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Systems: Infection AB > Skin and Soft Tissue Infections > Flashcards

Skin and Soft Tissue Infections Flashcards

1
Q

What things should be considered with skin and soft tissue infections?

A
  • Site
  • Organism
  • Host
  • Environment
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2
Q

What should be considered about the site of infection?

A

-Possible complications with specific sites (ex; abdo, face)

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3
Q

What should be considered about the organism causing infection?

A

Gram negative or gam positive

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4
Q

What should be considered about the infected host?

A
  • Diabetes leading to neuropathy and vasculopathy
  • Immunosuppression
  • Renal failure
  • Milroy’s disease (lymphatic system has not developed in specific part of the body, usually a limb)
  • Predisposing skin conditions (ex; atopic dermatitis)
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5
Q

What should be considered about the environment with infection?

A
  • Drug-resistant strains (MRSA)
  • Drug interactions
  • Drug allergies
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6
Q

What is impetigo?

A

A highly infection superficial skin infection

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7
Q

What is the presentation of impetigo?

A
  • Multiple vesicular lesions on an erythematous base

- Golden crust is highly suggestive of this diagnosis

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8
Q

What organisms cause impetigo?

A
  • Most commonly due to Staph aureus

- Less commonly Strep pyogenes

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9
Q

Where does impetigo usually affect?

A

Usually occurs on exposed parts of the body including face, extremities and scalp

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10
Q

Who usually gets impetigo?

A

Children aged 2-5

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11
Q

What are the predisposing factors for impetigo?

A
  • Skin abrasions
  • Minor trauma
  • Burns
  • Poor hygiene
  • Insect bites
  • Chickenpox
  • Eczema
  • Atopic dermatitis
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12
Q

What is the treatment for impetigo?

A
  • Small areas can be treated with topical antibiotics alone

- Large areas need topical treatment and oral antibiotics (ex flucloxacillin)

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13
Q

What is erysipelas?

A

Infection of the upper dermis with a high recurrence rate (30% withi 3 years)

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14
Q

How does erysipelas present?

A
  • Painful, red area (no central clearing)
  • Associated fever
  • Regional lymphadenopathy and lymphangitis
  • Typically has distinct elevated borders
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15
Q

What organisms is commonly responsible for erysipelas?

A

Strep. pyogenes

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16
Q

Where does erysipelas usually affect?

A
  • 70-80% of cases involves the lower limbs
  • 5-20% affect the face
  • Tends to occur in areas of pre-existing lymphoedema, venous stasis, obesity, paraparesis, diabetes mellitus
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17
Q

What is cellulitis?

A

Diffuse skin infection involving deep dermis and subcutaneous fat

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18
Q

How does cellulitis present?

A
  • Presents as a spreading erythematous area with no distinct borders
  • Fever is common
  • Regional lymphadenopathy and lymphangitis
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19
Q

What are the most likely organisms involved in cellulitis?

A
  • Strep pyogenes

- Staph aureus

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20
Q

What are the predisposing factors for cellulitis?

A
  • Diabetes mellitus
  • Tinea pedis
  • Lymphoedema
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21
Q

What is the treatment for erysipelas?

A
  • A combination of anti-staphylococcal and anti-streptococcal antibiotics
  • In extensive disease, admission for intravenous antibiotics and rest
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22
Q

What is the treatment for cellulitis?

A
  • A combination of anti-staphylococcal and anti-streptococcal antibiotics
  • In extensive disease, admission for intravenous antibiotics and rest
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23
Q

Give examples of hair associated infections.

A
  • Folliculitis
  • Furunculosis
  • Carbuncles
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24
Q

What is folliculitis?

A
  • A circumscribed, pustular infection of a hair follicle, up to 5mm in diameter
  • Benign
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25
Q

How does folliculitis present?

A
  • Present as small red papules
  • Central area of purulence that may rupture and drain
  • Absence of constitutional symptoms
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26
Q

Where does folliculitis typically occur?

A

Head, back, buttocks and extremities

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27
Q

What is the most common organism in folliculitis?

A

Staph aureus

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28
Q

What is furunculosis?

A
  • Furuncles are commonly referred to as boils.

- Single hair follicle-associated inflammatory nodule which extends into the dermis and subcutaneous tissue

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29
Q

Where does furunculosis commonly affect?

A

Moist, hairy friction-prone areas of the body (face, axilla, neck and buttocks)

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30
Q

What can furuncles spontaneously do?

A

Drain purulent material

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31
Q

What is the most common organism in furunculosis?

A

Staph aureus

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32
Q

What are the risk factors for furunculosis?

A
  • Obesity
  • Diabetes mellitus
  • Atopic dermatitis
  • Chronic kidney disease
  • Corticosteroid use
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33
Q

When does carbuncle usually occur?

A

When infection extends to involve multiple furuncles

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34
Q

Where do carbuncles usually occur?

A

Often on the back of the neck, posterior trunk or thigh

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35
Q

What do carbuncles present?

A
  • Multiseptated abscesses
  • May express purulent material from multiple sites
  • Constitutional symptoms are common
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36
Q

What is the treatment for folliculitis?

A

No treatment or topical antibiotics

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37
Q

What is the treatment for furunculosis?

A
  • No treatment or topical antibiotics

- Oral antibiotics may be necessary if no improvement

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38
Q

What is the treatment for carbuncles?

A

Often require admission to hospital, surgery and IV antibiotics

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39
Q

What is necrotising fasciitis?

A

An infectious disease emergency

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40
Q

Where can necrotising fasciitis affect?

A

Any site

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41
Q

What are the predisposing factors for necrotising fasciitis?

A
  • Diabetes mellitus
  • Surgery
  • Trauma
  • Peripheral vascular disease
  • Skin popping
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42
Q

What is type 1 necrotising fasciitis?

A

Type I refers to a mixed aerobic and anaerobic infection (diabetic foot infection, Fournier’s gangrene)

43
Q

What organisms are implicated in type 1 necrotising fasciitis?

A
  • Streptococci
  • Staphylococci
  • Enterococci
  • Gram negative bacilli
  • Clostridium
44
Q

What is type 2 necrotising fasciitis?

A

Monomicrobial infection

45
Q

What organism is usually implicated in type 2 necrotising fasciitis?

A

Strep. pyogenes

46
Q

How does necrotising fasciitis present?

A
  • Rapid onset
  • Sequential development of erythema, extensive oedema and severe, unremitting pain
  • Haemorrhagic bullae, skin necrosis and crepitus may develop
  • Systemic features include fever, hypotension, tachycardia, delirium and multiorgan failure
  • Anaesthesia at site of infection is highly suggestive of this disease
47
Q

What is there high risk of in necrotising fasciitis?

A

Compartment syndrome

48
Q

How should necrotising fasciitis be managed?

A

Surgical review is mandatory

Imaging may help but could delay treatment

Antibiotics should be broad spectrum

  • Flucloxacillin
  • Gentamicin
  • Clindamycin
49
Q

What is pyomyositis?

A
  • Purulent infection deep within striated muscle, often manifesting as an abscess
  • Infection is often secondary to seeding into damaged muscle
50
Q

Where does pyomyositis affect?

A

Common sites

  • Thigh
  • Calf
  • Arms
  • Gluteal region
  • Chest wall
  • Psoas muscle

Can affect multiple sites

51
Q

How can pyomyositis present?

A

Can present with fever, pain and woody induration of affected muscle

52
Q

If left untreated, what can pyomyositis lead to?

A

Septic shock and death

53
Q

What are the predisposing factors fro pyomyositis?

A
  • Diabetes mellitus
  • HIV/immunocompromised
  • Intravenous drug use
  • Rheumatological diseases
  • Malignancy
  • Liver cirrhosis
54
Q

What organisms can cause pyomyositis?

A
  • Commonest:Staph aureus
  • Gram positive and negatives
  • TB
  • Fungi
55
Q

How is pyomyositis investigated?

A

CT or MRI

56
Q

How is pyomyositis treated?

A

Treatment is drainage with antibiotic cover depending on Gram stain and culture results

57
Q

What are bursae?

A
  • Bursae are small sac-like cavities that contain fluid and are lined by synovial membrane
  • Located subcutaneously between bony prominences or tendons
  • Facilitate movement with reduced friction
58
Q

How does septic bursitis commonly occur?

A

Infection spreads from adjacent skin infection

59
Q

What predisposing factors are there for septic bursitis?

A
  • Rheumatoid arthritis
  • Alcoholism
  • Diabetes mellitus
  • Intravenous drug abuse
  • Immunosuppression
  • Renal insufficiency
60
Q

How does septic bursitis present?

A
  • Peribursal cellulitis, swelling and warmth are common

- Fever and pain on movement also seen

61
Q

How is septic bursitis diagnosed?

A

Aspiration of the fluid

62
Q

What organisms can cause septic bursitis?

A

-Commonest: staph aureus

Rarer organisms

  • Gram negatives
  • Mycobacteria
  • Brucella
63
Q

What is infectious tenosynovitis?

A

Infection of the synovial sheats that surround tendons

64
Q

Where does infectious tenosynovitis commonly occur?

A

Flexor muscle-associated tendons and tendon sheaths of the hand most commonly involved

65
Q

What event can incite infectious tenosynovitis?

A

Penetrating trauma

66
Q

What organisms can cause infectious tenosynovitis?

A

Most common
-Staph aureus

Chronic infection

  • Mycobacteria
  • Fungi

Possibility of disseminated gonococcal infection

67
Q

How does infectious tenosynovitis present?

A
  • Present with erythematous fusiform swelling of finger
  • Held in a semiflexed position
  • Tenderness over the length of the tendon sheat and pain with extension of finger are classical
68
Q

How is infectious tenosynovitis treated?

A
  • Empiric antibiotics

- Hand surgeon to review ASAP

69
Q

What are toxin-mediated syndromes due to?

A
  • Superantigens

- Group of pyrogenic exotoxins

70
Q

How do toxin mediated syndrome occur?

A
  • Do not activate immune system via normal contact between APC and T cells
  • Superantigens bypass this and attach directly to the T cell receptors activating up to 20% of the total pool of T cells instead of the normal 1/10,000
  • Massive burst in cytokine release
  • Leads to endothelial leakage, haemodynamic shock, multi-organ failure and ?death
71
Q

What organisms are implicated in toxin-mediated syndromes?

A

Staph aureus

  • TSST1
  • ETA and ETB

Strep pyogenes
-TSST1

72
Q

What can cause toxic shock syndrome?

A
  • Prolonged tampon use

- Staph aureus secreting TSST1 in small skin infections

73
Q

What is the diagnostic criteria for staphylococcal TSS?

A
  • Fever
  • Hypotension
  • Diffuse macular rash
  • Three of the following organs involved:Liver, blood, renal, gatrointestinal, CNS, muscular
  • Isolation of Staph aureus from mucosal or normally sterile sites
  • Production of TSST1 by isolate
  • Development of antibody to toxin during convalescence
74
Q

What is streptococcal TSS associated with?

A

Almost always associated with presence of Streptococci in deep seated infections such as erysipelas or necrotising fasciitis

75
Q

What is the treatment for streptococcal TSS?

A

Treatment necessitates urgent surgical debridement of the infected tissues

76
Q

How does the mortality rate vary between strep and staph TSS?

A
  • Strep 50%

- Staph 5%

77
Q

How is TSS treated?

A
  • Remove offending agent (ex tampon)
  • Intravenous fluids
  • Inotropes
  • Antibiotics
  • Intravenous immunoglobulins
78
Q

What is staphylococcal scalded skin syndrome?

A

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

79
Q

Who is commonly affected by staph scalded skin syndrome?

A

Usually occurs in children but rarely in adults as well

80
Q

How does staph scalded skin syndrome present?

A

Characterised by widespread bullae and skin exfoliation

81
Q

What is the treatment for staph scalded skin syndrome?

A

Treatment with intravenous fluids and antimicrobials

82
Q

What is the mortality rate for staph scalded skin syndrome?

A

Mortality 3% in children but higher in adults who often are immunosuppressed

83
Q

What is Panton-Valentine leucocidin toxin?

A
  • It is a gamma haemolysin

- Can be transferred from one strain of Staph aureus to another, including MRSA

84
Q

What can Panton-Valentine leucocidin toxin cause?

A

SSTI and haemorrhagic pneumonia

85
Q

Who does Panton-Valentine leucocidin toxin tend to affect?

A

Tends to affect children and young adults

86
Q

How does Panton-Valentine leucocidin toxin present?

A

Recurrent boils which are difficult to treat

87
Q

How is Panton-Valentine leucocidin toxin treated?

A

Antibiotics which reduce toxin production

88
Q

What are the 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
89
Q

How do IV catheter associated infections tend to present?

A
  • Normally starts as local SST inflammation progressing to cellulitis and even tissue necrosis
  • Common to have an associated bacteraemia
  • Commonly forms a biofilm which then spills into bloodstream
  • Can seed into other places (ex endocarditis, osteomyelitis)
90
Q

What organisms are commonly implicated in IV catheter associated infections?

A

Staph aureus (MSSA and MRSA)

91
Q

How is a diagnosis of IV catheter associated infections made?

A

Diagnosis made clinically or by positive blood cultures

92
Q

How are IV catheter associated infections managed?

A
  • Treatment is to remove cannula
  • Express any pus from the thrombophlebitis
  • Antibiotics for 14 days
  • Echocardiogram
93
Q

How are IV catheter associated infections prevented?

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
94
Q

How are surgical wounds classified?

A

Class I
-Clean wounds

Class II
-Clean-contaminated wounds

Class III
-Contaminated wound

Class IV
-Infected wound

95
Q

Class I surgical wound

A

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

96
Q

Class II surgical wound

A

Clean-contaminated wound (respiratory, alimentary, genital or infected urinary tracts entered but no unusual contamination)

97
Q

Class III surgical wound

A

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

98
Q

Class IV surgical wound

A

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

99
Q

What organisms can cause surgical site infections?

A
  • Staph aureus (incl MSSA and MRSA)
  • Coagulase negative Staphylococci
  • Enterococcus
  • Escherichia coli
  • Pseudomonas aeruginosa
  • Enterobacter
  • Streptococci
  • Fungi
  • Anaerobes
100
Q

What are the patient-associated risk factors for surgical site infections?

A
  • Diabetes
  • Smoking
  • Obesity
  • Malnutrition
  • Concurrent steroid use
  • Colonisation with Staph aureus
101
Q

What are the procedural associated risk factors fro surgical site infections?

A
  • Shaving of site the night prior to procedure
  • Improper preoperative skin preparation
  • Improper antimicrobial prophylaxis
  • Break in sterile technique
  • Inadequate theatre ventilation
  • Perioperative hypoxia
102
Q

How are surgical site infections diagnosed?

A
  • Importance of sending pus/infected tissue for cultures especially with clean wound infections
  • Avoid superficial swabs – aim for deep structures
  • Consider an unlikely pathogen as a cause if obtained from a sterile site (ex bone infection)
103
Q

How should surgical site infections be treated?

A

Antibiotics to target the likely organism

104
Q

What SST infections require urgent attention?

A
  • Necrotising fasciitis
  • Pyomyositis
  • Toxic shock syndrome
  • PVL infections
  • Venflon-associated infections

Systems: Infection AB (12 decks)

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