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MCD Microbiology > Skin Infections > Flashcards

Skin Infections Flashcards

(78 cards)

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1
Q

what are the features of staphylococcus aureus?

A
  • gram +ve
  • commensal in 30% of humans in nose, axilla and groin
  • most common bacteria cause of skin infection
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2
Q

what are the 5 manifestations a skin staph aureus infection?

A 
- impetigo
 (and bullous (blistering) impetigo
- folliculitis
- ecthyma
- boils
- carbuncles
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3
Q

what is impetigo?

A

infection of subcorneal (strata corneum) layer of epidermis

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4
Q

what is folliculitis?

A

infection at the mouth of the hair follicle (at top)

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5
Q

what is ecthyma?

A

infection of full thickness the epidermis creating a thick adherent scar at necroses site

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6
Q

what is a boil?

A

abscess of the hair follicle spanning the epidermis and dermis

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7
Q

what is a carbuncle?

A

abscess of several adjacent hair follicles

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8
Q

what are the toxins (virulence factors) produced by staph aureus?

A
  • Panton Valentine Leuocidin
  • Exfoliative toxin
  • TSST-1 (Toxic Shock Syndrome Toxin 1)
  • Enterotoxin
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9
Q

what disease does the exfoliative toxin cause?

A

Staphylococcal Scalded Skin Syndrome (in children less than 5 yrs- version of bullous impetigo)

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10
Q

what disease does TSST-1 cause?

A

Toxic shock Syndrome

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11
Q

what disease does enterotoxin cause?

A

diarrhoea, food poisoning

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12
Q

what disease does Panton Valentine Leuocidin cause?

A

toxin of staph aureus:

Necrotising soft tissue infections

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13
Q

how are staph aureus infections of the skin normally treated?

A

antibiotics (no vaccine)

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14
Q

how does the exfoliative toxin lead to bullous impetigo?

A

splitting of the skin leads to pus filled blisters

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15
Q

describe how impetigo looks like on skin

A

golden and crusty
common in children
around the mouth and face

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16
Q

what type of bacteria is Treponema pallidum? what disease does it cause?

A

gram -ve
causes syphillis (STI)
- enhances HIV transmission

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17
Q

what are the stages of a syphillis infection? what are the features of disease at each stage?

A

1) Primary (3-8 weeks)
– painless ulcers (chancre) at site of inoculation.

2) Secondary (6-12 weeks)
– disseminated infection, rapid proliferation, with rash (maculopapular on palms and soles), condylomata lata and lymphadenopathy.

3) Latent
– asymptomatic period but still transmissible

4) Tertiary (years later)
– reactivated; gummatous skin lesions, bone lesions, , neurological and vascular manifestations e.g. thoracic aneurysm

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18
Q

What results in symphilis in an infant?

A

vertical transmission from the mother leads to congenital syphilis

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19
Q

what effect does syphilis have on a developing foetus?

A
  • stillbirth
  • miscarriage
  • prematurity
  • brain abnormalities
  • bone disease
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20
Q

how is syphilis treated?

A

antibiotics e.g. penicillin

no vaccine

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21
Q

what are some of the members of the herpes simplex virus family?

A

HHV1 –> HSV type 1
HHV2–> HSV type 2
HHV3–> VZV

HHV4–> EBV
HHV5–> CMV
HHV8–> Kaposi Sarcoma

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22
Q

what does Kaposi sarcoma affect?

A

endothelium of lymphatics

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23
Q

what does VZV cause?

A

chickenpox and shingles (herpes zoster)

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24
Q

what is common between HHV1 to 3?

A

are latent in nerves

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25
what type of infections do HSV type 1 and HSV type 2 cause?
type 1 causes oral infections | type 2 causes genital infections
26
what type of infections does HSV type 1 cause?
oral
27
what type of infections does HSV type 2 cause?
genital
28
how is HSV transmitted?
direct contact
29
what are the clinical features of a HSV infection?
- painful vesicular rash (heals over 2-4 weeks) - eczema herpeticum (eczema increases risk of herpes infection) - herpes encephalitis.
30
what causes the reactivation of HSV into the tertiary stage?
stress on the body e.g. infection
31
what is the treatment for HSV infection?
anti-viral medication such as acyclovir
32
what are the two stages of VZV infection?
- primary infection causes chicken pox | - reactivation causes VZV causes shingles/herpes zoster
33
what are the features of a primary infection with VZV?
chicken pox features: - prodrome of fever - malaise - followed by development of widespread vesicular rash concentrated on the face and trunk - oral lesions - mild in children, more serious in older children and adults - usually lasts ~2 weeks and then becomes latent.
34
what is the hallmark feature of a reactivated VZV infection?
in shingles, and a painful vesicular rash appears along the course of a dermatome e.g. CN V1 (ophthalmic division of trigeminal) on the top right of the face – usually heals in 2-4 weeks.
35
what is the treatment for VZV?
Vaccine is available and anti-viral medication can be given
36
where does VZV lay latent?
dorsal root ganglia
37
name two types fungi that cause superficial skin infections and give an example of the fungi
1) Dermatophytes (type of mould) e. g. Trichophytum rubrum 2) yeasts e. g. candida
38
where do dermatophytes grow?
in parts of the body with keratin therefore hair, skin and nails they grow as hyphae
39
what are the infections that dermatophytes cause?
"tinea": e. g. Tinea capitis – Kerion is a type of tinea capitis; occurs on the scalp esp on prepubertal, black kids e. g. Tinea manuum – dorsum of hand. e. g. tinea cruris – inner thigh region (Jock itch)
40
where do yeasts like candida grow?
grow in moist, humid places
41
what is the clinical manifestation of yeast infection?
eryhthromatous scaly rash on skin/scalp, discoloured or crumbly nails.
42
what is the treatment for superficial fungal skin infection?
topical or systemic anti-fungal medications such as Terbinafine
43
what is scabies?
A skin infestation by the mite Sarcoptes scabei.
44
how does the infestation of sarcoptes occur? what results after it has established itself in the skin?
- The mite burrows into the surface of the skin (stratum corneum) - Asymptomatic for first 4 weeks - Exposure to the mite faeces and eggs cause a delayed-type allergic reaction - Results in widespread eczematous rash occurring ~4 weeks after first infestation - A secondary bacterial infection is common e.g. strept --> glomuronephritis
45
where do sarcoptes mites burrow mostly?
genital regions, nipples, wrists, finger webs, instep of feet, axilla
46
how do you spot a mite burrow?
a squiggle with a black dot (head of mite)
47
how is scabies treated?
with topical systemic insecticides
48
how is scabies transmitted?
by skin-skin contact over longer periods (minutes)
49
what are the layers of the epdermis?
stratum corneum granular layer spinous layer basal layer then comes the dermis
50
what is cellulitis and what can cause this?
- staph aureus - acute, painful infection of deeper dermis and subcutaneous tissue - often due to break in skin from trauma or another infection
51
what causes Scalded skin syndrome?
- exotoxin of staph aureus - destroy keratinocyte attachments in stratum granulosum --> sloughing off of skin - seen in newborns and children
52
what bacteria causes syphilis?
treponema pallidum
53
what is the treatment for syphilis?
IM antibiotic : penicillin
54
what are the types of syphilis?
primary: lone, painless ulcer on the genitals secondary: - Condylama lata (gray-white wart like lesions of mucous membranes - Rash on palms/soles tertiary: - gummas (soft growths with necrotic centres)
55
what part of the body is HSV1 usually confined to?
the upper body (oral)
56
where does the HSV1 stay latent and then cause cold sores?
trigeminal ganglion
57
what causes reactivation of the latent HSV?
stress
58
what are the effects of HSV 1 infection?
- kertaoconjunctivitis - gingiviostomatitis (first sign) - erythema multiform (target lesion) - herpetic whitlow (painful hand vesicle)
59
what is the most common cause of sporadic temporal lobe encephalitis?
HSV1
60
what does temporal lobe encephalitis present with?
- seizures - aphasia - altered mental status
61
what part of the body is HSV2 confined to usually?
lower and upper ``` sex associated (therefore STI) urogenital ``` causes painful inguinal lymphadenopathy
62
where does HSV2 remain latent?
sacral ganglion
63
what are the diseases varicella zoster caused in children, adults and the elderly?
children and adults--> chicken pox elderly--> shingles
64
where does VZV in shingles remain latent?
dorsal root ganglia
65
what effect does the location of VZV latency have on the presentation of infection?
as it stays latent in the dorsal root ganglia there is a dermatomal distribution to the infection
66
what causes the reactivation of VZV in the elderly?
stress ageing immunocompromised state
67
what effect does shingles have after the rash has cleared?
can be extremely painful (post herpetic neuralgia)
68
why does shingles lead to involvement of the eye?
effect on trigeminal nerve
69
what are some tinea manifestations of trichophytum rubrum?
- rashes (tinea) - --> capitis (head) - --> corporis (body) - --> curries (groin) - -> pedis (foot)
70
why may scabies be worse at night?
type 4 hypersensitivity reaction
71
what layer of the skin does the sarcoptes scabei burrow into?
stratum cornium into webspace of hands and feet
72
skin disease epidemiology
In the UK: - approximately 15% of GP consultations are skin related - of those, 25% are due to a skin infections Skin infections are much more common in hot humid climates and amongst poor populations.
73
gram for Staph Aureus
+ colonisation in nose, axillae and groins.
74
what are the common skin infections caused by staph aureus?
``` impetigo folliculitis ecthyma boils carbuncles. ```
75
gram for treponema pallidum
- cause of syphillis
76
what are the stages of syphillis?
Primary : painless ulcer (chancre) at site of inoculation Secondary: disseminated infection with rash and lymphadenopathy Latent (asymptomatic) period Tertiary: skin, neurological and vascular manifestations
77
what type of nucleic acid in HSV
dsDNA
78
what disease does reactivation of VZV cause?
shingles (herpes zoster) - painful vesicular rash appears only along the course of a dermatome (sensory nerve) - serious eye consequences if the distribution of the Ophthalmic Division of the Trigeminal nerve is involved.

MCD Microbiology (6 decks)

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