Skin and Soft Tissue Infections Flashcards

1
Q

What is impetigo?

A

Superficial skin infection

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2
Q

Describe the character of impetigo skin lesions?

A
  • Multiple vesicular lesions on erythematous base
  • Golden crus highly suggestive of this diagnosis
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3
Q

What is impetigo most and least commonly due to?

A

Most commonly due to staph aureus, least commonly due to strep pyogenes

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4
Q

What infection is this?

A

Impetigo

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5
Q

Who does impetigo commonly infect?

A

Commonly affects children, is highly infectious

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6
Q

What are some risk factors for impetigo?

A
  • Skin abrasions
  • Minor trauma
  • Burns
  • Poor hygiene
  • Insect bites
  • Chickenpox
  • Eczema
  • Atopic dermatitis
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7
Q

What is the treatment of impetigo?

A
  • Small area
    • Topical antibiotics alone
  • Large area
    • Topical treatment and oral antibiotics (such as flucloxacillin)
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8
Q

What is erysipelas?

A

Infection of the upper dermis

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9
Q

What is the presentation of erysipelas?

A
  • Painful, red area (no central clearing)
  • Associated fever
  • Regional lymphadenopathy and lymphangitis
  • Typically has distinct elevated borders
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10
Q

What is erysipelas most commonly due to?

A

Most commonly due to strep pyogenes

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11
Q

What infection is this?

A

Erysipelas

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12
Q

Where does erysipelas mostly affect?

A

Mostly affects lower limbs, then face

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13
Q

What is cellulitis?

A

Diffuse skin infection involving deep dermis and subcutaneous fat

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14
Q

What is the presentation of cellulitis?

A
  • Spreading erythematous area with no distinct borders
  • Fever is common
  • Possible source of bacteraemia
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15
Q

What are the most likely organisms that cause cellulitis?

A

Most likely organisms are strep pyogenes and staph aureus

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16
Q

What infection is this?

A

Cellulitis

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17
Q

What are risk factors for cellulitis?

A
  • Diabetes
  • Tinea pedis
  • Lymphoedema
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18
Q

What is the treatment for erysipelas?

A
  • Combination of anti-staph and anti-strep antibiotics
  • In extensive disease, admission for IV antibiotics
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19
Q

What is the treatment of cellulitis?

A
  • Combination of anti-staph and anti-strep antibiotics
  • In extensive disease, admission for IV antibiotics
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20
Q

What are examples of hair associated infections?

A
  • Folliculitis
  • Furunculosis
  • Carbuncles
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21
Q

What is folliculitis?

A

Circumscribed, pustular infection of a hair follicle

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22
Q

Describe the character of folluculitis lesions?

A
  • Small red papules
  • Up to 5mm in diameter
  • Central area of purulence that may rupture and drain
  • Typically found on head, back, bum and extremities
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23
Q

What infection is this?

A

Folliculitis

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24
Q

What is the most common organism causing folliculitis?

A

Staph aureus

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25
Q

What is the treatment for folliculitis?

A
  • No treatment or topical antibiotics
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26
Q

What is furunculosis?

A

Single hair follicle associated inflammatory nodule extending into dermis and subcutaneous tissue

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27
Q

What is furunculosis commonly refered to as?

A

Boils

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28
Q

Describe the character of furunculosis lesions?

A
  • Usually affects moist, hairy, friction prone areas of body
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29
Q

What infection is this?

A

Furunculosis

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30
Q

What organism most commonly causes furunculosis?

A

Staph aureus

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31
Q

What are risk factors for furunculosis?

A
  • Obesity
  • Diabetes
  • Atopic dermatitis
  • CKD
  • Corticosteroid use
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32
Q

Are systemic symptoms with furunculosis common?

A
  • Systemic symptoms uncommon
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33
Q

What is the treatment of furunculosis?

A
  • No treatment or topical antibiotics
  • If not improving oral antibiotics
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34
Q

What is carbuncle?

A

Occurs when infection extends to involve multiple furuncles

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35
Q

Describe the character of carbuncle lesions?

A
  • Often located back of neck, posterior trunk or thigh
  • Multiseptated abscesses
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36
Q

Are systemic symptoms common with carbuncle?

A
  • Systemic symptoms common
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37
Q

What infection is this?

A

Carbuncle

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38
Q

What is the treatment for carbuncle?

A
  • Surgery
  • IV antibiotics
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39
Q

Necrotising fasculitis is a…

A

Infectious disease emergency

40
Q

What are risk factors for necrotising fasculitis?

A
  • Diabetes
  • Surgery
  • Trauma
  • Peripheral vascular disease
  • Skin popping
41
Q

What are the different types of necrotising fasculitis?

A
  • Type 1
    • Refers to mixed aerobic and anaerobic infection
    • Such as diabetic foot infection, or Fournier’s gangrene
    • Organisms includes
      • Streptococci
      • Staphylococci
      • Enterococci
      • Gram negative bacilli
      • Clostridium
  • Type 2
    • Is monomicrobial
    • Normally associated with strep pyogenes
42
Q

What organisms cause type 1 necrotising fascultiis?

A
  • Streptococci
  • Staphylococci
  • Enterococci
  • Gram negative bacilli
  • Clostridium
43
Q

What organism is type 2 necrotising fasculitis typically associated with?

A

Strep pyogenes

44
Q

What is the presentation of necrotising fasculitis?

A
  • Rapid onset
  • Sequential development of erythema, extensive oedema and severe paion
  • Haemorrhagic bullae, skin necrosis and crepitus may develop
  • Systemic features
    • Fever
    • Hypotension
    • Tachycardia
    • Delerium
    • Multiorgan failure
45
Q

What investigations are done for necrotising fasculitis?

A
  • Surgical review is mandatory
  • Imaging may help but could delay treatment
46
Q

What is the treatment for necrotising fasculitis?

A
  • Antibiotics should be broad spectrum
    • Flucloxacillin
    • Gentamicin
    • Clindamycin
47
Q

What is pyomyositis?

A

Purulent infection deep within striated muscle

48
Q

What is the presentation of pyomyositis?

A
  • Often manifests as abscess
  • Common sites
    • Thigh
    • Calf
    • Arms
    • Gluteal region
    • Chest wall
    • Psoas muscle
  • Fever and pain
  • If untreated can lead to septic shock and death
49
Q

What are risk factors for pyomyositis?

A
  • Diabetes mellitus
  • HIV/immunocompromised
  • Intravenous drug use
  • Rheumatological diseases
  • Malignancy
  • Liver cirrhosis
50
Q

What organism is the most common cause of pyomyositis?

A

Staph aureus

51
Q

What investigations should be doen for pyomyositis?

A
  • CT/MRI
52
Q

What is the treatment for pyomyositis?

A
  • Drain with antibiotic cover depending on gram stain and culture results
53
Q

What are bursae?

A

Small sac-like cavities that contain fluid and are lined by synovial membrane

54
Q

Where are bursae located?

A

Located subcutaneously or between bony prominences or tendons

55
Q

What are risk factors for septic bursitis?

A
  • Infection often from adjacent skin infection
  • Rheumatoid arthritis
  • Alcoholism
  • Diabetes mellitus
  • Intravenous drug abuse
  • Immunosuppression
  • Renal insufficiency
56
Q

What infection is this?

A

Septic bursitis

57
Q

What is the presentation of septic bursitis?

A
  • Peribursal cellulitis, welling and warmth
  • Fever and pain on movement
58
Q

Septic bursitis is diagnosed by what?

A

Diagnosis based on aspiration of fluid

59
Q

What organism is the most common cause of septic bursitis?

A

Most common cause is staph aureus, rarer organisms include:

  • Gram negatives
  • Mycobacteria
  • Brucella
60
Q

What is infectious tenosynovitis?

A

Infection of the synovial sheets that surround tendons

61
Q

Where does infectious tenosynovitis most commonly affect?

A

Most commonly affects flexor muscle and associated tendons of the hand

62
Q

What is the most common cause of infectious tenosynovitis?

A

Most common cause is staph aureus and streptococci, chronic infections occur due to mycobacteria and fungi

63
Q

What is the presentation of infectious tenosynovitis?

A
  • Erythematous fusiform swelling of finger
  • Hand held in semiflexed position
  • Tenderness over the length of the tendon sheet with pain on extension of finger
64
Q

What is the treatment of infectious tenosynovitis?

A
  • Empiric antibiotics
  • Hand surgeon to review
65
Q

What are toxin mediated syndromes often due to?

A

Often due to super antigens such as group of pyrogenic exotoxins

66
Q

Describe the pathophysiology of toxin mediated syndromes?

A
  • Do not activate immune system via normal contact between APC and T cells
  • Superantigens bypass this and attach directly to T cell receptors activating them
  • Massive bursts of cytokines released
  • Leads to endothelial leakage, haemodynamic shock, multiorgan failure and maybe death
67
Q

What are toxin mediated syndromes mostly due to?

A
  • Some strains of staph aureus
    • TSST1
    • ETA and ETB
  • Some strains of streptococcus pyogenes
    • TSST1
68
Q

What toxins can staph aureus release that causes toxin mediated syndromes?

A
  • TSST1
  • ETA and ETB
69
Q

What toxin can strep pyogenes release that causes toxin mediated syndromes?

A

TSST1

70
Q

What is the diagnostic criteria for staph TSS?

A
  • Fever
  • Hypotension
  • Diffuse macular rash
  • Three of following organs involved
    • Liver, blood, renal, GI, CNS, muscular
  • Isolation of staph aureus from mucosal or normally sterile sites
  • Production of TSST1 by isolate
  • Development of antibody to toxin
71
Q

What does TSS stand for?

A

Toxin shock syndrome

72
Q

Does strap or strep TSS have a higher mortality rate?

A

Strep (50% vs 5%)

73
Q

What is the treatment for toxin shock syndrome?

A
  • Remove offending agent (ex tampon)
  • Intravenous fluids
  • Inotropes
  • Antibiotics
  • Intravenous immunoglobulins
74
Q

What often causes toxin shock syndrome?

A

Tampons

75
Q

What is staph scaled skin syndrome?

A

Infection due to particular strain of staph aureus producing the exfoliative toxin A or B

76
Q

What is the presentation of staph scaled skin syndrome?

A
  • Widespread bullae and skin exfoliation
  • Usually occurs in children but rarely in adults
77
Q

hat is the treatment of staph scaled skin syndrome?

A
  • IV fluids and antimicrobials
78
Q

What infection is this?

A

Staph scaled skin syndrome

79
Q

What is the Penton-Valentine Leucocodin (PVL) toxin?

A

Is a gamma haemolysin

Can be transferred from one strain of staph to another including MRSA

80
Q

Describe the character os lesions due to PVL toxin?

A
  • Recurrent boils
81
Q

What is the treatment of PVL toxin?

A
  • Antibiotics to reduce toxin production
82
Q

What can PVL toxin cause?

A

Can cause SSTI (skin and soft tissue infection) and haemorrhagic pneumonia

83
Q

What does SSTI stand for?

A

Skin and soft tissue infection

84
Q

Where do IV catheter associated infections originate?

A

Nosocomial (originates in hospital) infection

85
Q

Desribe the pathogenesis of IV catheter associated infections?

A
  • Starts as local SST inflammation
  • Progresses to cellulitis and even tissue necrosis
86
Q

What are risk factors for IV catheter associated infections?

A
  • Continuous infusion >24 hours
  • Cannula in situ >72 hours
  • Cannula in lower limb
  • Patients with neurological/neurosurgical problems
87
Q

What organism most commonly causes IV catheter associated infections?

A

Most common organism is staph aureus (MSSA and MRSA), which commonly forms a biofilm which then spills into bloodstream

88
Q

How are IV catheter associated infections diagnosed?

A
  • Made clinically or by positive blood cultures
89
Q

What is the treatment for IV catheter associated infections?

A
  • Remove cannula
  • Express any pus from the thrombophlebitis
  • Antibiotics for 14 days
  • Echocardiogram
90
Q

What are ways to prevent IV catheter associated infections?

A
  • Do not leave unused cannula
  • Do not insert cannulae unless you are using them
  • Change cannulae every 72 hours
  • Monitor for thrombophlebitis
  • Use aseptic technique when inserting cannulae
91
Q

What are the different classification of surgical wounds?

A
  • Class 1
    • Clean wound (respiratory, alimentary, genital or infected urinary systems not entered)
  • Class 2
    • Clean-contaminated wound (above tracts entered but no unusual contamination)
  • Class 3
    • Contaminated wound (Open, fresh accidental wounds or gross spillage from the gastrointestinal tract)
  • Class 4
    • Infected wound (existing clinical infection, infection present before the operation)
92
Q

What are some examples of surgical site infection causative organisms?

A
  • Staph aureus (incl MSSA and MRSA)
  • Coagulase negative Staphylococci
  • Enterococcus
  • Escherichia coli
  • Pseudomonas aeruginosa
  • Enterobacter
  • Streptococci
  • Fungi
  • Anaerobes
93
Q

What are some risk factors for surgical site infections?

A
  • Patient associated
    • Diabetes
    • Smoking
    • Obesity
    • Malnutrition
    • Concurrent steroid use
    • Colonisation with Staph aureus
  • Procedural factors
    • Shaving of site the night prior to procedure
    • Improper preoperative skin preparation
    • Improper antimicrobial prophylaxis
    • Break in sterile technique
    • Inadequate theatre ventilation
    • Perioperative hypoxia
94
Q

How are surgical site infections diagnosed?

A
  • Send pus/infection tissue for culture
  • Aim for deep structures with swabs not superficial
95
Q

What is the treatment for surgical site infections?

A
  • Antibiotics to target likely organisms