Skin and Soft Tissue Flashcards

1
Q

What causes impetigo?

A

Most commonly S. Aureus, less commonly S. pyogenes

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2
Q

Describe impetigo

A

Superficial skin infection

Multiple vesicular lesions on erythematous base

Golden crust highly suggestive

Common 2-5yo, highly infectious

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3
Q

What are predisposing factors to impetigo?

A
  • skin abrasions
  • minor trauma
  • burns
  • poor hygiene
  • insect bites
  • chicken pox
  • eczema
  • atopic dermatitis
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4
Q

Describe treatment of impetigo

A

Small areas treated with topical abs alone

Large areas both topical and oral abs (flucloxacillin)

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5
Q

Describe erysipelas

A

Infection of upper dermis, painful, red area (no central clearing)

Associated fever

Regional lymphadenopathy and lymphangitis

Typically distinct elevated borders

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6
Q

What causes erysipelas?

A

most commonly S pyogenes

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7
Q

Where does erysipelas tend to occur?

A

Areas of pre-existing lymphoedema, venous stasis, obesity, paraparesis, diabetes mellitus

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8
Q

Describe cellulitis

A

Diffuse skin infection involving deep dermis and subcutaneous fat

Presents as a spreading erythematous area with no distinct borders

Fever is common, regional lymphadenopathy and lymphangitis

Possible source of bacteraemia

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9
Q

What causes cellulitis?

A

Most likely organisms are S.Pyogenes and S.Aureus

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10
Q

What are predisposing factors to cellulitis?

A

Diabetes mellitus
Tinea pedis
Lymphoedema

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11
Q

What is the treatment of erysipelas and cellulitis?

A

A combination of anti-staphylococcal and anti-streptococcal abs

In extensive disease, admission for IV Abs and rest

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12
Q

What are some hair associated infections?

A

Folliculitis
Furunculosis
Carbuncles

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13
Q

What is a folliculitis?

A

erythema and pustule in a single follicle

up to 5mm in diameter

present as small red papules

typically found on head, back, buttocks and extremities

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14
Q

What is a furuncle?

A

red, tender nodule surrounding a follicle with one draining point

Commonly “boils”, extending into dermis and subcutaenous tissue
Usually affects moist, hairy, friction-prone areas

Systemic symptoms uncommon

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15
Q

What are carbuncles?

A

Deep follicular abscesses of several follicles with several drainage points

Often back of neck, posterior trunk or thigh

Multiseptated abscesses, purulated material may be expressed from multiple sites

Constitutional symptoms common

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16
Q

What causes folliculitis and furunculosis?

A

Staph aureus most common

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17
Q

What are risk factors for furunculosis?

A

Obesity, diabetes mellitus, chronic kidney disease, corticosteroid use

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18
Q

How do you treat hair-associated infections?

A

Folliculitis; no treatment or topical abs

Furunculosis; no treatment or topical abs. If not improving oral abs may be req

Carbuncles; often require admission, surgery and IV Abs

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19
Q

Describe necrotising fasciitis

A

An infectious disease emergency

Any site may be affected

Rapid onset

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20
Q

What are predisposing conditions for necrotising fasciitis?

A
Diabetes mellitus
Surgery
Trauma
Peripheral vascualr disease
Skin popping
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21
Q

What is type I necrotising fasciitis?

A

Refers to mixed aerobic and anaerobic infection

Typical organisms

  • strep
  • staph
  • enterococci
  • gram -ve bacilli
  • clostridium
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22
Q

What is type II necrotising fasciitis?

A

Monomicrobial

Normally associated with S Pyogenes

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23
Q

How does necrotising fasciitis develop?

A

Erythema
Extensive oedema
Severe, unremitting pain

Haemorrhagic bullae, skin necrosis and crepitus may develop

Systemic features include; fever, hypotension, tachycardia, delirium, multiorgan failure

Anaesthesia at site of infection is highly suggestive of this disease

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24
Q

How is necrotising fasciitis treated?

A

Surgical review mandatory

Abs should be broad spectrum

  • flucloxacillin
  • gentamicin
  • clindamycin

overall mortality between 17-40%

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25
Describe pyomyositis
Purulent infection deep within striated muscle, often manifesting as abscess infection often secondary to seeding into damaged muscle
26
What are common sites of pyomyositis?
- thigh - calf - arms - gluteal region - chest wall - psoas muscle
27
How does pyomyositis present?
Fever, pain, woody induration of affected muscle if untreated can lead to septic shock and death
28
what are predisposing factors to pyomyositis?
- diabetes mellitus - HIV/immunocompromised - IV drug use - rheumatological diseases - malignancy - Liver cirrhosis
29
What causes pyomyositis?
Most commonly S. Aureus other organisms can be involved including gram positives and negatives, TB and fungi
30
How do you investigate pyomyositis?
CT/MRI
31
What is the treatment of pyomyositis?
Drainage with antibiotics cover depending on gram stain and culture results
32
Describe septic bursitis
Infection most common from adjacent skin infection Peribursal cellulitis, swelling and warmth are common Fever and pain on movement
33
What is a bursa?
Small sac-like cavities containing fluid, located subcutaneously between bony prominences and tendons Facilitate movement with reduced friction Most common are patellar and olecranon
34
What are predisposing factors to septic bursitis?
- rheumatoid arthritis - alcoholism - diabetes mellitus - IV drug abuse - immunosuppression - renal insufficiency
35
How is septic bursitits diagnosed?
Based on aspiration of the fluid
36
What causes septic bursitis?
Most common cause is S.Aureus Rarer organisms include - gram negatives - mycobacteria - brucella
37
Describe infectious tenosynovitis
Infection of synovial sheets that surround tendons Penetrating trauma most common inciting event Present with erythemtous fusiform swelling or finger, held in a semi-flexed position Tender over length of tendon sheet and pain on extension
38
What causes infectious tenosynovitis?
Most common cause S.aureus and streptococci Chronic infections due to mycobacteria, fungi Possibility of disseminated gonococcal infection
39
Management of infectious tenosynovitis
- Empirical Abs | - Hand surgeon review ASAP
40
Describe toxin-mediated syndromes
Often due to super-antigens Group of pyrogenic exotoxins Do not activate immune system via normal contact between APC and T cells Superantigens bypass this and attach directly to T cell receptors Massive cytokine release Endothelial leakage, haemodynamic shock, multi-organ failure, ?death
41
What causes toxin mediated syndromes?
Most commonly due to some strains of S.Aureus (TSST, ETA and ETB) and S.Pyogenes (TSST1)
42
What are diagnostic criteria for staph toxic shock syndrome?
Fever, hypotension, diffuse macular rash three of the following organs - liver, blood, renal, GI, CNS, muscular Isolation of S.Aureus from mucosal or normally sterile sites Development of antibody to toxin
43
Describe strep TSS
Almost always associated w/ strep presence in deep seated infections Mortality rate much higher than in staph Treatment = urgent surgical debridement of infected tissues
44
Describe treatment of TSS
Remove offending agent (ex tampon) IV fluids Inotropes ABs IV Igs
45
Describe staph scalded skin syndrome
Infection due to particular strain of S.Aureus producing exfoliative toxin A or B Widespread bullae and skin exfoliation Usually children
46
How do you treat Staph scalded skin syndrome?
IV fluids and antimicrobials
47
Describe panton-valentine leucocidin toxin
Gamma-haemolysin Can be transferred from one S.Aureus strain to another (incl MRSA) Can cause SSTI and haemorrhagic pneumonia Present with recurrent boils, difficult to treat
48
How do you treat panton-valentine leucocidin toxin?
ABs that reduce toxin production
49
What are risk factors for IV catheter associated infections?
- continuous infusion >24hours - cannula in situ >72hours - cannula in lower limb - patients with neurological/neurosurgical problems
50
How do IV catheter associated infections progress?
Normally starts as local SST inflammation progressing to cellulitis and even tissue necrosis
51
What causes IV catheter associated infections?
Most commonly S.Aureus (MSSA and MRSA) Commonly forms biofilm which then spills into bloodstream
52
What is the treatment for IV catheter associated infections?
Remove cannula Express any pus from thrombophlebitis ABs for 14 days Echocardiogram PREVENTION MORE IMPORTANT; don't leave unused cannula, don't insert unless using, change cannulae every 72hours, use aseptic technique when inserting
53
How are surgical wounds classified?
Class I - IV
54
What is a class I surgical wound?
Clean wound (resp, alimentary, genital or infected urinary systems not entered)
55
What is a class II surgical wound?
Clean-contaminated wound (resp, alimentary, genital or urinary tracts entered but no usual contamination)
56
What is a class III surgical wound?
Contaminated wound (open, fresh accidental wounds or gross spillage from GIT)
57
What is a class IV surgical wound?
Infected wound (existing clinical infection, infection present prior to operation)
58
What causes surgical site infections?
- S.Aureus - coagulase negative Staph - enterococcus - E. Col - pseudomonas aeruginosa - enterobacter - strep - fungi - anaerobes
59
What are patient associated risk factors for surgical site infections?
- diabetes - smoking - obesity - malnutrition - concurrent steroid use - colonisation w/S.Aureus
60
What are procedural risk factors for surgical site infections?
- shaving of site - improper peroperative skin prep - improper antimicrobial prophylaxis - break in sterile technique - inadequate theatre ventilation - perioperative hypoxia
61
How do you diagnose surgical site infections?
Send pus/infected tissue for cultures Avoid superficial swabs; aim for deep structures Consider an unlikely pathogen as a cause if obtained from a sterile site
62
Treatment of surgical site infections
Antibiotics to target likely organisms