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Year 2: Dermatology > Dermatology Microbiology > Flashcards

Dermatology Microbiology Flashcards

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Dermatology Board Prep flashcards
1
Q

define “boil” (AKA furuncle)

A

a deep folliculitis (infection of a hair follicle). Most commonly caused by bacterium staph aureus - resulting in a painful swollen area on the skin caused by accumulation of pus and dead tissue.

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2
Q

define carbuncle

A

carbuncle = individual boils clustered together

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3
Q

staph aureus is Gm___ and shape is ___

A

Gm+ve, shape is circles clustered together (like a bunch of grapes)

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4
Q

name some coagulase -ve staph

A

staph epidermidis

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5
Q

staph aureus is coagulase ____

A

+ve - so staph aureus can clot blood and protect itself from phagocytosis by coating itself with fibrin clot

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6
Q

give some examples of alpha haemolytic (partial haemolysis) strep

A 
strep pneumonia (pneumonia)
strep viridans (commensals, endocarditis)
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7
Q

give some examples of beta haemolytic (complete haemolysis) strep

A

Group A strep (throat, skin infection)
Group B strep (neonatal meningitis)
Group C, G etc

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8
Q

give some examples of gamma (non-haemolytic) strep

A

Enterococcus sp. (gut commensal, UTI)

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9
Q

what is the usual antibiotic to use in staph aureus infection?

A

flucloxacillin (works in MSSA)

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10
Q

can flucloxacillin be used in MRSA?

A

no. MRSA is methicillin resistant = and therefore resistant to flucloxacillin

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11
Q

what does the SSSST (staph scalded skin syndrome toxin) do?

A

causes desmoglein 1 within the epidermis to break up so skin becomes unstuck - looks like burns

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12
Q

what does the Panton Valentine Leukocidin do?

A

its presence is associated with increased virulence of certain strains of staph aureus. It’s present in most MRSA, causes necrotic lesions including haemorrhagic pneumonia. PVL creates pores in membranes of infected cells

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13
Q

list some defence mechanisms of the skin

A

intact skin is barrier to infection
surface is dry so dessicates microorganisms
sebum is fatty acids and so inhibits bacaterial growth
competitive bacterial flora
concept of resident and transient flora

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14
Q

list some skin infections that staph aureus can cause

A 
boils and carbuncles
minor skin sepsis (infected cuts etc)
cellulitis
infected eczema
impetigo
wound infection
staphylococcal scalded skin syndrome
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15
Q

which skin layer(s) does impetigo affect?

A

the epidermis

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16
Q

which skin layer(s) does erysipelas affect?

A

upper dermis

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17
Q

which skin layer(s) does cellulitis affect?

A

lower dermis and subcutaneous tissue

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18
Q

which skin layer(s) does necrotising fasciitis affect?

A

subcutis and deep fascia

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19
Q

what is the antibiotic of choice for strep pyogenes infection (group A strep)?

A

penicillin

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20
Q

what does necrotising fasciitis need in addition to antibiotics?

A

surgical debridement

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21
Q

when should leg ulcers be swabbed for microbiology?

A

ONLY when infection is suspected (e.g. looks sloughy and dirty, or has clinical signs of infection)

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22
Q

dermatophyte infection (ringworm) is a parasitic/ fungal infection?

A

fungal. Tinea is named depending on the part of the body affected

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23
Q

what is the classic appearance of tinea?

A

concentric rings of red scaliness, often healed in the middle

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24
Q

what is the common name for tinea pedis?

A

athlete’s foot

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25
Q

can dermatophyte infection ever enter the bloodstream?

A

NO it only infects keratinised tissues (hair, skin, nails)

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26
Q

how can ringworm be diagnosed?

A

clinical appearance
Wood’s light
skin scrapings, nail clippings, hair (culture takes 2 weeks) - may just want to confirm that it really is a fungal infection

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27
Q

what treatment is used for uncomplicated (e.g. just infecting the skin) ringworm?

A

topical clotrimazole

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28
Q

what treatment can be used for complicated (nail) ringworm?

A

oral terbinafine

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29
Q

what are treatments for candida infection?

A

clotrimazole cream, oral fluconazole

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30
Q

what is Norwegian scabies?

A

many many scabies mites. occurs in people who are immunocompromised

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31
Q

how long do scabies mites survive away from the human body?

A

3 days

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32
Q

what is the preferred treatment for scabies?

A

malathion lotion (washed off after a day) (benzyl benzoate is an alternative)

33
Q

what are possible treatments for head lice and body lice?

A

malathion lotion and benzyl benzoate

34
Q

which virus is the cause of both chickenpox and shingles?

A

varicella zoster virus

35
Q

chickenpox is AKA _____

A

varicella

36
Q

shingles is AKA ______

A

zoster

37
Q

what is the progression of chickenpox skin lesions like?

A

macules - papules - vesicles - scabs - recovery

there is also fever and itch

38
Q

what are some possible complications of chickenpox?

A

secondary bacterial infection, pneumonitis, haemorrhagic, scarring, encephalitis (if it spreads to brain)

39
Q

a bad sign in chickenpox is a haemorrhagic rash. The rash will look like purpuric confluent lesions. What is the significance of this?

A

these people often have low platelets

40
Q

neonatal VZV can occur secondary to chickenpox in the mother in late pregnancy. This has a lower/ higher mortality for the baby?

A

higher mortality

41
Q

how can chickenpox be prevented in susceptible pregnancy women who have been in contact with chickenpox?

A

administer the varicella zoster immune globulin

42
Q

what is the progression of the skin lesions like in shingles?

A

tingling/ pain - erythema - vesicles - crusts
(the pain is neuropathic, very sharp, and may present before the rash appears)
shingles is distinctive due to the dermatomal distribution

43
Q

what is a complication of shingles (apart from scarring)?

A

post-herpetic neuralgia (this is when the pain lasts for more than 4 weeks)
(this is more likely in the elderly, and if the person has trigeminal dermatome shingles)

44
Q

with ophthalmic shingles, why should the patient be urgently referred to an ophthalmologist?

A

they are at risk of keratitis (inflammation of the cornea)

45
Q

what is Ramsay-Hunt syndrome type 2?

A

disorder caused by reactivation of VZV in the geniculate ganglion - a nerve cell bundle of the facial nerve. Typically presents with inability to move many facial muscles, pain in ear, taste loss on front of tongue, dry eyes, vesicular rash.
(May also have CNVIII irritation - causing deafness, vertigo, tinnitus)

46
Q

is there a vaccine for chickenpox?

A

yes, but nod widely used for UK children, used in UK for susceptible healthcare workers

47
Q

is there a vaccine for shingles?

A

yes, different from chickenpox one because it is in a very high titre. Giving it to old people (who have already had chickenpox in childhood) boosts their immune reactions to VZV. Need it just once. It also reduces incidence of post-herpetic shingles.

48
Q

describe the illness that herpes simplex virus (HSV) causes in pre-school children?

A

primary gingivostomatitis
extensive ulceration around mouth, lasts around a week
Most will be asymptomatic

49
Q

herpes simplex virus undergoes latency in the dorsal root ganglion (just like VZV does). When it recurs, what is the illness like?

A

outbreaks of coldsores (can spread to eczema and cause eczema herpeticum)
mostly just need treated at home, but some children need hospitalized to be rehydrated because it hurts them to eat and drink
unlike VZV, you can get multiple reactivations throughout life

50
Q

there are 2 types of herpes simplex virus. Type 1 and Type 2. Half of genital lesions are caused by each one. But which one is the main cause of oral lesions?

A

HSV type 1

51
Q

what is the treatment for VZV and HSV?

A

acyclovir (which is a guanosine analogue)

52
Q

how can viral diseases be diagnosed by investigation?

A

send swab in viral transport medium to lab for lab for PCR to detect genetic material for the virus.
OR if site inaccessible - can do Ig tests (but swabs are better overall)

53
Q

what is erythema multiform caused by?

A

it’s a hypersensitivity reaction usually triggered by infections, most commonly herpes simplex virus (also e.g. mycoplasma pneumonia). It is acute, self-limiting, usually resolves without complications.

54
Q

what is molluscum contagiosum?

A

fairly common viral infection of the skin that results in small, raised, ink lesions with a dimple in the centre, may be itchy or sore. Due to a poxvirus called the molluscum contagiosum virus, which is spread through direct contact e.g. sexual activity/ shared towels. Self-limiting but takes months to disappear - can be treated with liquid nitrogen. Otherwise asymptomatic.

55
Q

warts (on hands and feet) are usually caused by HPV. Which types of HPV cause these warts?

A

type 1 to 4

56
Q

describe the condition of HPV warts (called verrrucas if on feet)?

A

self-limiting, common in children, will eventually resolve on their own. Can treat with topical salicylic acid.

57
Q

what types of HPV cause genital warts?

A

types 6 and 11

58
Q

what types of HPV cause cervical cancer?

A

16 and 18

59
Q

which types of HPV virus are protected against by the HPV vaccine?

A

6, 11, 16, 18

60
Q

what is herpangina?

A

painful mouth and throat ulcers due to a self-limited viral infection, usually in childhood. Caused by enterovirus (not herpes virus - despite the name), spread via faecal-oral route. Fever is first sign, general malaise, sore throat, odynophagia.
Can swab a lesion/ get a stool sample for enterovirus PCR.

61
Q

how can herpangina be distinguished from hand, foot and mouth disease?

A

in herpangina, there is lack of skin lesions (whereas there ARE skin lesions in hand, foot and mouth)

62
Q

what is hand, foot and mouth disease?

A

It’s a common and short-lasting viral infection caused by enteroviruses, typically in children. There are blisters on hands, feet and mouth. rarely affects adults.
Small vesicles and ulcers around the mouth can be painful - so child might not eat much.
Infection spread by direct skin, nasal/ oral secretion contact, or faecal contamination

63
Q

what is the treatment for hand, foot and mouth disease?

A

specific treatment NOT needed.
DON’T rupture blisters (to reduce contagion), keep blisters clean, use non-adherent dressings on erosions, maintain adequate fluid intake (IV fluids may be needed if oral intake poor due to painful erosions), antiseptic mouthwashes (to relive ulcers)

64
Q

describe erythema infectiosum (AKA slapped cheek disease)?

A

caused by parvovirus B19, slapped cheek appearance, as the facial rash fades, a lacy macular rash appears on body. In adults the rash may be absent and an acute polyarthritis of the small joints may be prominent.
Children with it look and feel quite well - adults get the worse effect of arthritis.
The parvorirus 19 targets RBCs in the bone marrow. Spread via respiratory droplets. First, get non specific symptoms and then the red cheeks (which feel burning hot). Lasts 2-4 days. Rashes can persist up to 6 weeks. No specific treatment, apply ice-cold flannel to cheeks to relieve discomfort.

65
Q

what are possible complications of parvovirus 19 (the virus which causes erythema infectiosum AKA slapped cheek disease)?

A 
spontaneous abortion
aplastic crisis (sudden Hb drop, seen in patients with short RBC lifespan e.g. thalassaemia, sickle cell anaemia)
chronic anaemia (in immunosuppressed patients)
66
Q

how can infection with parvovirus 19(the virus which causes erythema infectiosum AKA slapped cheek disease) be confirmed in the lab?

A

by Ig testing (NOT skin swabs, but a BLOOD test)

testing for IgM

67
Q

what is rubella?

A

infection caused by rubella virus, often mild, with half of people not even realising they are sick, rash may start and last for about 3 days, usually starts on face and spreads to rest of body. Swollen lymph nodes are common and may last a few weeks. Fever, sore throat, and fatigue may also occur. Joint pain common in adults. Rubella is spread through cough droplets of infected people. Can be prevented by MMR vaccine. Rubella can cause birth defects if a pregnant woman is infected.

68
Q

what is Orf?

A

cause by parapox virus and occurs primarily in sheep and goats contact. Causes papules that can persist for 7-10 weeks and spontaneously resolves. Uncommon and difficult to diagnose. Self-limiting. Clinical diagnosis, lab confirmation not used.

69
Q

what is syphilis?

A

illness due to STI with Treponema pallidum (which is a bacterium)

70
Q

what is the primary phase of syphilis like?

A

there is a chancre (painless ulcer), which lasts about 21 days after initial Treponema pallidum infection. Chancres transmit the sexually transmitted disease of syphilis through direct physical contact. If not diagnosed then, the chancre goes away and the patient may get secondary / tertiary syphilis.

71
Q

what is the secondary phase of syphilis like?

A

red rash over body, prominent on soles of feet and palms, mucous membrane “snail track” ulcers. Untreated, the infection may go on to the tertiary phase.

72
Q

what is the tertiary phase of syphilis like?

A

CNs, gummatous (granulomas in any organ), CVS disease etc…

73
Q

how is syphilis diagnosed?

A

blood test/ swab of chancre for PCR

74
Q

how is syphilis treated?

A

injections of penicilin

75
Q

who is syphilis more common in - men or women?

A

men (10x)

76
Q

what is Lyme disease?

A

disease caused by bacterium called Borrelia burgdorferi. Contracted from ticks - the tick has to be attached for 24 hours in order for infection to occur.
Early signs: erythema migrans (bull’s eye rash) is diagnostic and doesn’t need lab confirmation. Late: heart block, nerve palsies, arthritis.
Treat IMMEDIATELY with doxycycline. or amoxicillin
Lab confirmation is mainly for late presentations and is a blood test for Ig to organism

77
Q

what is measles?

A

highly contagious infection caused by measles virus. Initial signs and symptoms are high fever, runny nose, inflamed eyes. Small spots form inside mouth (Koplik’s spots). Spread through coughs and sneezes.

78
Q

what is Zika virus?

A

virus spread by mosquitoes. Get mild fever, rash, headaches, arthralgia, myalgia. Can pass from mother to unborn baby - causing CNS problems and micrcephaly. Also, men can harbour the virus in their semen for up to 6 months.

Year 2: Dermatology (11 decks)

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