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Y4 Lecture Day III > Cutaneous infection & infestation (1) > Flashcards

Cutaneous infection & infestation (1) Flashcards

1
Q

What are commensal bacteria on the skin?

Give examples

A

Commensal bacteria → present on the skin but not causing a disease

  • staphylococci
  • micrococci
  • corynebacteria
  • propionibacteria
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2
Q

Is Staphylococcus Aureus pathogenic or commensal?

A

Staph Aureus

  • always regarded as pathogenic
  • may be commensal
  • disease associated with: direct invasion of the epidermis, hair follicle, production of toxin
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3
Q

Is Streptococcus Pyogens pathogenic or commensal?

A

Streptococcus Pyogens

  • group A streptococcus
  • always pathogenic
  • acute onset and rapid spread
  • may co-infect with staphylococcus
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4
Q

Spot diagnosis

A

Impetigo

  • a superficial bacterial skin infection usually caused by either Staphylcoccus aureus or Streptococcus pyogenes
  • It can be a primary infection or a complication of an existing skin condition such as eczema (in this case), scabies or insect bites
  • common in children, particularly during warm weather
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5
Q

Location of the lesions in impetigo

A

The infection can develop anywhere on the body but lesions tend to occur on the face, flexures and limbs not covered by clothing

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6
Q

Spread of impetigo

A

Spread is:

  • by direct contact with discharges from the scabs of an infected person
  • The bacteria invade skin through minor abrasions and then spread to other sites by scratching
  • Infection is spread mainly by the hands, but indirect spread via toys, clothing, equipment and the environment may occur
  • incubation period is between 4 to 10 days
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7
Q

Spot diagnosis

A

Impetigo

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8
Q

Features of impetigo

A
  • ‘golden’, crusted skin lesions typically found around the mouth
  • very contagious
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9
Q

Management of impetigo

A

Limited, localised disease

  • topical fusidic acid is first-line
  • topical retapamulin is used second-line if fusidic acid has been ineffective or is not tolerated
  • MRSA is not susceptible to either fusidic acid or retapamulin. Topical mupirocin (Bactroban) should, therefore, be used in this situation

Extensive disease

  • oral flucloxacillin
  • oral erythromycin if penicillin-allergic
  • children should be excluded from school until the lesions are crusted and healed or 48 hours after commencing antibiotic treatment
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10
Q

Antibiotics to cover streptococcus and staphylococcus

A
  • Penicillins: Flucloxacillin
  • macrolides: erythromycin, clarithromycin
  • Trimethoprim
  • Tetracycline
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11
Q

Sore, itchy arms

Diagnosis?

A

Impentigenous eczema

(infected eczema with impetigo)

  • Treat eczema + infection together
  • Treat with steroids + antibiotics (Flucloxacillin)
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12
Q

Spot diagnosis

A

Folliculitis

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13
Q

Spot diagnosis

A

Folliculitis

  • due to staph aureus
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14
Q

Management of folliculitis

A

Management:

  • Short course: Flucloxacillin or clarithromycin
  • Chronic: longer course (3-months) of tetracycline antibiotics e.g. doxycycline, lymecycline
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15
Q

Spot diagnosis

A

Ecthyma

  • a skin infection → stapho-strep
  • crusted sores beneath which ulcers form
  • it’s a deep form of impetigo, as the same bacteria causing the infection are involved

Management: 3-weeks of clarithromycin

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16
Q

Spot diagnosis

A

Ecthyma

(staph-strep infection)

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17
Q

Spot diagnosis

A

Cellulitis

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18
Q

What’s cellulitis? (pathophysiology)

A

Cellulitis is a term used to describe an inflammation of the skin and subcutaneous tissues, typically due to infection by Streptococcus pyogenes or Staphylcoccus aureus.

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19
Q

Features of cellulitis

A
  • commonly occurs on the shins
  • erythema, pain, swelling
  • there may be some associated systemic upset such as fever
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20
Q

Criteria for admission of a patient with cellulitis

A

Eron classification → to guide who needs to be admitted

Admit for IV antibiotics the following patients:

  • Has Eron Class III or Class IV cellulitis
  • Has severe or rapidly deteriorating cellulitis (for example extensive areas of skin)
  • Is very young (under 1 year of age) or frail
  • Is immunocompromized
  • Has significant lymphoedema
  • Has facial cellulitis (unless very mild) or periorbital cellulitis

The following is recommend regarding Eron Class II cellulitis:

Admission may not be necessary if the facilities and expertise are available in the community to give intravenous antibiotics and monitor the person

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21
Q

Management of cellulitis

A
  • flucloxacillin as first-line for mild/moderate cellulitis

*Clarithromycin, erythromycin (in pregnancy) or doxycyline is recommended in patients allergic to penicillin

severe cellulitis → co-amoxiclav, cefuroxime, clindamycin or ceftriaxone

22
Q

Is cellulitis bilateral or unilateral?

A

Almost always unilateral

23
Q

Spot diagnosis?

A

Erysipelas

  • streptococcal cellulitis
  • tends to be unilatera/on the face
  • pt may be systemically unwell
  • Management: antibiotics
24
Q

Spot diagnosis

A

Staphylococcal scalded skin syndrome

25
Q

What’s SSSS?

A

Staphylococcal scalded skin syndrome (SSSS)

  • serious skin infection
  • caused by the Staphylococcus aureus
  • toxins from staph (exfoliating)
  • usually in children

Management: IV antibiotics + fluids + analgesia

*doesn’t scar

* usually outcome is good if treated

26
Q

Conditions associated with sensitivity to streptococcal antigen

A
  • erythema nodosum
  • guttate psoriasis
  • vasculitis (Henoch-Schonlein Purpura)
  • glumerulonephritis
27
Q

Hx:

  • Pt brought in by ambulance
  • Low BP, temperature unwell
  • septic shock-like picture

What’s the diagnosis?

A

Necrotising fascitis

28
Q

Classification of nerotising fascitis

A

It can be classified according to the causative organism:

  • type 1 is caused by mixed anaerobes and aerobes (often occurs post-surgery in diabetics) This is the most common type
  • type 2 is caused by Streptococcus pyogenes
29
Q

Features of necrotising fascitis

A
  • acute onset
  • painful, erythematous lesion develops
  • often presents as rapidly worsening cellulitis with pain out of keeping with physical features
  • extremely tender over infected tissue
30
Q

Management of necrotising fascitis

A
  • urgent surgical referral debridement
  • intravenous antibiotics
31
Q

Spot diagnosis

A

Herpes simplex virus (cold sore)

Caused by: HSV-1

Management: topical aciclovir

32
Q

Spot diagnosis

A

Eczema Herpeticum

33
Q

What’s Eczema Herpeticum?

It’s management

A

Eczema herpeticum

  • severe primary infection of the skin by herpes simplex virus 1 or 2
  • more commonly seen in children with atopic eczema
  • often presents as a rapidly progressing painful rash

Management: As it is potentially life-threatening children should be admitted for IV aciclovir

*sometimes antibiotics are required if also infected with bacteria

34
Q

Describe lesion in eczema herpeticum

A
  • monomorphic punched-out erosions (circular, depressed, ulcerated lesions)
  • usually 1–3 mm in diameter
35
Q

Spot diagnosis

A

Varicella-Zoster - chicken pox

Chickenpox is caused by primary infection with varicella zoster virus

*Shingles is a reactivation of the dormant virus in dorsal root ganglion

36
Q

Spread and infectivity of chicken-pox

A
  • Chickenpox is highly infectious
  • spread via the respiratory route
  • can be caught from someone with shingles
  • infectivity = 4 days before rash, until 5 days after the rash first appeared
  • incubation period = 10-21 days
37
Q

Clinical features of chickenpox

A
  • tend to be more severe in older children/adults
  • fever initially
  • itchy, rash starting on head/trunk before spreading. Initially macular then papular then vesicular
  • systemic upset is usually mild
38
Q

Management of chickenpox

A

Management is supportive

  • keep cool, trim nails
  • calamine lotion
  • immunocompromised patients and newborns with peripartum exposure should receive varicella zoster immunoglobulin (VZIG). If chickenpox develops then IV aciclovir should be considered
39
Q

School excision in chickenpox

A

NICE:

  • Advise that the most infectious period is 1–2 days before the rash appears, but infectivity continues until all the lesions are dry and have crusted over (usually about 5 days after the onset of the rash).
40
Q

Potential complications of chicken pox

A

A common complication is secondary bacterial infection of the lesions

  • NSAIDs may increase this risk
  • whilst this commonly may manifest as a single infected lesion/small area of cellulitis, in a small number of patients invasive group A streptococcal soft tissue infections may occur resulting in necrotizing fasciitis

Rare complications include

  • pneumonia
  • encephalitis (cerebellar involvement may be seen)
  • disseminated haemorrhagic chickenpox
  • arthritis, nephritis and pancreatitis may very rarely be seen
41
Q

Spot diagnosis and management

A

Shingles

  • Shingles is an acute, unilateral, painful blistering rash caused by reactivation of the Varicella Zoster Virus (VZV)
  • Oral aciclovir is first-line.
  • One of the main benefits of treatment is a reduction in the incidence of post-herpetic neuralgia.
42
Q

Shingles vaccine

A

Vaccine to boost the immunity of elderly people against herpes zoster. Some important points about the vaccine:

  • offered to all patients aged 70-79 years
  • is live-attenuated and given sub-cutaneously

*As it is a live-attenuated vaccine the main contraindications are immunosuppression

Side-effects

  • injection site reactions
  • less than 1 in 10,000 individuals will develop chickenpox
43
Q

Foetal varicella-zoster syndrome

  • timeframe in pregnancy
  • features
A

Fetal varicella syndrome (FVS)

  • risk of FVS following maternal varicella exposure is around 1% if occurs before 20 weeks gestation
  • very small number of cases occurring between 20-28 weeks gestation and none following 28 weeks
  • features of FVS include skin scarring, eye defects (microphthalmia), limb hypoplasia, microcephaly and learning disabilities
44
Q

Other (apart from foetal varicella-zoster) risks to foetus

A

Other risks to the fetus

  • shingles in infancy: 1-2% risk if maternal exposure in the second or third trimester
  • severe neonatal varicella: if the mother develops rash between 5 days before and 2 days after birth there is a risk of neonatal varicella, which may be fatal to the newborn child in around 20% of cases
45
Q

Management of chickenpox exposure in pregnancy

A
  • if there is any doubt about the mother previously having chickenpox maternal blood should be urgently checked for varicella antibodies
  • if the pregnant woman is not immune to varicella she should be given varicella-zoster immunoglobulin (VZIG) as soon as possible. RCOG and Greenbook guidelines (effective up to 10 days post exposure)
  • oral aciclovir should be given if pregnant women with chickenpox present within 24 hours of onset of the rash
46
Q

What’s Herpes Zoster Opthalmicus? (what happens in it?)

A

Herpes zoster ophthalmicus (HZO)

  • reactivation of the varicella-zoster virus in the area supplied by the ophthalmic division of the trigeminal nerve
  • accounts for around 10% of case of shingles
47
Q

Features of Herpes Zoster Opthalmicus

A
  • vesicular rash around the eye, which may or may not involve the actual eye itself
  • Hutchinson’s sign: rash on the tip or side of the nose. Indicates nasociliary involvement and is a strong risk factor for ocular involvement → this is due to naso-cilliary n. involvement - call for ophthalmologist!!!
48
Q

Management of Herpes Zoster Opthalmicus

A
  • oral antiviral treatment for 7-10 days
    • ideally started within 72 hours
    • intravenous antivirals may be given for very severe infection or if the patient is immunocompromised
  • topical corticosteroids may be used to treat any secondary inflammation of the eye
  • ocular involvement requires urgent ophthalmology review
49
Q

Possible complications of Herpes Zoster Opthalmicus

A
  • ocular: conjunctivitis, keratitis, episcleritis, anterior uveitis
  • ptosis
  • post-herpetic neuralgia
50
Q

Spot diagnosis

A

Warts

(caused by Human Papilloma Virus)

Y4 Lecture Day III (9 decks)

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