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Y2 MCD Microbiology > skin infections > Flashcards

skin infections Flashcards

skin infections: summarise the epidemiology of organisms that commonly cause skin infections, and recall the biology and main clinical features of common skin infections and infestations, including Staphylococcus aureus, Treponema pallidum, herpes simplex, varicella zoster, Trichophytum rubrum and Sarcoptes scabei

1
Q

epidemiology of skin disease

A

skin disease common, with skin high infection rates in hot humid conditions and poor populations

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2
Q

skin disease due to infection in GP vs hospital

A

more infection % in GP than hospitals

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3
Q

prevalence of skin infection by geographical infection

A

malignant tumours higher in white areas; bacterial, fungal, eczema/dermatitis higher in developing countries

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4
Q

describe appearance of Staph. aureus

A

“bundles of grapes” with a capsule

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5
Q

commensal Staph. aureus location (but can become skin infection)

A

nose, armpits and groin

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6
Q

resistant Staph. aureus

A

MRSA (not worse just harder to treat)

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7
Q

4 toxins produced by Staph. aureus and what they cause

A

panton valentine leucocidin (aggressive soft tissue infection), exfoliative toxin (blisters), TSST-1 (septicaemic features), enterotoxin (causes diarrhoea from contamination of food)

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8
Q

besides skin infection, what else can it infect (can go on and cause sepsis)

A

bone, joint and lung (lung particularly after flu)

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9
Q

infection of Staph. aureus in subcorneal layer of epidermis

A

impetigo (honey-coloured crustic erosion; can produce exfoliative toxin causing splitting of skin to form bullous - blisters containing bacteria which cause puss)

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10
Q

infection of Staph. aureus of mouth of hair follicle

A

folliculitits

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11
Q

infection of Staph. aureus of full thickness of epidermis

A

ecythma (crusted thick lesion with necrotic surface of skin, forming thick scar; caused by infected insect bite)

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12
Q

infection of Staph. aureus causing abscess of puss of hair follicle

A

boil (same as abscess)

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13
Q

infection of Staph. aureus causing multiple abscesses of several adjacent hair follicle

A

carbuncle

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14
Q

who is affected by staphylococccal scalded skin syndrome

A

children under 5 (Staph. aureus causing superficial cleavage of skin)

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15
Q

how is staphylococccal scalded skin syndrome treated

A

antibiotics

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16
Q

key features of Staph. auereus

A

variety of presentations, golden crust, diagnosed by swab, determine which antibiotics it will respond to

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17
Q

what is Treponema pallidum

A

spiral gram -ve bacteria causing syphilis (STD)

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18
Q

3 phases of syphilis

A

primary, secondary, latent syphilis, tertiary syphilis

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19
Q

describe primary stage of syphilis

A

3-8 weeks after inoculation, causing painless ulcer (weepy ulcer on genitals or mouth)

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20
Q

describe secondary stage of syphilis

A

6-12 weeks after inoculation, disseminated infection, generalised rash and lymphadenopathy. with ondyloma lata “warty” regions present too

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21
Q

describe tertiary stage of syphilis

A

years later, causing inflammatory lesions affecting skin, neurological and vascular (can also cause thoracic aneurysms)

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22
Q

describe congenital syphilis

A

acquired perinatally with early and late manifestations

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23
Q

what can neurosyphilis cause

A

dementia

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24
Q

pregnancy risks of congenital syphilis

A

miscarriage, still birth, prematurity, rashes, brain and neurological problems, bone disease

25
Q

diagnosis of primary syphilis

A

swab, blood test (may or may not be positive)

26
Q

diagnosis of secondary and later syphilis

A

serology positive; can be made by rash and biopsy (plasma cells present)

27
Q

treatment of syphilis

A

antibiotics

28
Q

3 members of human herpes virus family ( with latency site of neurones (can reactivate)

A

HSV-1 (affects around mouth), HSV-2 (affects around genitals), VZV (causes chickenpox and shingles)

29
Q

presentation of herpes simplex (HSV-1 and 2)

A

vesicular rash (present on mouth, genitals or anywhere else but heal after 2 weeks; with HSV-2 can form crusty blisters); at stress/illness can reactivate

30
Q

eczema risk and what herpes infection causes in patients with eczema

A

defective barrier function so susceptible to skin infection (with herpes, causes eczema herpeticum)

31
Q

diagnosis of herpes simplex

A

clinical, swab for PCR

32
Q

treatment of herpes simplex

A

acyclovir

33
Q

VZV (herpes varicella zoster, chickenpox or shingles) virus incubation

A

incubation after 1 week: malaise, fever, sore throat, lethargic -> rash with groups of vesicles on erythematous base, concentrated centripetally (face and trunk)

34
Q

complications of VZV

A

encephalitis (inflammation of brain), pneumonia in elderly

35
Q

describe reactivation of latent VZV

A

latent in dorsal root ganglion but reactivates in stress/illness (only down one dermatome)

36
Q

symptoms of VZV if effects V1 nerve

A

facial VZV, causing pain and potentially causing blindness

37
Q

vaccine for chickenpox and shingles

A

no vaccine for children with chickenpox, vaccine for elderly with shingles

38
Q

2 types of superficial skin fungal infections

A

dermatophytes (mould), yeasts

39
Q

where are dermatophytes present

A

grows in keratin so affects skin, hair and nails

40
Q

where are yeast (e.g. candida) present

A

grow on warm, wet surfaces in body folds

41
Q

what happens to nails in Tinea unguium (dermatophyte)

A

become yellow and crumbly

42
Q

who are affected by Tinea capitis (dermatophyte)

A

affect prepubertal children

43
Q

presentation of Tinea capitis (dermatophyte)

A

crusty lesion on scalp or kerion (boggy mass with pustules) - affects Afrocaribbean children more

44
Q

location of Tinea manuum

A

affects hands

45
Q

location of Tinea pedis

A

affects toes

46
Q

location of Tinea cruris

A

affects skin of inner thigh

47
Q

location of Tinea facei

A

affects face

48
Q

how can Tinea dermatophytes be transmitted

A

via pets

49
Q

candida presentation

A

red, sore, spotty

50
Q

diagnosis of superficial skin fungal infections

A

scrapings of rash, clippings of nail or pluckings of hair -> cultured/PCR

51
Q

treatment of dermatophytes

A

terbinafine (cream if skin, tablets if not)

52
Q

treatment of candida

A

antifungal cream

53
Q

what causes scabies

A

mites (female burrows into stratum cornea and lays eggs)

54
Q

diagnosis of scabies

A

look for burrow (4mm long squiggle with black dot (head of mite) at one end)

55
Q

common sites of scabies burrows

A

finger webs, toe webs, genital area (inflammatory lumps), axilla

56
Q

describe reaction to scabies mites

A

initial infection is asymptomatic, but after 4 weeks develop immune reaction to cause widespread eczema

57
Q

treatment for scabies

A

insecticide cream

58
Q

transmission of scabies

A

direct contact for many minutes

59
Q

consequences of secondary bacterial infections following chronic scabies

A

cause renal failure due to skin infections of Streptococcus

Y2 MCD Microbiology (9 decks)

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