Skin Infections Flashcards by patrick ellis

What is the name of this disease? [1]

Which pathogen is the most likely cause of this infection? [1]

Impetigo;
Staph. aureus most common

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Which pathogen causes this symptom? [1]

Candida albicans

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[] are a unique population of tissue-resident macrophages that form a network of cells across the epidermis of the skin, but which have the ability to migrate from the epidermis to draining lymph nodes (LN)

Langerhan cells

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What pathogen causes this symptom? [1]

HSV-1

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Describe how your skin is a hostile environment [3]

Physical barrier
* Dry
* Desquamates (constant shedding)

Chemical barrier
* Eccrine, apocrine and sebaceous glands: feed good bacteria
* Unsaturated fatty acids (oleic acid)

Bacterial interference
* Colonisation by non pathogenic skin flora (microbiome of the skin): outcompete bad bacteria

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Normal skin biome is made up from which:

bacteria [3]
yeasts [3]
viruses [3]

bacteria:
* Staphylococcus
* proprionobacteria
* corynebacteria

yeasts
* malassezia,
* aspergillus
* Cryptococcus

viruses:
* HPV
* EBV
* HHV8

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Role of normal skin flora? [2]

Produces molecules that inhibit colonisation of other species

Educates the innate and adaptive immune response (Inflammation)

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Where are the 3 main microenvironments of the skin? [3]

Axilla, perineum and toe webs (moist)
Hands, face and trunk (oily)
Upper arms and legs (dry)

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Which is the major inhabitant making up more than 90% of the flora? [1]

Staphylococcus epidermidis

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Which species of your normal skin flora:

Makes up 90% of the flora? [1]

Is found in nose, perineum, vulvar skin? [1]

Feeds off sebum and cellular debris and colonisation starts when sebaceous glands become more active?

Makes up 90% of the flora: Staphylococcus epidermidis

Is found in nose, perineum, vulvar skin: Staphylococcus aureus

Feeds off sebum and cellular debris and colonisation starts when sebaceous glands become more active: Propionibacterium acnes

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Which bacteriia is found more in the nose, perineum & vulvar skin? [1]

(occurrence in nasal passages varies with age)

Staphylococcus aureus

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Main pathogen that causes folliculitis? [1]

Staphylococcus aureus

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Describe the relationship of Staphylococcus epidermidis
and Staphylococcus aureus in a period of atopic dermatitis? [1]

S. epidermidis increases as an antagonistic response to an increase in S. aureus population in atopic dermatitis

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How does folliculitis occur? [1]

Infection and inflammation of one or more hair follicles

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Which pathogen causes hot tub folliculitis? [1]

Pseudomonas aeruginosa

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Treatment for folliculitis? [3]

Oral antibiotic
Retinoic acid & Vit. A: reduces amount of sebum

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Two primary pathogens that cause impetigo? [2]

Staphylococcus aureus or Streptococcus pyogenes

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Tx of impetigo?:

Simple cases [1]
Severe cases? [1]
Most people? [1]

Oral or topical antibiotic for severe cases that have spread to other body areas

NICE recommends 1% hydrogen peroxide cream for simple cases

But most people will get better without treatment within 3 weeks

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Describe the pathogenensis of cellulitis [2]

Infection of the dermis and subcutaneous fat caused by Staphylococcus aureus or Streptococcus pyogenes due to break in skin

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What is cellulitis in the face called? [1]

How does it differ to cellulitis in location? [1]

Most common pathogen? [1]

Erysipelas (cellulitis of the face) but just in the dermis and not in subcutaneous fat

Streptococcus pyogenes

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What is this skin infection? [1]

Which pathogen causes this? [1]

Scalded skin syndrome:
Staphylococcus aureus

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Describe the pathophysiology of scalded skin syndrome [2]

Exotoxins are proteases that destroy desmosomes holding keratinocytes in granulosum and spinosum layers together:

Causes widespread fluid filled blisters that easily break

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Treatment of scalded skin syndrome? [2]

Treatment:
* Conservative: rehydration antipyretics
* Parenteral antibiotics

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What is Nikolsky sign and what does it test? [1]

Nikolsky sign is a test of how weak the blister is.

Pencil eraser placed on top of blister and turned if blister ruptures the blister is intraepidermal. Or you turn the eraser on unblistered skin and new blister forms.

Name this disease [1]

**Necrotising fasciitis**

Therapy for Necrotising fascitis? [3]

Treatment: * **Surgical debridement** * Empiric **antibiotics** * **Hyperbaric oxygen** (Add on therapy)

Warts and verrucas arise from an infection of which layer of the skin? stratum basale. stratum spinosum. stratum granulosum. stratum lucidum. stratum corneum.

**stratum basale**

Which layer of the epidermis is only found in places with thickened skin like the hands and feet? stratum basale. stratum spinosum. stratum granulosum. stratum lucidum. stratum corneum.

stratum lucidum.

What pathogen causes this symptom? [1]

Human papillomavirus: causes **viral warts and verruca (plantar warts)**

Describe pathophysiology of HPV causing warts and verrucas [3]

DNA virus **Infects basal cells of the epidermis** Lesions arise from **proliferation of infected basal keratinocytes** Causes **hyperkeratosis, acanthosis and hypergranulosis, rete ridge elongation** and **large blood vessels** at **dermoepidermal junction**

Treatment for HPV: viral warts and veruccas? [5]

Topical salicylic acid Fluorouracil cream Cryosurgery Surgical curettage Laser treatment (CO2 laser 582nm)

Name this symptom of Herpes virus [1]

Herpatic whitlow

Shingles is caused by reactivation of which virus? varicella zoster virus epstein barr virus herpes virus human papilloma virus

**varicella zoster virus**

Describe what the symptoms of a shingles rash is like [1]

**Typically single wide stripe** either on the left or right side of the body

Describe what Postherpetic neuralgia (PHN) is [2]

Unpredictable complication of **varicella zoster virus- (VZV-)** induced **herpes zoster (HZ)** which often occurs in elderly and immunocompromised persons The main symptom of post-herpetic neuralgia is **intermittent or continuous nerve pain** in an area of your skin previously affected by shingles.

What causes this symptom? [1] Where are patients commonl affected? [1] How do patients commonly present? [1]

**Molluscum contagiosum**: water warts Moist areas more common such as **abdomen, groin, axilla** **Pink, smooth with dimple in the middle** (full of dead cells)

Treatment of Molluscum contagiosum? [1]

Usually resolves without treatment If severe or in genital area then OTC wart treatments, cryo-surgery

What causes this symptom? [1]

**Candida albicans**: Opportunistic infection genital thrush, intertrigo, oral plaques, paronychia (nail fold)

What predisposes patients to candida albicans overgrowth? [5]

moist environment, obesity, diabetes, antibiotics, immunosuppression

What causes this symptom? [1]

**Pityriasis versicolour** (tinea versicolour)

Describe the pathophysiology of **Pityriasis versicolour** [1] Which populations does it impact more? [1]

**Overgrowth of commensal yeast Pityrosporum orbiculare**; young adults, brown/pink scaly patches, **hypopigmented if suntanned** Affects **young adults and slightly more men than women**: It is **not contagious infection is not due to poor hygiene usually occurs in warmer months white, salmon or light brown patches chest,back, arms and legs** More common in hot humid climates and only affects people that sweat heavily Often clears during the winter months and reappears each summer

Treatment of Pityriasis versicolour (tinea versicolour)? [3]

* **Antifungal shampoo** (ketoconazole) * **Selenium sulphide** (off-label) * For **small areas antifungal creams**

What are dermatophytes? [1]

Dermatophytes are fungal organisms that require **keratin** for growth.

Describe pathophysiology of scabies [2]

**Sarcoptes scabiei (hominis)** female mite infestation: 10-15 mites Symptoms are an **allergic reaction to mites that burrow and lay eggs in skin**

Treatment of scabies? [3]

Treatment: * **permethrin** * ivermectin * crotamiton

Lyme disease is caused by ticks spreading which bacteria? [1] Describe symptoms [2]

**Borrelia bacteria** * Expanding red rash 70-80% of patients * Rash is oval not itchy or painful and resolves (untreated) in around 4 weeks accompanied with flu like systemic illness

Treatment of Lymes disease? [2]

Removal of the tick (if still there) Antibiotics 1-4 weeks

What causes this symptom? [1]

**Lupus vulgaris**: TB of the skin

Where does lupus vulgaris commonly occur? [2]

Painful cutaneous tuberculosis skin lesion most often on the **face around nose, eyelids, lips and cheeks**. May develop into **disfiguring skin ulcers if left untreated**

What is Scrofuloderma (scrofula)?

**lymphatic dissemination of pulmonary TB**

Leprosy is caused by which pathogens? [2]

**Mycobacterium leprae** or **mycobacterium lepromatosis**

Treatment for leprosy? [3]

Rifampicin, dapsone and clofazimine

Which of the following are you most likely to find in your nose, perineum and vulvar skin? Staphylococcus aureus Staphylococcus epidermidis Propionibacterium acnes Malassezia pachydermatis

Which of the following are you most likely to find in your nose, perineum and vulvar skin? **Staphylococcus aureus** Staphylococcus epidermidis Propionibacterium acnes Malassezia pachydermatis

Which of the following feeds off sebum and cellular debris? Staphylococcus aureus Staphylococcus epidermidis Propionibacterium acnes Malassezia pachydermatis

Which of the following feeds off sebum and cellular debris? Staphylococcus aureus Staphylococcus epidermidis **Propionibacterium acnes** Malassezia pachydermatis

Describe the relationship of Staphylococcus epidermidis and Staphylococcus aureus in a period of atopic dermatitis? [1]

**S. epidermidis** **increases** as an **antagonistic response** to an **increase** in **S. aureus** population in atopic dermatitis

Which of the following causes hot tub folliculitis? Human Papilloma Virus Streptococcus pyogenes Pseudomonas aeruginosa Staphylococcus aureus

**Pseudomonas aeruginosa**

Which of the following causes hot tub folliculitis? Human Papilloma Virus Streptococcus pyogenes Pseudomonas aeruginosa Staphylococcus aureus

**Pseudomonas aeruginosa**