Skin and Soft Tissue Infections Flashcards

1
Q

What is the presentation of impetigo?

A

GOLDEN CRUST
Multiple vesicular lesions on erythematous base
Tends to be face, limbs
Children 2-5y

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2
Q

Where is impetigo an infection of?

A

Upper epidermis

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3
Q

What bacteria tend to cause impetigo?

A

Staph aureus (less commonly strep pyogenes)

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4
Q

What factors predispose to impetigo infection?

A

Broken skin basically

Skin abrasions, minor trauma, burns, poor hygiene, insect bites, chickenpox, eczema, atopic dermatitis

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5
Q

How do you treat impetigo?

A

Flucloxacillin

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6
Q

Where is erysipelas an infection of?

A

Upper dermis

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7
Q

What does erysipelas present like?

A

Pain, red area + fever + regional lymphadenopathy+ lymphangitis
ELEVATED BORDERS
Tends to be lower limbs

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8
Q

What tends to cause erysipelas?

A

Strep pyogenes

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9
Q

What can predispose to erysipelas?

A

Pre-existing lymphoedema, venous stasis, obesity, paraparesis, DM

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10
Q

Why is there high recurrence of erysipelas?

A

There is damage to the lymphatic system which never returns to its original function

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11
Q

Where does cellulitis affect?

A

Deep dermis and s/c fat

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12
Q

What does cellulitis present like?

A

Erythematous area with no distinct borders + fever + regional lymphadenopathy + lymphangitis (inflammation of lymphatic system)

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13
Q

What organism causes cellulitis most likely?

A

Strep pyogenes and staph aureus

Gram -ve infections in febrile neutropenia and DM

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14
Q

How might someone have ended up with cellulitis?

A

Portals of entry to skin (e.g. fungal foot infection) or infection secondary to systemic infection

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15
Q

What is the appearance of lymphangitis?

A

Red lines along line of lymphatic vessels

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16
Q

What conditions predispose to cellulitis?

A

DM, tinea pedis, lymphoedema

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17
Q

How do you treat erysipelas and cellulitis?

A

Flucloxacillin & benzyl penicillin (others: vancomycin/teicoplanin)
IV in extensive dx

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18
Q

What is folliculitis?

A

Circumscribed, pustular infection of a hair follicle

Up to 5mm

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19
Q

What does folliculitis present like?

A

Small red papules with central area of purulence that may rupture and drain

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20
Q

What typically causes folliculitis?

A

Staph aureus

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21
Q

What are furnucles?

A

Boils

Single hair follicle-associated inflammatory nodule (infection spreads into dermis and forms an abscess in s/c tissue)

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22
Q

Where do furnucles tend to occur?

A

Moist, hairy, friction prone areas (face, axilla, neck, buttocks)

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23
Q

What tends to cause furnucles?

A

Staph aureus

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24
Q

What are the risk factors for furnucles?

A

Obesity, DM, atopic dermatitis, CKD, corticosteroid use, shaving/waxing

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25
Q

What are carbuncles?

A

When infection extends to involve multiple furnucles
Multiseptated abscesses
+ high temp, low BP, signs and symptoms of sepsis

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26
Q

What does having a carbuncle normally mean?

A

Patient is immunocompromised

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27
Q

How do you treat carbuncles?

A

Systemic antibiotics

May req. surgery and admission to hospital

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28
Q

What is necrotising fasciitis?

A

Rapidly progressive infection resulting in extensive necrosis of deep tissue (s/c tissue, fascia, muscle) & systemic infection that can become lifethreatening

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29
Q

What can predispose to necrotising fasciitis?

A

DM, surgery, skin popping (IVDA into s/c fat), trauma, peripheral vascular disease

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30
Q

What are the two types of necrotising fasciitis?

A

Type 1 - mixed aerobic and anaerobic (diabetic foot infection, Fournier’s gangrene)
Type 2 - monomicrobial (strep pyogenes usually)

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31
Q

What are the typical organisms involved in type 1 necrotising fasciitis?

A

Strep, staph, enterococci, gram -ve bacilli, clostridium

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32
Q

What are the clinical features of necrotising fasciitis?

A

Rapid onset
Development of erythema, extensive oedema, severe, unremitting pain
Anaesthesia at site of injury
Haemorrhagic bullae, skin necrosis, crepitus
Systemic features: fever, hypotension, tachycardia, delirium, multi-organ failure

33
Q

What can necrotising fasciitis progress to?

A

Gangrene, amputations, fatality

34
Q

How do you treat necrotising fasciitis?

A

Surgical review
Broad spectrum antibiotics - flucloxacillin, gentamicin, clindamycin, benzyl penicillin & metronidazole)
Rx for sepsis

35
Q

What is pyomyositis?

A

Purulent infection deep within striated muscle, often manifesting as pus filled absncess

36
Q

What is pyomyositis secondary to?

A

Seeding into damaged muscle (i.e. infection is elsewhere and spreads via bloodstream to muscle)

37
Q

Where are common sites for pyomyositis?

A

Thigh, calf, arms, gluteal region, chest wall, psoas

38
Q

What is the presentation for pyomyositis?

A

Fever, pain, woody induration of affected muscle

can lead to septic shock and death

39
Q

What predisposes to pyomyositis?

A

DM, HIV, immunocomp, IVDA, rheumatological dx, malignancy, liver cirrhosis

40
Q

What organism tends to cause pyomyositis?

A

Staph aureus

Others: TB/fungi

41
Q

How do you investigate pyomyositis?

A

CT/MRI

42
Q

How do you Rx pyomyositis?

A

Drainage & antibiotics depending on gram stain and culture result

43
Q

Where is septic bursitis most common?

A

Patellar and olecranon

44
Q

How does septic bursitis tend to occur?

A

From adjacent skin infection

45
Q

What factors predispose to septic bursitis?

A

RA, alcoholism, DM, IVDA, immunosuppression, renal insufficiency

46
Q

What is the presentation of septic bursitis?

A
Area of redness over joint
Loses definition around joint 
Peribursal cellulitis, swelling, war 
Fever 
Pain on movement
47
Q

How do you differentiate septic bursitis from septic arthritis?

A

In septic arthritis unable to flex and extend the joint

48
Q

How do you diagnose septic bursitis?

A

Aspiration of fluid

49
Q

What organism tends to cause septic bursitis?

A

Staph aureus

Others: gram -ves, mycobacteria, Brucella

50
Q

What is infectious tenosynovitis?

A

Infection of synovial sheaths surrounding the tendon

51
Q

What tendons are most commonly involved in infectious tenosynovitis?

A

Flexor muscle assoc tendons & tendon sheaths of hands most commonly injured

52
Q

What tends to be the initiating event in infectious tenosynovitis?

A

Penetrating trauma

53
Q

What organisms most commonly cause infectious tenosynovitis?

A

Staph aureus and strep
Chronic infections due to mycobacteria and fungi
Rare cause: disseminated gonorrhoea infection

54
Q

What is the presentation of infectious tenosynovitis?

A
Erythematous fusiform (tapers at both ends) swelling of finger
Held in semi-flexed position (least amount of pain) 
Tenderness over length of tendon sheath and pain with extension of finger are classical
55
Q

How do you treat infectious tenosynovitis?

A

Empirical antibx

Referral to hand surgeon

56
Q

What is the pathophysiology behind toxin mediated syndromes?

A

Due to superantigens
Group of pyrogenic exotoxins
Do not activate immune system via normal contact between APC cells and T cells

Superantigens bypass this and attach directly to T cell receptors –> huge activation of T cells –> massive cytokine release –> endothelial leakage, haemodynamic shock, multiorgan failure & sometimes death

57
Q

What are the strains that can cause toxin mediate syndromes?

A

Staph aureus: TSST1, ETA and ETB

Strep pyogenes: TSST1

58
Q

Define toxic shock syndrome

A

Systemic inflammatory reaction caused by bacterial exotoxins

59
Q

What can cause toxic shock syndrome?

A

E.g. tampon use, small skin infections due to staph aureus secreting TSST1

60
Q

What is the diagnostic criteria for Staphylococcal TTS?

A

Fever, hypotension, diffuse macular rash (pink, blanching, all over body)
Three of liver, blood, renal, GI, CNS, muscular systems involved
Isolation of staph aureus from normally sterile sties
Production of TSST1 from isolate
Development of antibody to toxin during convalescence

61
Q

What is streptococcal TTS always associated with?

A

Presence of streptococci in deep seated infections, e.g. NF/erysipelas

62
Q

How do you treat streptococcal TTS?

A

Urgent surgical debridement of infected tissues

Mortality much higher than for staph TTS!!

63
Q

How do you Rx TSS?

A
Remove offending agent, e.g. tampon 
IV fluids
Inotropes
Antibiotics 
IV Ig
64
Q

What causes staphylococcal scalded skin syndrome?

A

Staph aureus producing the exfoliative A or B toxin

65
Q

What is staphylococcal scalded skin syndrome characterised by?

A

Widespread bullae and skin exfoliation

66
Q

How do you treat SSS?

A

IV fluids and antibiotics

67
Q

What is Panton-Valentine Leucoidin toxin?

A

Toxin produced by some strains of staph aureus (gamma haemolysin that can be transferred from one strain of staph aureus to another)

68
Q

What does PVL toxin cause?

A

Skin and soft tissue infections and haemorrhagic pneumonia

Patients present with recurrent boils which are difficult to treat

69
Q

What are IV-catheter associated infections often presenting like?

A

Local skin and soft tissue inflammation, but may progress to cellulitis and even tissue necrosis
Common to have assoc. bacteraemia

70
Q

What are risk factors for IV-catheter associated infections?

A

Continuous infusion >24h
Cannula in situ >72h
Cannula in lower limb
Patients with neurological/neurosurgical problems

71
Q

What bacteria tends to cause IV catheter assoc. infections?

A
Staph aureus (MSSA/MRSA)
 Commonly forms biofilm
72
Q

How do you diagnose IV catheter assoc. infections?

A

+ve blood cultures or clinical diagnosis

73
Q

What are the presentations of IV catheter assoc. infections?

A

Area of thrombophlebitis going up
Veins feel really hard
Assoc. fever

74
Q

How do you Rx IV catheter assoc. infections?

A

Remove cannula
Express any pus from thrombophlebitis
Antibx for 14 days
ECG

75
Q

How can you prevent IV catheter assoc. infections?

A
Do not leave in unused cannulas
Do not insert cannula unless req. 
Change cannula every 72h
Monitor for thrombophlebitis
Use aseptic technique when inserting cannula
76
Q

What is the classification of surgical site infections?

A

1 - clean wound (resp, alimentary, genital, urinary systems not entered)
2 - clean wound (above tracts entered but no unusual contamination) 3 - contaminated wound (open, fresh, aciidental wounds or gross spillage from GI tract)
4 - infected wound (existing clinical infection, infection present before op)

77
Q

What can cause surgical site infections?

A
Staph aureus (MSSA/MRSA)
Coagulase -ve staph
Enterococcus 
E. coli
Pseudomonas aeruginosa
Enterobacter
Strep 
Fungi 
Anaerobes
78
Q

What are risk factors for surgical site infections?

A
Diabetes
Smoking
Obesity
Malnutrition 
Steroid use 
Colonisation with staph aureus 
Shaving of site prior to procedure
Improper prep of skin preoperatively
Improper antimicrobial prophylaxis
Break in sterile technique 
Inadequate theatre ventilation 
perioperative hypoxia
79
Q

How do you diagnose surgical site infections?

A

Sending pus/infected tissue for cultures
Avoid superficial swabs
Consider unlikely pathogen as cause if obtained from sterile site