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Dermatology > Skin and Soft tissue infections > Flashcards

Skin and Soft tissue infections Flashcards

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Dermatology Board Prep flashcards
1
Q

Cellulitis definition

A

Inflammation of th subcutaenous connective tissue. Bacteria breach the skin barrier and infect and spread throughout the deeper dermis and fat (does not involve fascia/muscle

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2
Q

Clinical features of cellulitis

A
  • classical signs of inflammation (swelling, redness, heat and tenderness)
  • lower extremities
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3
Q

Who is cellulitis most common in?

A

middle age and elderly

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4
Q

Common organisms that cause cellulitis

A

not purluent

  • B haemolytic streptococci (A,C,G)
    • Group B haemolytic streptococci: infants/adults with comorbidities

purlulent cellulitis

  • is staphylococcus aureus

facial ceullitis in children:

  • streptococcus pneumoniae/haemophillus influenzae
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5
Q

Celullitis predisposing risk factors

A
  • Portal of entry
    • Laceration / insect bite / athlete’s foot•
  • Severe disease
    • Elderly / diabetes
  • Recurrent episodes
    • Tinea pedis, lymphoedema, venous insufficiency, pressure ulcers, and obesity•Intravenous drug use / “skin-popping”
  • S. aureus most common cause / polymicrobial
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6
Q

epidemiology of cellulitis

A
  • Streptococcus pyogenes is one of the most frequent pathogens of humans
    • Carriage 5-15%, usually in the respiratory tract and vaginal tract
  • Staphylococcus aureus carried by 30-40% of healthy people
    • Normally nose, moist areas of skin
    • MRSA prevalence approx 2%
  • Immunocompromised
    • Wider range organisms: Gram negative rods / anaerobes / fungi
  • Mycobacterial infection
    • Biopsy: granulomas / mycobacterial culture
  • Children
    • Facial cellulitis: H.influenzae / S.pneumoniae
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7
Q

Management of cellulitis

A
  1. Are they septic? - SIRS criteria
  2. anatomical site - Oribital> (medical and surgical emergency)
  3. Hospital acquired infection
  4. Comoribidity
  5. IV vs Oral hospital vs home
  6. HDU/ICU surgery/clindamycin
  7. MRSA Rx
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8
Q

Who would you admitt to hospital?

A
  • Sepsis syndrome (any 2 of heart rate >100; respiratory rate >20/minute; temperature >38 ̊C or <36 ̊C; white cell count >12 or <4/mm3)
  • Systolic Blood Pressure <100mmHg
  • Severe, localised pain
  • Rapidly evolving skin lesions or skin blistering
  • Confusion
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9
Q

Treatment of celluitis

A
  • Strep pyogenes - non purulent
    • Always sensitive to penicillin
    • amoxcillin - better absorbed
    • flucloxacillin
  • Staph aureus
    • ​Flucloaxillin
    • MRSA = vancomycin
  • Penicillin allergy
    • doxycyline
    • clindamycin - c diff
  • Animal bites- polymicrobial
    • ​broad cover - co-amoxiclav, augmentin
  • fresh water exposure
    • ​penicillin/ciprofloxicin
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10
Q

Differential diagnosis of cellulitis

A
  • Status dermatiis - bilateral with no pain (vellulitis, unilateral with pain)​
  • Arthris- pain on movment of joint
  • drug reactions - usually associated with itch
  • Nec fasc
  • DVT - rule out with doppler
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11
Q

Management of cellulitis

A
  • mark area of inflammation to monitor progress
  • if no progrress, consider
    • inadequate ABx
    • admission to hospital
    • underlying confition
    • incorrect diagnsosis
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12
Q

Erysipelas

A
  • Involves the upper dermis and superficial lymphatics
  • Raised lesions with clear line of demarcation
  • Classically butterfly involvement of the face but now accounts for only about 20% of cases. The legs are affected in up to 80% of cases.
  • This is a clinical diagnosis. Erysipelas is diagnosed based on how the skin looks
  • Infants, young children and older adults
  • Usually group A strep, rarely: B, C, G and Staph aureus
  • Elevated ASO titre 10 days
  • Recurrence in 30% over 3 years

Erysipalas involves the ear and cellulitis does not

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13
Q

Impetigo definition

A

Contagious superficial infection that occurs in two forms:

  • Bullous - s.aureus
  • non bullous - S. aureus, streptococci or both
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14
Q

Clinical features of impetigo

A

Lesions mau occur anywhere on the body

  • non bullous - initial lesion is a small pustule that ruptures to leabe ann extending area of exidatoon and crusting. Crust eventually separate to leabe areas of erythema which fade without scarring
  • Bullous form - large superficial blisters. These rupture and there is exudation and crusting, and teh ctratum corneum peels back at the edges

Honey coloured crust

Affects primarily children or sports persons

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15
Q

Management of impetigo

A
  • remove crust gently
  • fluxcloaxcillin
  • consider if secondary infection of exsisting skin lesions
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16
Q

Pyomysositis

A
  • An acute bacterial infection of skeletal muscle usually caused by Staph aureus
  • The accumulation of pus is initially intra-muscular
  • Blood cultures positive in 5-35% of cases
  • Children in the tropics and adults in the developed world
  • Predisposing factors include IVDA, post-partum or post-abortion, immunosuppression
  • Role for local mechanical injury has been hypothesised
  • S pyogenes (Group A strep) causes 1-5% of cases
  • Drainage and antibiotics
  • Continued fever after drainage may suggest a further undrained focus
17
Q

Bites

A
  • Prophylaxis in certain indications
    • deep bites
    • hand bites
    • splenectomy/ immunocompromise
    • cat bites more infective than dog bites
  • Aggresive debridement and abscess drainage
  • send swab/pus/ blood culures
  • ABx - broad cover (staphy, anaerobes, pasturella)
  • Human bites - blood bourne viruses
18
Q

Pasturella

A
  • gram negative coccobacillus
  • commensual of upper respiratory tract cats and dogs
  • human infection with no animal bite, scratch
  • diabetes and LD susceptible

treatment - Penicillins, tetracyclines, quinolones

19
Q

PVL producing staph aureus

A

•Panton ‐ Valentine Leukocidin (PVL) is a toxin which destroys white blood cells

Carried by <2% of UK Staph aureus isolates, in the UK most of these are MSSA

usually associated with necrotising SSTI but can also cause invasive infections such as fulminant haemorrhagic pneumonia in young previously fit people•Community isolates more likely to carry the toxin than hospitalThe role the toxin has in virulence is unclear

suspect in patients with reccurrent boils/ and those in close contact

20
Q

Cutaneous anthrax

A

Spore forming, grm-positive rod which allows is to exist in environment

Most antrhax cutaenous

Exposure to spore when handling sick animals or contaminated wool, hair

Major features
•Surrounded by extensive oedema
•Painless and non-tender

Minor features
•Progresses over 2-6 days through papular, vesicular and ulcerated stages before development of black eschar
•Most commonly affects hands, forearms, face and neck
•Discharge of serous fluid
•Local erythema and induration
•Local lymphadenopathy
•Associated with systemic malaise including headache, chills and sore throat; but afebrile

21
Q

Treatment of cutaneous anthrax

A

5 drugs

  • penicillin
  • flucloaxcilin
  • clindamycin
  • ciprofloxacin
  • metronidazole
22
Q

Burns

A

Damage to the skin (heat, chemical, radiation) causing protein denaturing

  • Superficial (epidermis only). Painful
  • Partial-thickness (epidermis and dermis). May be painless
  • Full thickness (to subcutaneous tissue). Painless
  • Percentage body surface area affected

Damage to skin compromises resistance to environment
–Infection
–Hypothermia
–Acid base abnormalities
–Dehydration

  • Rapid bacterial colonisation, but infection must be diagnosed clinically
  • Swabs of burns rarely sterile - interpretation of results needs clinical judgement
  • Involve Plastic Surgeons and Microbiology teams early
23
Q

Management of infected burns

A

•Management of infected burns may involve:
–Occlusive dressings
–Topical antimicrobials e.g. silver sulfadiazine, may delay re-epithelialisation, chlorhexidine, bacitracin
–Systemic antibiotics, (directed by culture results), required in invasive infection.–Evidence base for comparison of individual agents poor.

24
Q

Herpes simplex virus

A

–Primary infection asymptomatic 60%
–HSV-1: orofacial disease / “cold sore”
–Type-2: genital herpes
–Vesicular, may be painful
–Recurrent: virus latent in sensory nerve ganglia
–Diagnosis: clinical. Blood or vesicle fluid for PCR Serology sometimes helpful
–Treatment: aciclovir (topical, oral, IV)

25
Q

Varcicella zoster

A
  • Fever / widespread vesicular rash
  • Often a self limiting childhood infection
  • Highly transmissible via contact, droplet and airborne routes (nurse id side room if hospitalised)
  • Contagious from 1-2 days before rash develops until vesicles crust over
  • Diagnosed by PCR of vesicle fluid (or serology)
  • Risks to foetus and neonate
  • More serious in adults, especially pregnant women and smokers: fulminating varicella pneumonia
  • Treat adults within 48hours of rash: Aciclovir PO/IV or Valaciclovir PO for 7 days
26
Q
A
27
Q

3 main types of skin infections

A
  • Bacterial ( staphylococcus, streptococcal)
  • viral (HPV, HSV)
  • Herpes zoster
  • fungal (tinea)
  • Candida
  • Infestations e,g scabies

Dermatology (10 decks)

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