Skin infections

Question 1

what % of GP appointments are skin related

Answer 1

15%

Question 2

where are skin infections more common

Answer 2

Skin conditions are more common in hot, humid climates amongst poorer populations (opposite in dry/rich)

Question 3

what are the features of a Staph. A skin infection

Answer 3

A gram+ bacteria, commensal in approx. 30% of humans with colonisation in the nose, axilla and groin.

SA is the most common bacterial cause of skin infections including:
-impetigo (and bullous (blistering) impetigo), (infection of
sub-corneal layer of epidermis)- especially around
mouth and nose
-folliculitis (infection of mouth of hair follicle)
-ecthyma (infection of full thickness of epidermis)
-boils (abscess of hair follicle)
-carbuncles (abscess of several adjacent hair follicles)

Question 4

what diseases does staph A cause

Answer 4

Staphylococcal Scalded Skin Syndrome– Exfoliative toxin.

Toxic shock Syndrome – Toxic Shock Syndrome Toxin-1 (TSST-1).

Food poisoning–Enterotoxin.

Necrotising soft tissue infections– Panton Valentine Leucocidin virulence facto

Question 5

what bacteria causes syphilis

Answer 5

Treponema pallidum, gram -ve

Question 6

describe the 3 stages of syphilis (Treponema pallidum)

Answer 6

primary: painless ulcers (chancre) at site of inoculation (genitals/oral as its an STI)
secondary: spread rash (maculopapular-small flat red dots on skin), lymphadenopathy

latent: after an asymptomatic period– skin
(gummatous skin lesions, bone lesions), neurological (depression/ dementia)and vascular manifestations (thoracic aneurysm)

NOTE: can be vertically transmitted and cause congenital syphilis: Babies born alive have features similar to secondary syphilis: rashes

Question 7

what are the 3 main types of herpes virus and what do they cause (yes there are more but the ones we need to know for micro)

Answer 7

HSV-1: Oral herpes (HHV-1)
HSV-2: Genital herpes (HHV-2)

Varicella Zoster (HHV-3)
o primary infection:
    -chicken pox
o latent infections:
    -shingles

All spread by skin-skin contact

Question 8

what type of infection is Trichophyton rubrum

Answer 8

Fungal- Dermatophytes (mould)

Question 9

where can Trichophyton rubrum grow and live

Answer 9

grow and live in keratin (skin, hair, nails)

Question 10

what are the different names for infections of the skin, hair and nails by Trichophyton rubrum

Answer 10

prefixed with the Latin “tinea” followed by the body part:

• tinea unguium (nails)
• tinea capitis (kerion) (scalp)
• tinea manum (hands)
• tinea pedis (feet)

Question 11

what are the clinical features of HSV1 and HSV2 and what are the treatments

Answer 11

Clinical features involve:
-painful vesicular rash (heals over 2-4 weeks), eczema herpeticum, herpes encephalitis. Can have reinfections due to latency in sensory neurones

treatment=antivirals eg acyclovir

Question 12

what are the clinical features of VZV

Answer 12

o primary infection:
-chicken pox: erythematous asynchronous rash (face,
trunk, arms, legs)
o latent infections:
-shingles: reactivation of the VZV and a painful
vesicular rash appears along the course of a
dermatome (usually heals in 2-4 weeks)
( post-herpetic neuralgia^)

Question 13

whats another type of fungal infection (that’s not Dermatophytes) and give an example

Answer 13

yeasts- eg: Candida (grow in warm/wet places)

Question 14

what are the clinical presentations of candida infections

and what is the treatment

Answer 14

eryhthromatous scaly rash on skin/scalp, discoloured or crumbly nails

treated with: topical or systemic anti-fungal medications

Question 15

what causes scabies and how is it spread

Answer 15

Sarcoptes scabei - skin to skin transmission

Question 16

how is syphilis treated?

Answer 16

Syphilis responds well to penicillin antibiotics

Question 17

where is Candida intertrigo usually found

Answer 17

body folds- axilla, under breasts, genital area etc…

Question 18

how would you treat a patient with scabies

Answer 18

Treated with an insecticide cream, put on all over the body:

• The cream must be left on the body for 12 hours
• This is repeated 5 to 7 days later – this should clear it
• All the household contacts should be treated at the same time
• All their clothes and bedding are often washed at over 55 degrees – but this isn’t so essential as mites can’t survive long off the body

Question 19

where are the common burry sites for scabies mites

Answer 19

fingers, buttocks, genitals, wrists, axilla, instep of feet

The female mites make the burrows, and the male mites walk on the skin (but they are never seen)

Question 20

how do scabies cause a rash

Answer 20

after burying under the skin- exposure to the mite faeces and eggs cause a delayed-type allergic reaction resulting in widespread eczematous rash occurring ~4 weeks after first infestation.

Question 21

what is crusted scabies

Answer 21

normal scabies infections involve 15-20 mites,

in immunocompromised patients this could involve THOUSANDS of mites- crusted scabies