Skin infections Flashcards

1
Q

Where is Staphylococcus aureus often found?

A

As a skin commensal In skin infections

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2
Q

What are the the toxins sometimes produced by Staphylococcus aureus?

A
  • Panton Valentine Leuocidin (PVL)
  • Exfoliative toxin
  • TSST-1 (Toxic Shock Syndrome Toxin 1)
  • Enterotoxin
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3
Q

What happens in Staphylococcus aureus infections producing PVL?

A

Necrotising damage Much more serious infection

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4
Q

What is exfoliative toxin?

A
  • Produced in some Staphylococcus aureus infections
  • Targets the same antigens as in pempigus vulgaris (desmoglein 1 & 3)
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5
Q

What kind of infections does staphylococcus aureus cause?

A

Skin Bone Joint Lung

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6
Q

What are the different skin infections of staphylococcus aureus?

A
  • Impetigo - subcorneal layer of epidermis
  • Folliculitis - mouth of the hair follicle
  • Ecthyma - full thickness of the epidermis and possibly the superficial dermis
  • Boil - abscess (pus filled inflammed area) of hair follicle
  • Carbuncle - Abscess of several adjacent hair follicles
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7
Q

What is very characteristic of Staphylococcus aureus skin infection?

A

Gold coloured crust

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8
Q

What does exfoliative toxin producing Staphylococcus aureus infections cause in adults?

A

Bullous impetigo

Cleavage of the skin in the epidermis above the BM

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9
Q

When does ecthyma often develop?

A

After insect bites

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10
Q

How is an abscess treated?

A

Incision and drainage of the abscess to let the puss out

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11
Q

What does exfoliative toxin producing Staphylococcus aureus infections cause in children?

A
  • Staphylococcal scalded skin syndrome
  • Only affects children under 5
  • Widespread erythema and exfoliation (to come off in scales/flakes)
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12
Q

What is the treatment for Staphylococcus aureus infection?

A
  • Flucloxacillin
  • If MRSA - erythromycin or clarithromycin
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13
Q

What causes syphillis?

A

Treponema pallidum

A gram neagtive spirochaete

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14
Q

What increases your chance of getting syphilis?

A

It’s an STD so sexual contact

Having other STDs esp HIV

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15
Q

What are the stages of acquired Syphilis?

A
  1. Primary (3-8 weeks)
  • Painless ulcer (chancre) at inoculation site
  • Heals up and disappears quickly
  1. Secondary (6-12 weeks)
  • Disseminated to lymph nodes - lymphadenopathy
  • Generalised rash all over the body including palms and soles
  • Septicemia like symptoms
  • Axillary and groin warty lesions (condyloma lata - not actual warts)
  1. Latent
  2. Tertiary syphilis (years later)
    * Skin, neurological, bone and vascular (aortic aneurysms) manifestations
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16
Q

What does congenital syphilis cause?

A
  • Early and late miscarriages
  • Still births
  • Pre-maturity
  • Rashes
  • Brain and neurological problems
  • Bone disease
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17
Q

How is syphillis treated?

A

Screened before birth

Penicillin treatment very effective

18
Q

What are the diseases caused by human herpes viruses 1-3 (HVVs)?

A
  • HVV1 -> HSV 1 -> Oro-genital herpes
  • HVV2 -> HSV 2 -> Oro-gential herpes
  • HVV3 -> varicella zoster (VZV) -> Chickenpox and shingles
19
Q

What can re-activate latent HSV?

A
  • Stress
  • Poor sleep
  • Other illnesses
  • Sun exposure
20
Q

What are the target cells and latency site for HVV 1-3?

A
  • Target cell - Muco-epithelial cells
  • Latency cells - neurones (dorsal root ganglion)
21
Q

What are the clinical presentations of HSV?

A
  • Vesicular rash - 2 weeks
  • Pain before the appearance of the rash
  • Eczema herpeticum
  • Herpes encephalitis - inflammation of the brain causing focal neurology and reduced consciousness
  • Stomatitis - inflammation of mouth and lips
22
Q

Generally, what type of herpes do HSV1 and HSV2 cause?

A
  • HSV1 - oral herpes
  • HSV2 - genital herpes

Note:

Not always the case, they can both cause both types, above is just the most common

23
Q

Is the inital or subsequent HSV infections worse?

A

Initial can be much worse

24
Q

Where is chicken pox focused?

A
  • Primarily on the face
  • Then body
  • Least on arms and legs
25
Q

What is the outcome of a chicken pox infection?

A
  1. Usually resolves itself
  2. Rarely can cause:
  • pneumonia
  • encephalitis
  • death
26
Q

What is the other name for shingles?

A

Herpes zoster

27
Q

What can cause reactivation of varicella zoster?

A

Low immunity

28
Q

Explain the presentation of herpes zoster?

A
  • Varicella zoster is latent in dorsal root ganglion
  • When reactivated it effects the dermatome of the nerve is was latent in
  • Inflammatory lesions along one dermatome
  • Doesn’t cross the midline
  • Can spread to other dermatomes
  • Can blister
29
Q

What does herpes zoster of the nasociliary nerve cause?

A

Nasociliary is one of the 3 branches of V1

Supplies the back of the eye and tip of the nose

Inflammation of back of the eye can lead to blindness

30
Q

What are the 2 types of superficial skin fungal infections?

A
  1. Dermatophytes
  • e.g. Trichophyton rubrum
  • Cause ‘tinea’ infections
  • Grow in keatin
  1. Yeasts
  • E.g. candida
  • Grow on warm wet surfaces
31
Q

What are the features of tinea unguium?

A

Usually a dermatophytes infection

Yellow crumbly destruction of the nail

32
Q

How are nail fungal infections treated?

A

Systemic antifungals - the infection is too deep in the nail for topicals

33
Q

Who gets tinea capitis?

A

Only children pre-puberty

Usually afro Carribean origin - structure of their hair

34
Q

What is kerion?

A

Dermatophyte infection

Produces well defined abscess like lesions

35
Q

Why must fungal infections involving the hair be treated with systemic ant fungals?

A

The infection will have penetrated the hair follicle canal and be too deep for topicals

36
Q

What is candida intertrigo?

A
  • Inflammation of a body crease usually where there is eczema overgrowth of candida yeast
  • There are satellite areas of rash away from the main rash
37
Q

What causes scabies?

A

Sarcoptes scabei

38
Q

Where do scabies burrow?

A

Underneath the stratum corneum

39
Q

What happens 4 weeks after an inital scabies infection?

A

Allergic reaction to scabies eggs and faeces

Widespread eczema

40
Q

What is the treatment for scabies?

A

Insecticide cream from the neck down for 12 hours, repeat 5 days after

41
Q

What are the common sites of scabies infection?

A