toxin, causing the epidermis to split just below the stratum granulosum.

Large blisters then form in the epidermis with neutrophil and, often, bacterial migration into the bullous cavity. In bullous impetigo, the bullae rupture quickly, causing superficial erosion and a yellow crust

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7
Q

What are the main causative agents of impetigo?

A
  • Staphylococcus
  • Group A B-haemolytic strep
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8
Q

What causes non-bullous impetigo?

A

Streptococcus pyogenes

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9
Q

What is the following?

A

Impetigo

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10
Q

What might you see on examination in someone with impetigo?

A

Erosions that have a yellowish to golden crust on an erythematous base, with patchy distribution, often in the peri-oral and peri-nasal area, although they can occur anywhere on the body.

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11
Q

How would you manage someone with impetigo?

A

Topical antibiotics

  • Fusidic acid
  • Flucloxacillin

Hygeine advice

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12
Q

What is erysipelas?

A

A distinct form of superficial cellulitis with notable lymphatic involvement and is raised, sharply demarcating it from uninvolved skin

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13
Q

What layer of the skin does erysipelas affect?

A

Dermis

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14
Q

What is the cause of erysipelas?

A

Strep. pyogenes

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15
Q

What are features of erysipelas?

A
  • Painful, red area
  • Fever
  • Regional lymphadenopathy and lymphangitis
  • Distinct elevated borders
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16
Q

What is the following?

A

Erysipelas

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17
Q

Where does erysipelas most commonly affect?

A

The face

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18
Q

How would you treat erysipelas?

A

Benzylpenicillin + Flucloxacillin - consider IV if serious

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19
Q

What is cellulitis?

A

An acute spreading infection of the skin with visually indistinct borders that principally involves the dermis and subcutaneous tissue

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20
Q

What layers does cellulitis affect?

A

Dermis and subcut tissue

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21
Q

What organisms are implicated in cellulitis?

A
  • B-haemolytic streps
  • Staph. aureus
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22
Q

What are signs of a cellulitis?

A
  • Pain
  • Swelling
  • Warmth
  • Erythema - no distinct borders
  • Systemic upset plus fever
  • Lymphadenopathy/lymphangitis
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23
Q

Where does cellulitis most commonly affect?

A

Lower legs

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24
Q

What is the following?

A

Ascending lymphangitis

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25
Q

What is the following?

A

Cellulitis

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26
Q

How would you treat a mild cellulitis empirically?

A

Oral Flucloxacillin or clarythromycin - 7-14 days

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27
Q

How would you treat moderate to severe cellulitis?

A

IV Flucloxacillin, switch to oral fluclox/doxycycline

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28
Q

What is folliculitis?

A

Pustular infection of a single hair follicle which can occur in clusters typically on head, back buttocks and extremities

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29
Q

What is the cause of folliclitis?

A

S. Aureus

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30
Q

What are the features of folliculitis?

A
  • Circumscribed, pustular infection of a hair follicle
  • Up to 5mm in diameter
  • Present as small red papules - Central area of purulence that may rupture and drain
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31
Q

Where is folliculitis typically found?

A

Head, back, buttocks and extremities

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32
Q

What is furunculosis?

A

An inflammatory infection of a single hair follicle that extends deep into dermis and subcutaneous tissue. Usually affecting moist hairy areas of body

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33
Q

What is the most common cause of furunculosis?

A

S. aureus

34
Q

What are features of furunculosis?

A
  • Single hair follicle-associated inflammatory nodule
  • Extending into dermis and subcutaneous tissue
  • May spontaneously drain purulent material
35
Q

What are risk factors for folliculitis?

A
  • Obesity
  • Diabetes mellitus
  • Atopic dermatitis
  • Chronic kidney disease
  • Corticosteroid use
36
Q

What are carbuncles?

A

Large abscess involving multiple adjacent hair follicles, which tend to by multiseptated. These may drain spontaneously

37
Q

What are features of carbuncles?

A

Infection extends to involve multiple furuncles

  • Multiseptated abscesses
  • Purulent material expressed from multiple sites
38
Q

Where are carbuncles most commonly found?

A
  • Back of neck
  • Posterior trunk
  • Thigh
39
Q

How would you treat folliculitis?

A

Topical antibiotics

40
Q

How would you treat a furuncle?

A

Topical/oral antibiotics

41
Q

How would you manage someone with a carbuncle?

A

Hospital admission, surgery and IV Abx

42
Q

What is necrotising fasciitis?

A

A life-threatening subcutaneous soft-tissue infection that may extend to the deep fascia, but not into the underlying muscle. The causal organisms may be aerobic, anaerobic, or mixed flora

43
Q

What are the main clinical forms of necrotising fasciitis?

A
  • Type I - polymicrobial
  • Type II - monomicrobial infection with Streptococcus pyogenes (group A streptococci)
44
Q

What organisms are commonly involved in type I necrotising fasciititis?

A

An aerobe and a facultative anaerobe

  • Streptococci
  • Staphylococci
  • Enterococci
  • Gram negative bacilli
  • Clostridium
45
Q

What are the majority of superificial skin infections caused by?

A
  • S. aureus
  • S. pyogenes
46
Q

What layers are involved in necrotizing fasciitis?

A

Infection extends through the fascia but not into the underlying muscle, and tracks along fascial planes extending beyond the area of overlying cellulitis

47
Q

What are symptoms of necrotizing fasciitis?

A

Rapid onset, sequential development of:

  • Severe, unremitting pain around site
  • Fever
  • Delerium
48
Q

What are signs of necrotising fasciiitis?

A
  • Crepitus
  • Haemorrhagic bullae
  • Skin necrosis
  • Anaesthesia at site of infection
49
Q

How would you diagnose necrotising fasciitis?

A

Clinical diagnosis

50
Q

How would you manage someone with necrotizing fasciitis?

A
  • ABx - Fluclox + benpen + Gentamicin + Clindamycin
  • Urgent surgical debridement +/- amputation
51
Q

What is the overall mortality associated with necrotising fasciitis?

A

17-40%

52
Q

What would you trat GAS necrotizing fasciitis?

A

Benzylpenicillin and clindamycin

53
Q

What is pyomyositis?

A

A bacterial infection of the skeletal muscles which results in a pus-filled abscess. Pyomyositis is most common in tropical areas but can also occur in temperate zones.

54
Q

Where does pyomyositis most commonly occur?

A
  • Thigh
  • Calf
  • Arms
  • Gluteal region
  • Chest wall
  • Psoas muscle
55
Q

What are predisposing factors to the development of pyomyositis?

A
  • Diabetes mellitus
  • HIV/immunocompromised
  • Intravenous drug use
  • Rheumatological diseases
  • Malignancy
  • Liver cirrhosis
56
Q

What are features of pyomyositis?

A
  • Fever
  • Pain
  • Woody induration of affected muscle
57
Q

How would you investigate suspectedd pyomyositis?

A
  • Clinical diagnosis
  • Imaging - CT/MRI
58
Q

How would you manage someone with pyomyositis?

A
  • Drainage
  • Antibiotics
59
Q

Where are features of septic bursitis?

A
  • Fever
  • Pain on movement
  • Peribursal cellulitis
  • Swelling
  • Warmth
60
Q

How would you investigate someone with septic arthritis?

A
  • Clinical diagnosis
  • Fluid aspiration
61
Q

What is infective tenosynovitis?

A

Infection of the synovial sheats that surround tendons

62
Q

What are organisms implicated in infective tenosynovitis?

A
  • S. aureus
  • Strep
  • Mycobacteria
  • Fungi
63
Q

What are features of infective tenosynovitis?

A
  • Erythematous fusiform swelling of finger
  • Pain with extension of finger
  • Held in a semiflexed position
  • Tenderness over the length of the tendon sheath
64
Q

How would you manage someone with infective tenosynovitis?

A
  • Abx
  • Hand surgeon referral
65
Q

What is staphylococcal scalded sking syndrome?

A

An illness characterised by red blistering skin that looks like a burn or scald, hence its name staphylococcal scalded skin syndrome.

The scalded skin syndrome is caused by a toxin-secreting strain of S. aureus.

66
Q

What toxin is implicated in SSSS?

A

Exfoliatin - causes intra-epidermal cleavage at the level of the stratum corneum leading to the formation of large flaccid blisters that shear readily.

67
Q

Who does SSSS most commonly affect?

A

Children under the age of 5

68
Q

How would you treat staph scalded skin syndrome?

A

IV fluids and flucloxacillin

69
Q

What is toxic shock syndrome?

A

A condition of shock caused by bacterial super antigens

70
Q

What organisms cause toxic shock syndrome?

A
  • Staphylococcus
  • Streptococcus
71
Q

What toxin is implicated in TSS?

A

TSST-1 - causes cytokine release with abrupt onset of fever and shock, with a diffuse macular rash and desquamation of the palms and soles

72
Q

What are features of TSS?

A
  • Shock
  • Confusion
  • Fever
  • Rash
  • Diarrhoea
  • Myalgia
  • Desquamation of hands and feet
73
Q

What can be a cause of TSS in females?

A

Indwelling tampon

74
Q

What is a class I surgical wound?

A

Clean wound (respiratory, alimentary, genital or infected urinary systems not entered)

75
Q

What is a class II surgical wound?

A

Clean-contaminated wound (above tracts entered but no unusual contamination)

76
Q

What is a class III surgical wound?

A

Contaminated wound (Open, fresh accidental wounds or gross spillage from the gastrointestinal tract)

77
Q

What is a class IV surgical wound?

A

Infected wound (existing clinical infection, infection present before the operation)

78
Q

What is MRSA?

A

Methicillin-resistnat staphylococcus aureus

79
Q

Where is MRSA most commonly acquired?

A

Hospital acquired infection

80
Q

What is MRSA resistant to?

A

Resistant to penicillin and isolated resistance to other β-lactam antibiotics such as meticillin (now rarely used) and flucloxacillin

81
Q

What is MRSA most commonly found in?

A

Surgical wounds

82
Q

What antibiotics would you use for MRSA infection?

A
  • Vancomycin
  • Linezolid
  • Teicoplanin
  • Daptomycin