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2MB Dermatology > Microbiology > Flashcards

Microbiology Flashcards

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Dermatology Board Prep flashcards
1
Q

Define ‘virulence’

A

The ability of an organism to cause disease within a host

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2
Q

Name 5 virulence factors

A 
Adhesin
Impedin
Invasin
Aggressin
Modulin
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3
Q

What are adhesins?

A

Bacterial cell surface components that help the organism stick/adhere to host tissue

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4
Q

What are invasins?

A

Enable organisms to invade host tissue

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5
Q

What are impedins?

A

Help the organism avoid the defence/immune response in host tissue

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6
Q

What are aggressins?

A

Cause direct damage to host tissue + immune cells, affecting the host’s ability to cope with disease in the future

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7
Q

What are modulins?

A

Cause indirect damage to the host by turning the immune system in on itself (host’s immune system causes damage to host tissue)

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8
Q

The nasal strain of Staph. aureus can protect the mucosa. True/False?

A

True

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9
Q

Staph. epidermidis can occupy up to 100% of our skin. True/False?

A

True

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10
Q

Where is the most common entry of Staph. aureus into the body?

A

Nasal entry

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11
Q

Name the 3 particularly important virulence factors of Staph. aureus disease

A

Fibrinogen-binding protein (adhesin)
Leukocidin (kills leukocytes)
TSST-1 (toxin)

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12
Q

Every strain of Staph. aureus carries every virulence factor. True/False?

A

False

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13
Q

Which 2 severe skin diseases is leukocidin associated with?

A

Necrotising fasciitis

Recurrent furunculosis

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14
Q

Leukocidin is more virulent in hospital-acquired MRSA than community-acquired. True/False?

A

False

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15
Q

Give an example of a superantigen released by MRSA

A

TSST-1 (toxic shock)

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16
Q

How exactly do superantigens avoid specific T-cell activation?

A

Bind to MHC II complex on the outside, i.e. not the conventional binding groove

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17
Q

Name 3 skin infections caused by Strep. pyogenes

A

Impetigo
Cellulitis
Necrotising fasciitis

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18
Q

How does the Lancefield system classify different subtypes of Step. pyogenes?

A

M-protein

M1 and M3 are predominant; M3 and M18 cause severe, invasive disease

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19
Q

Which 2 virulence factors are particularly important as adhesins for Strep. pyogenes disease?

A 
Hyaluronic acid (sticky capsule)
CD44 +ve keratinocytes
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20
Q

The bigger the capsule, the less virulent an organism is. True/False?

A

False

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21
Q

Where does impetigo usually affect?

A

Face

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22
Q

Where in the body is Strep. pyogenes normally found?

A

Throat (pharynx)

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23
Q

Which strain of Staph aureus commonly produces abscesses and boils, usually affecting numerous family members at once?

A

PVL (panton valentine leukocidin)

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24
Q

Which group of Strep causes throat and severe skin infections?

A

Group A

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25
Q

Which bacteria cause impetigo?

A

Staph aureus

Group A Strep (step pyrogenes)

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26
Q

Which bacteria tends to cause nectrotising fasciitis?

A

Group A Strep (pyogenes)

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27
Q

What is the treatment of choice for Staph aureus?

A

Flucloxacillin

MRSA- doxycycline, vancomycin

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28
Q

What is the treatment of choice for Strep pyogenes?

A

Penicillin or flucloxacillin

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29
Q

What is necrotising fasciitis?

A

Bacterial infection spreading under the skin into fascia

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30
Q

What is the nickname of necrotising fasciitis?

A

Flesh-eating bacterial disease

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31
Q

Type I necrotising fasciitis is caused by Group A Strep. True/False?

A

False
Type I = mixed anaerobes and coliforms
Type II = group A Strep

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32
Q

What is the most common skin fungal infection caused by?

A

Ringworm (Tinea)

33
Q

Tinea pedis is another name for what?

A

Athlete’s foot

34
Q

How is dermatophyte (Fungal) infection caused?

A

Fungus enters abraded skin and infects keratinised tissue, provoking inflammation and outward lesioning
Increased epidermal turnover (scaling) and inflammatory response

35
Q

Which organism is the most common cause of dermatophyte infection?

A

Trichophyton rubrum

36
Q

How are small areas of dermatophyte infection treated?

A

Clotrimazole cream

Nail paint

37
Q

How are dermatophyte scalp infections treated?

A

Terbinafine oral

Itraconzole oral

38
Q

Which parasite causes scabies?

A

Sarcoptes scabiei

39
Q

Incubation of the scabies parasites takes up to how long?

A

6 weeks

40
Q

How is scabies treated?

A 
Malathion lotion overnight
Benzyl benzoate (not in children)
41
Q

Chickenpox and shingles are due to which virus?

A

Varicella zoster

42
Q

Where does varicella zoster become dormant following chickenpox?

A

Dorsal root ganglia of spine

43
Q

Chickenpox can cause pneumonitis and encephalitis. True/False?

A

True

44
Q

What is Ramsay-Hunt syndrome?

A

Reactivation of VZV in CN VII

Causes vesicles and pain in auditory canal and throat

45
Q

What does herpes simplex virus cause around the mouth?

A

Primary gingivostomatitis

Extensive ulceration

46
Q

What is the treatment of choice for varicella zoster and herpes simplex virus?

A

Aciclovir

47
Q

Which virus tends to cause warts?

A

Human papilloma virus

48
Q

Which treatment is effective for warts?

A

Salicylic acid

49
Q

Which bacterium causes syphilis?

A

Treponema pallidum

50
Q

How is syphilis treated?

A

Penicillin injections

51
Q

Is staph aureus coagulase positive or negative?

A

Positive

52
Q

What is the mode of action of capsule virulence factor?

A

Antiphygocytic

53
Q

What is the mode of action of fibrogen binding protein virulence factor?

A

Adhesin

54
Q

What is the mode of action of hawmolysins virulence factor?

A

Cytolytic (erythrocytes)

55
Q

What is the mode of action of coagulase virulence factor?

A

Clots plasma

56
Q

What is the mode of action of fibrinolysin virulence factor?

A

Digests fibrin

57
Q

What is the mode of action of leukocidin (PVL) virulence factor?

A

Kills leukocytes

58
Q

What is the mode of action of hyaluronidase virulence factor?

A

Hyaluronic acid (ECM)

59
Q

What is the mode of action of protein A virulence factor?

A

Antiphagocitic

60
Q

What is the mode of action of epidermolytic toxins A&B virulence factor?

A

Epidermal splitting/exfoliation

61
Q

What is the mode of action of enterotoxin virulence factor?

A

Vomiting and diarrhoea

62
Q

What is the mode of action of TSST-1 virulence factor?

A

Shock rash and dequamation

63
Q

Where does tinea capits effect?

A

Scalp

Mainly in children

64
Q

What is candida skin infection?

A

Seen in skin fold areas

‘Warm and moist’ areas

65
Q

What is the treatment for candida skin infection?

A

Clotrimazole cream

Oral fluconazole

66
Q

What is scabies and where does it occur?

A

Itchy rash

Affecting finger webs, wrists and genital areas

67
Q

How does chicken pox present?

A

Fever and itch
Macules> papules > vesicles > scabs > recovery
Dangerous in elderly/immunocompromised

68
Q

How does shingles present?

A

Reaction of virus down one dermatome
Erythema> vesicles > crusts
More likely in elderly or immunocompromised
Tingling and pain

69
Q

What happens when shingles last more than 4 weeks?

A

Post herpetic neuralgia

70
Q

What is type 1 HSV?

A

Main cause oral, half genital

71
Q

What is type 2 HSV?

A

Rare cause oral, half genital

72
Q

What is HPV?

A

Causes viral warts, genital warts, cervical cancer

73
Q

What is the treatment for warts in HPV?

A

Salicylic acid

Cryotherapy

74
Q

What is the most common causative organism for tinea?

A

Trichophyton rubrum

75
Q

What does tinea have a ring appearance?

A

Heals from the inside out

76
Q

What is the management for tinea?

A

Small areas- clotrimazole cream

Scalp- oral tebinafine, itraconzole

77
Q

What is the treatment for scabies?

A

Permethrin- 1st line treatment

Malathion lotion- 2nd line treatment

78
Q

How does Lyme disease appear?

A

The rash has a characteristic ‘bull’s-eye’ appearance and usually presents 1-2 weeks after the tick bite

79
Q

What is treatment for Lyme disease?

A

Oral Doxycycline

2MB Dermatology (13 decks)

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