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Infection > Skin and Soft Tissue > Flashcards

Skin and Soft Tissue Flashcards

1
Q

What are the skin compartments?

A

Epidermis, dermis, subcutaneous fat, fascia and muscle

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2
Q

What are the infection sites of the skin?

A

Impetigo - epidermis
Folliculitis - hair follicle
Erysipelas - deeper in skin

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3
Q

What are things to consider about the host?

A

Diabetes leading to neuropathy and vasculopathy
Immunosuppression
Renal failure
Milroy’s disease - lymphoedema of lower limbs
Predisposing skin conditions

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4
Q

Describe impetigo

A

Superficial skin infection
Multiple vesicular lesions on erythematous base
Golden crust is highly suggestive of diagnosis
Highly infectious

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5
Q

What most commonly causes impetigo?

A

Staph. aureus
Less common - strep pyogenes

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6
Q

What are predisposing factors for impetigo?

A

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

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7
Q

Where does impetigo mainly occur?

A

Exposed parts of body including face, extremities and scalp
Common in children 2-5 years

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8
Q

What is the treatment for impetigo?

A

Small areas can be treated with topical antibiotics alone
Large need topical treatment and oral antibiotics - flucloxacillin

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9
Q

Describe erysipelas

A

Infection of the upper dermis
Painful, red area with associated fever
Regional lymphadenopathy and lymphangitis
Distinct elevated borders
High recurrence rate

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10
Q

What is erysipelas most commonly due to?

A

Strep pyogenes

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11
Q

Where does erysipelas mainly involve?

A

70-80% of cases involve lower limbs and 5-20% effect face
Tends to occur in areas of pre-existing lymphoedema, venous stasis, obesity, paraparesis and DM

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12
Q

Describe cellulitis

A

Diffuse skin infection involving deep dermis and subcutaneous fat
Presents as spreading erythematous area with no distinct borders
Fever is common
Regional lymphadenopathy and lymphangitis
Possible source of bacteraemia

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13
Q

What is cellulitis most commonly due to?

A

Strep pyogenes and staph aureus
Gram negatives in diabetics and febrile neutropenic

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14
Q

What are some predisposing factors of cellulitis?

A

DM, tinea pedis (athletes foot) and lymphoedema
Patients can have lymphangitis and/ or lymphadenitis

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15
Q

What is the treatment for erysipelas and cellulitis?

A

Combination of anti-staphylococcal and anti-streptococcal antibiotics
In extensive disease - admission for IV antibiotics and rest

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16
Q

What are some hair assocated infections?

A

Folliculitis, furunculosis and carbuncles

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17
Q

Describe folliculitis

A

Circumscribed, pustular infection of a hair follicle
Up to 5mm in diameter
Present as small red papules
Central areas of purulence that may rupture and drain
Constitutional symptoms not often seen

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18
Q

Where is folliculitis mainly found?

A

Head, back, buttocks and extremities

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19
Q

What is the most common organism causing folliculitis?

A

Staph aureus
Benign condition

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20
Q

Describe furunculosis

A

Referred as boils
Single hair follicle associated inflammatory nodule extending into dermis and subcutaneous tissue
Usually affected moist, hairy, friction prone areas of skin
May spontaneously drain purulent material

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21
Q

What are the risk factors and causes for furunculosis?

A

Obesity, DM, atopic dermatitis, chronic kidney disease and corticosteroid use
Staph aureus

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22
Q

Describe carbuncle

A

Occurs when infection spreads to involve multiple furuncles
Multiseptated abscesses and purulent material may be expressed from multiple sites
Constitutional symptoms common
Neck, posterior trunk or thigh

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23
Q

What is the treatment of hair associated infections?

A

Folliculitis - no treatment or topical antibiotics
Furunculosis - no treatment. If not improving then oral antibiotics
Carbuncles - hospital admission, surgery and IV antibiotics

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24
Q

What are predisposing conditions for necrotising fasciitis?

A

DM, surgery, trauma, peripheral vascular disease and skin popping

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25
Q

What is type I necrotising fasciitis?

A

Refers to mixed aerobic and anaerobic infection
Typical organism - strep, staph, enterococci, gram negative bacilli and clostridium

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26
Q

What is type II necrotising fasciitis?

A

Monomicrobial
Normally associated with strep pyogenes

27
Q

Describe necrotising fasciitis

A

Rapid onset
Anaesthesia at site of infection is highly suggestive
Systemic features - fever, hypotension, tachycardia, delirium and multiorgan failure

28
Q

What does necrotising fasciitis present as?

A

Sequential development of erythema, extensive oedema and severe and unremitting pain
Haemorrhagic bullae, skin necrosis and crepitus

29
Q

What is the treatment for necrotising fasciitis?

A

Flucloxacillin, gentamicin and clindamycin - broad spectrum antibiotic
Mortality between 17-40%

30
Q

Describe pyomyositis

A

Purulent infection deep within striated muscle, often manifesting as abscess
Infection is secondary to seeding into damaged muscle
Common sites - thigh, calf, arms, gluteal region, chest wall and psoas muscle

31
Q

How does pyomyositis present?

A

Fever, pain and woody induration of affected muscle
If untreated can lead to septic shock and death

32
Q

What ae predisposing factors for pyomyositis?

A

DM, HIV/ immunocompromised, IV drug use, rheumatological disease, malignancy and liver cirrhosis

33
Q

What is the commonest cause of pyomyositis?

A

Staph aureus
Others include gram positive/ negative, TB and fungi

34
Q

What is the investigation and treatment for pyomyositis?

A

CT/ MRI
Drainage with antibiotic cover on gram stain and culture results

35
Q

Describe septic bursitis

A

Small sac like cavities that contain fluid and lined by synovial membrane
Located subcutaneously between bony prominences or tendons
Facilitate movement with reduced friction
Patellar and olecranon

36
Q

What are predisposing factors for septic bursitis?

A

Rheumatoid arthritis, alcoholism, DM, IV drug abuse, immunosuppression and renal insufficiency
Infection is often from adjacent skin infection

37
Q

How does septic bursitis present?

A

Peri bursal cellulitis, swelling and warmth
Fever and pain on movement
Diagnosed by aspiration of fluid

38
Q

What is the most common cause of septic bursitis?

A

Staph aureus
Rarer - gram negative, mycobacteria and brucella

39
Q

Describe infectious tenosynovitis

A

Infection of synovial sheets that surround tendons
Flexor associated tendons and tendon sheets of hand most common
Penetrating trauma is most common inciting event

40
Q

What is the most common cause for infectious tenosynovitis?

A

Staph aureus and streptococci
Chronic infections may be due to mycobacteria and fungi
Possibly disseminated gonococcal infection

41
Q

How does infectious tenosynovitis present?

A

Erythematous fusiform swelling of finger
Held in semi-flexed position
Tenderness over length of tendon sheat and pain with extension of finger is classical

42
Q

What is the treatment for infectious tenosynovitis?

A

Empiric antibiotics
Hand surgeon to review ASAP

43
Q

Describe toxin-mediated syndromes

A

Group of pyrogenic exotoxins
Do not activate immune system via normal contact between APC and T cells
Super antigens bypass this and attach directly to T cell receptors activating them
Massive cytokine release - endothelial leakage, haemodynamic shock and multiple organ failure

44
Q

What is toxin-mediated syndromes mainly caused by?

A

Staphylococcus aureus and streptococcus pyogenes
S. aureus - TSST1, ETA and ETB
S. pyogenes - TSST1

45
Q

What can cause toxic shock syndrome?

A

High absorbency tampons during menses
Staph aureus secreting TSST1 small skin infections

46
Q

What is the diagnosis criteria for staphylococcal TSS?

A

Fever, hypotension, diffuse macular rash, 3 organs involved - liver, blood, renal, GI, CNS and muscular, isolation of S. aureus from mucosal or normal sterile sites, production of TSST1 by isolate and development of antibody to toxin

47
Q

What is the treatment for streptococcal TSS?

A

Urgent surgical debridement of infected tissues
Mortality higher then staph

48
Q

What is streptococcal TSS associated with?

A

Presence of streptococci in deep seated infections such as erysipelas or necrotising fasciitis

49
Q

What is the treatment for TSS?

A

Remove offending agent, IV fluids, inotropes, antibiotics and IV immunoglobulins

50
Q

Describe staphylococcal scalded skin syndrome

A

Infection due to particular strain of S. aureus producing toxin A or B
Characterised by widespread bullae and skin exfoliation
Usually occurs in children but rarely in adults

51
Q

What is the treatment for staphylococcal scalded skin syndrome?

A

IV fluids and antimicrobials
Mortality is 3% in children but higher in adults who are immunocompromised

52
Q

Describe Panton-Valentine leucocidin toxin

A

Gamma haemolysin
Transferred from one strain of S. aureus to another including MRSA
Can cause SSTI and haemorrhagic pneumonia
Tends to affect children and young adults
Recurrent boils which are difficult to treat

53
Q

What is the treatment for Panton-Valentine leucocidin toxin?

A

Antibiotics that reduce toxin production

54
Q

Describe IV catheter associated infections

A

Nosocomial infection
Normally starts as local SST inflammation progressing to cellulitis and tissue necrosis
Common to have associated bacteraemia

55
Q

What are the risks for IV catheter associated infection?

A

Continuous infusion over more than 24hrs
Cannula in situ for more than 24hrs
Cannula in lower limb
Patients with neurological/ neurosurgical problems

56
Q

What is the main cause of IV catheter associated infection and how is it diagnosed?

A

Staph aureus
Commonly forms a biofilm which then spills into bloodstream and can seed to other places
Diagnosis - clinically or positive blood cultures

57
Q

What is the treatment for IV catheter associated infection?

A

Remove cannula and express any pus from thrombophlebitis
Antibiotics for 14 days
Echo
Prevention is most important

58
Q

What is the classification of surgical wounds?

A

Class 1 - clean wound
Class 2 - clean contaminated wound
Class 3 - contaminated wound
Class 4 - infected wound

59
Q

What are some causes for surgical site infections?

A

Staph. aureus, coagulase negative staphylococci, enterococcus, Escherichia coli, pseudomonas aeruginosa, Enterobacter, streptococci, fungi and anaerobes

60
Q

What are the risk factors for surgical site infection?

A

Diabetes, smoking, obesity, malnutrition, concurrent steroid use and colonisation with staph. aureus

61
Q

What are procedural factors for surgical site infections?

A

Shaving of site the night prior
Improper preoperative skin prep
Improper antimicrobial prophylaxis
Break in sterile technique
Inadequate theatre ventilation
Perioperative hypoxia

62
Q

What is the investigations and treatment for surgical site infections?

A

Importance of sending pus/ infected tissue for culture
Avoid superficial swabs and aim for deep structures
Antibiotic to target likely organism

63
Q

What infections need urgent attention?

A

Necrotising fasciitis, pyomyositis, TSS, PVL infections and Venflon associated infections

Infection (13 decks)

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