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Charis & Ellie vs Dermatology > Infectious Diseases > Flashcards

Infectious Diseases Flashcards

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Dermatology Board Prep flashcards
1
Q

what patients need single room isolation and contact precautions?

A

Patient with group A strep infection

Patients with MRSA infection

Patients with scabies (also need long sleeved gowns)

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2
Q

Bacterial skin infections

A

necrotising fasciitis staph aureus strep pyogenes

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3
Q

what is necrotising fasciitis?

A

bacterial infection which spreads along the fascial planes below the surface of the skin causing rapid tissue destruction very painful

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4
Q

What are the 2 types of necrotising fasciitis?

A

Type 1: mixed bacteria, usually post-abdominal surgery Type 2: group A strep infection

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5
Q

what is a common example of necrotising fasciitis getting into the skin?

A

infected leg ulcers - treat the anaeorbes especially if diabetic

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6
Q

What is a virulence factor?

A

protein components which impact the pathology process of an infection - they can vary between species of bacteria they change quickly - similar to antibiotic resistance

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7
Q

examples of virulence factors

A
  • Adhesin: enables binding of the organism to host tissue, collagen-binding proteins and fibrinogen-binding proteins are types of adhesins
  • Impedin: enables the organism to avoid host defence mechanisms
  • Aggressin: causes direct damage to the host
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8
Q

staph aureus

A

a gram +ve, coagulase +ve superficial infections are self-limiting systemic infections are life-threatening

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9
Q

what does staph aureus do in terms of skin infection?

A

Toxinoses: toxic shock, scalded skin syndrome Toxinoses [TSS-1] is a superantigen which is especially associated with toxic shock (e.g. from menstrual tampons), there is a massive release of cytokines and an inappropriate immune response Panton-valentine leukocidin [PVL] is a cytotoxin released by some strains of staph aureus which is associated with severe skin infections, can cause necrotising pneumonia

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10
Q

Strep pyogenes

A

Gram +ve
Beta-haemolysis
Lance field surface antigen and superantigens

GAS - group A streptococci

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11
Q

what skin infections are caused by strep pyogenes?

A

Impetigo [honey coloured crust, can also be caused by staph aureus, can be treated with flucloxacillin/fusidic acid]
Cellulitis [erysipelas]
Necrotising fasciitis

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12
Q

pathogenesis of strep pyogenes

A

streptolysin S - destroys immune cells virulence factors of strep pyogenes - damage the immune system Virulence varies through horizontal gene transfer e.g. throat infection [bacterial], Scarlett fever [Scarlett fever has symptoms like strawberry tongue, treated with penicillin]

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13
Q

why do anti-inflammatory drugs sometimes work?

A

some pathogens can use the immune response to get nutrients

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14
Q

causes of fungal skin infections?

A

ring worm candida

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15
Q

what is ring worm?

A

dermarophyte fungal infection

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16
Q

where in the body do you get ring worm?

A

Tinea: capitis (scalp, usually in children), barbae (beard), corporis (body), manuum (hand), unguium (nails), cruris (groin), pedis (foot - ‘athlete’s foot’, very common in those who have cellulitis)

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17
Q

who gets ring worm?

A

males more common - especially tinea cruris and tinea pedis

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18
Q

Where do you catch ring worm?

A

other infected humans (anthropophilic fungi), animals (zoophilic) and soil (geophilic fungi, this is less common in the UK)

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19
Q

Pathogenesis of ring worm?

A

fungus enters abraded/saggy skin, hyphae (part of the fungus) spreads in the keratin layer - it only infects keratinised tissues (hair, skin, laters), this causes increased epidermal turnover leading to scaling which provokes the inflammatory response in the dermis

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20
Q

how does ring worm present?

A

a ring appearance due to the lesion growing outward with healing in the centre

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21
Q

How is ring worm diagnosed?

A

clinical appearance woods light appearance skin scrapings - from the scaly edge of the lesion nail clippings, hair - send these in a dermapak

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22
Q

How is ring worm treated?

A

small areas of infected skin/ nails = clotrimazole (canestan) cream or topical nail paint (amorolfine) extensive skin/ nail infections, scalp infections = oral terbinafine, oral itraconazole

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23
Q

what is candida?

A

a fungal infection

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24
Q

what is candida intertrigo

A

infection in skin folds - under breasts, groin, abdominal skin folds, nappy rash in babies) patients commonly obese

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25
Q

why does candida intertigo infect skin folds?

A

because those areas are warm and moist

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26
Q

how is candida intertigo diagnosed?

A

swab for culture

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27
Q

how is candida intertigo treated?

A

clotrimazole cream oral fluconazole

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28
Q

What skin infections are caused by parasites?

A

scabies lice

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29
Q

What are scabies?

A

Caused by sarcoptes scabiei [Chronic crusted form = Norwegian scabies] Has an incubation period of up to 6 months

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30
Q

how does scabies present?

A

very itchy rash can cause burrows affect finger webs wrists genital area

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31
Q

how is scabies treated?

A

Permethrin cream (topical insecticide)
Malathion lotion (overnight, whole body - washed off next day),
Benzyl benzoate (avoid in children)

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32
Q

what are the types of lice?

A

• Pediculus: capitis (head), corporis (body - can cause vagabond’s disease), phthirus pubis (pubic)

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33
Q

how do lice present?

A

intense itch

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34
Q

how are lice treated?

A

malathion lotion

35
Q

what skin diseases are caused virally?

A

chicken pox

neonatal VZV

shingles

herpes simplex virus

rasmay-hunt syndrome

erythema multiforme

molluscum contagiosum

warts HPV

36
Q

what is chickenpox?

A

caused by the varicella zoster virus (varicella) it is a primary infection normally during childhood

37
Q

how does chicken pox present?

A

general rash fever affects sensory nerve roots - ich macules which become papules which then become vesicles - lead to scabs and then recover virus establishes latency

38
Q

potential complications of chickenpox

A

secondary bacterial infection pneumonitis haemorrhagic rash scarring enecphalitis more severe if extremes of age - adult chickenpox can cause varicella pneumonia

39
Q

how is chickenpox managed?

A

there is a vaccine but it is not routine in children in the UK used in susceptible healthcare workers

40
Q

what is neonatal VZV?

A

secondary to chickenpox in mother in late pregnancy higher mortality

41
Q

how is neonatal VZV prevented?

A

if mother has chickenpox late in pregnancy give her VZ immune globulin or aciclovir

42
Q

What is shingles?

A

caused by varicella zoster virus (zoster/herpes zoster) reactivation of the VZV unusally in old age - incidence and severity increased in the immunocompromised and the elderly - greater age = greater pain

43
Q

how does shingles present?

A

starts with tingling and pain erythema develops - then vesicles - then crusts dermatomal distribution scarring isn’t common

44
Q

what kind of pain does shingles have?

A

neuralgic pain if it goes beyond week 4 - this is called post herpetic neuralgia (usually in the elderly, has a trigeminal distribution)

45
Q

potential complication of shingles?

A

• Can affect ophthalmic (this can happen in children esp. if chickenpox in utero or if they become immunocompromised), maxillary and mandibular divisions of the trigeminal nerve

46
Q

how is shingles prevented?

A

• Vaccine which is routine in 70 yr olds

47
Q

what is ramsay-hunt syndrome?

A

Caused by varicella zoster virus (herpes zoster) Reactivation of VZV Also known as geniculate/otic herpes zoster

48
Q

how does ramsay-hunt present?

A

vesicles, pain in auditory canal and throat, facial (7th nerve) palsy, irritation of the 8th cranial nerve [vestibulocochlear] causes deafness, vertigo, tinnitus (hearing noises that are not caused by an outside source)

49
Q

what is herpes simplex virus?

A

50% will have it before they’re adults, can be asymptomatic - usually in pre-school children

50
Q

how does herpes simplex virus present?

A

primary gingivostomatitis, extensive ulceration in and around the mouth, lasts around a week, can get recurrent, blistering rash at vermilion border (border between lips and skin) Herpetic whitlow = when is spreads to the fingers Eczema herpeticum = can be life-threatening

51
Q

what are the 2 types of herpes simplex virus?

A

HSV type 1 - main cause of oral lesions - can cause genital herpes and encephalitis HSV type 2 - especially occurs in neonates, can cause genital herpes and encephalitis

52
Q

How is HSV treated?

A

aciclovir

53
Q

What is erythema multiforme?

A

caused by drug reactions and some infections (HSV, mycoplasma pneumoniae bacterium)

54
Q

How does erythema multiforme present?

A

target lesions with erythema

55
Q

what is molluscum contagiosum?

A

it is common in children can also be sexually transmitted (appears around the genitals)

56
Q

how does molluscum contagiosum present?

A

fleshy firm umbilicated pearlescent nodules (1-2mm diameter)

57
Q

How is mollusum contagiosum treated?

A

self-limiting (takes months to disappear) can be treated with local application of liquid nitrogen

58
Q

what are warts?

A

caused by human papilloma virus (HPV) called verrucas if on feet a wart is an infection of keratinocytes - skin barrier is damaged in people with warts

59
Q

who gets warts?

A

common in children can be sexually transmitted

60
Q

how are warts treated?

A

self-limiting but can use topical salicyclic acid

61
Q

types of HPV

A

80 different types of HPV HPV 6 and 11 = genital warts HPV 16 and 18 = cervical cancer (there is now a vaccine for this)

62
Q

what is herpangina?

A

caused by enterovirus

63
Q

how does herpangina present?

A

blistering rash of back of mouth

64
Q

how is herpangina managed?

A

Self-limiting swab of lesion and sample of stool for enterovirus PCR

65
Q

what is hand, foot and mouth disease?

A

Caused by enterovirus (esp. coxsackie) Typically children, usually have family outbreaks

66
Q

What is erythema infectiosum?

A

aka slapped cheek caused by parovirus B19

67
Q

what complications does erythema infectiosum cause?

A

Commonly causes acute arthritis (esp. in wrists) as the rash fades (esp. in adults)

68
Q

what are the complications of parovirus B19?

A

Spontaneous abortion Aplastic crises (sudden drop in haemoglobin) Chronic anaemia

69
Q

how is erythema infectiosum diagnosed?

A

antibody testing (parvovirus B19 IgM test)

70
Q

what is orf?

A

scabby mouth which is caused by sheep virus it is on the hands of farmers

71
Q

how does orf present?

A

firm fleshy nodules on the hands self-limiting condition with a clinical diagnosis

72
Q

what is syphilis?

A

it is due to an STI - bacterial infection Treponema pallidum more common in male-male sex

73
Q

how does syphilis present?

A

Primary infection: chancre (painless ulcers, genitals and mouth) Secondary phase of infection: red rash over body (prominent on soles of feet and palms of hand), mucous membrane ‘snail track’ ulcers) Tertiary: CNS and cardiovascular involvement, gummatous (non cancerous tumour specific to syphilis)

74
Q

how is syphilis diagnosed?

A

blood test swab of chancre for PCR

75
Q

how is syphilis treated?

A

injections of penicillin

76
Q

what are the potential complications of syphilis?

A

pulsatile chest swelling

77
Q

what is lyme disease?

A

Bacterial infection (Borrelia burgdorferi), the vector is ticks

78
Q

how does lyme disease present?

A

Early = erythema migrans (look up pic) Late = heart block, nerve palsies, arthritis

79
Q

how is lyme disease treated?

A

amoxicillin or doxycycline

80
Q

what is the zika virus?

A

1 in 5 people infected with zika get ill Caused by Aedes aegypti (yellow fever mosquito) Usually tropical countries (endemic), can be sexually transmitted

81
Q

how does the zika virus present?

A

similar to dengue and chikungunya infection (both of which are also caused by the yellow fever mosquito), mild fever, maculopapular rash (flat, red area covered with small confluent bumps), headaches, arthralgia, myalgia, non-purulent conjunctivitis

82
Q

what are the potential complications of zika virus?

A

severe disease which requires hospitalisation or is fatal is rare microcephaly (head smaller than normal) Guillain Barre syndrome (autoimmune, attacks healthy nerve cells in the PNS)

83
Q
A

Charis & Ellie vs Dermatology (26 decks)

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