Skin infections Flashcards
Where is Staphylococcus aureus often found?
As a skin commensal In skin infections
What are the the toxins sometimes produced by Staphylococcus aureus?
- Panton Valentine Leuocidin (PVL)
- Exfoliative toxin
- TSST-1 (Toxic Shock Syndrome Toxin 1)
- Enterotoxin
What happens in Staphylococcus aureus infections producing PVL?
Necrotising damage Much more serious infection
What is exfoliative toxin?
- Produced in some Staphylococcus aureus infections
- Targets the same antigens as in pempigus vulgaris (desmoglein 1 & 3)
What kind of infections does staphylococcus aureus cause?
Skin Bone Joint Lung
What are the different skin infections of staphylococcus aureus?
- 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
What is very characteristic of Staphylococcus aureus skin infection?
Gold coloured crust
What does exfoliative toxin producing Staphylococcus aureus infections cause in adults?
Bullous impetigo
Cleavage of the skin in the epidermis above the BM
When does ecthyma often develop?
After insect bites
How is an abscess treated?
Incision and drainage of the abscess to let the puss out
What does exfoliative toxin producing Staphylococcus aureus infections cause in children?
- Staphylococcal scalded skin syndrome
- Only affects children under 5
- Widespread erythema and exfoliation (to come off in scales/flakes)
What is the treatment for Staphylococcus aureus infection?
- Flucloxacillin
- If MRSA - erythromycin or clarithromycin
What causes syphillis?
Treponema pallidum
A gram neagtive spirochaete
What increases your chance of getting syphilis?
It’s an STD so sexual contact
Having other STDs esp HIV
What are the stages of acquired Syphilis?
- Primary (3-8 weeks)
- Painless ulcer (chancre) at inoculation site
- Heals up and disappears quickly
- 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)
- Latent
- Tertiary syphilis (years later)
* Skin, neurological, bone and vascular (aortic aneurysms) manifestations
What does congenital syphilis cause?
- Early and late miscarriages
- Still births
- Pre-maturity
- Rashes
- Brain and neurological problems
- Bone disease
How is syphillis treated?
Screened before birth
Penicillin treatment very effective
What are the diseases caused by human herpes viruses 1-3 (HVVs)?
- HVV1 -> HSV 1 -> Oro-genital herpes
- HVV2 -> HSV 2 -> Oro-gential herpes
- HVV3 -> varicella zoster (VZV) -> Chickenpox and shingles
What can re-activate latent HSV?
- Stress
- Poor sleep
- Other illnesses
- Sun exposure
What are the target cells and latency site for HVV 1-3?
- Target cell - Muco-epithelial cells
- Latency cells - neurones (dorsal root ganglion)
What are the clinical presentations of HSV?
- 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
Generally, what type of herpes do HSV1 and HSV2 cause?
- HSV1 - oral herpes
- HSV2 - genital herpes
Note:
Not always the case, they can both cause both types, above is just the most common
Is the inital or subsequent HSV infections worse?
Initial can be much worse
Where is chicken pox focused?
- Primarily on the face
- Then body
- Least on arms and legs
What is the outcome of a chicken pox infection?
- Usually resolves itself
- Rarely can cause:
- pneumonia
- encephalitis
- death
What is the other name for shingles?
Herpes zoster
What can cause reactivation of varicella zoster?
Low immunity
Explain the presentation of herpes zoster?
- 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
What does herpes zoster of the nasociliary nerve cause?
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
What are the 2 types of superficial skin fungal infections?
- Dermatophytes
- e.g. Trichophyton rubrum
- Cause ‘tinea’ infections
- Grow in keatin
- Yeasts
- E.g. candida
- Grow on warm wet surfaces
What are the features of tinea unguium?
Usually a dermatophytes infection
Yellow crumbly destruction of the nail
How are nail fungal infections treated?
Systemic antifungals - the infection is too deep in the nail for topicals
Who gets tinea capitis?
Only children pre-puberty
Usually afro Carribean origin - structure of their hair
What is kerion?
Dermatophyte infection
Produces well defined abscess like lesions
Why must fungal infections involving the hair be treated with systemic ant fungals?
The infection will have penetrated the hair follicle canal and be too deep for topicals
What is candida intertrigo?
- 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
What causes scabies?
Sarcoptes scabei
Where do scabies burrow?
Underneath the stratum corneum
What happens 4 weeks after an inital scabies infection?
Allergic reaction to scabies eggs and faeces
Widespread eczema
What is the treatment for scabies?
Insecticide cream from the neck down for 12 hours, repeat 5 days after
What are the common sites of scabies infection?
