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Dermatology Week 2 2017/18 > 3: Microbiology - bacterial and fungal skin infections > Flashcards

3: Microbiology - bacterial and fungal skin infections Flashcards

1
Q

What does sebum contain which lends towards its antibacterial properties?

A

Fatty acids

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2
Q

Name three species of bacteria which live on the skin.

A

Staph. epidermidis

Corynebacterium spp.

Propionibacterium spp.

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3
Q

What is a boil / furuncle?

A

A deep folliculitis - infection of the hair follicle

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4
Q

What can be used to identify the organism responsible for a skin infection?

A

Swab

Blood cultures if appropriate

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5
Q

Which test is used to differentiate different species of Staphylococcus?

A

Coagulase test

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6
Q

How do Staph. aureus appear on a coagulase test?

A

Golden

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7
Q

How does Staph. epidermidis appear on a coagulase test?

A

White

(Coagulase negative)

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8
Q

Which species of Staphylococcus appear white on a coagulase plate?

A

More than 20, including epidermidis, all referred to as “Coagulase negative Staph.”

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9
Q

How do Staphylococci appear under the microscope?

A

Gram positive clusters of round cocci

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10
Q

Which organism is usually responsible for cellulitis (i.e skin infections)?

A

Staph. aureus

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11
Q

Why aren’t coagulase negative organisms (e.g Staph. epidermidis) considered more seriously if found on a swab?

A

Commensals found on the skin

Sometimes they cause infection (e.g infective endocarditis in prosthetic valves) but usually not

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12
Q

Are Staphylococci Gram positive or Gram negative?

A

Gram positive (appear dark purple when Gram stained)

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13
Q

The coagulase test is used to differentiate different species of Staphylococci. Which test is used for Streptococci?

A

Haemolysis

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14
Q

Streptococci appear in (chains / clusters) and are Gram (positive / negative).

A

chains

Gram positive

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15
Q

Which species of Streptococci are alpha haemolytic?

Which colour do they turn on the plate?

A

Strep. pneumoniae

Strep. “viridans”

Green

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16
Q

Which cardio condition are Strep. viridans often involved in?

A

Endocarditis

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17
Q

Alpha haemolysis is also known as ___ haemolysis.

A

partial

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18
Q

Which species of Streptococci are beta haemolytic?

What colour do they turn on the plate?

A

Group A and B Strep.

Yellow

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19
Q

What is beta haemolysis also known as?

A

Complete haemolysis

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20
Q

Which species of Strep. is the one synonymous with Group A Strep?

A

Streptococcus pyogenes

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21
Q

Gamma haemolysis is also known as __ haemolysis.

A

no

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22
Q

Which species of Streptococci are non-haemolytic?

A

Enterococci - bowel commensals

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23
Q

Give 1) the type of haemolysis and 2) the colour change on the plate for each of these bacteria:

Strep. pyogenes

Strep. pneumoniae

Strep. agalactiae (Group B)

Strep. viridans

Enterococcus spp.

A

Strep. pyogenes (A) - Beta haemolytic - Yellow

Strep. pneumoniae - Alpha haemolytic - Green

Strep. agalactiae (B) - Beta haemolytic - Yellow

Strep. viridans - Alpha haemolytic - Green

Enterococcus - Non-haemolytic - No change

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24
Q

What is another species of Coagulase negative Staph., excluding epidermidis?

A

Staph. saprophyticus

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25
Q

Which species of Staph. is responsible for wound, skin, bone and joint infections?

A

Staph. aureus

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26
Q

Why is Staph. aureus so virulent?

A

Produces loads of enzymes

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27
Q

What is the drug of choice for treating Staph. aureus infections?

What is the exception?

A

Flucloxacillin

If it’s methicillin resistant i.e MRSA

28
Q

What are some toxins produced by Staph. aureus?

A

Enterotoxin - food poisoning

SSSST - Staphylococcal scalded skin syndrome toxin

PVL - Pantol Valentine Leucocidin (comes up in exams)

29
Q

Name some skin infections Staph. aureus is commonly responsible for.

A

Boils and carbuncles (clusters of boils)

Cellulitis

Infected eczema

Impetigo

SSST

30
Q

What drugs can be used instead of fluxcloxacillin to treat MRSA?

A

Doxycycline

Co-trimoxazole

Clindamycin

Vancomycin

31
Q

Coagulase negative organisms like Staph. epidermidis are usually (commensal / pathogenic).

A

commensal

32
Q

When may Staph. epidermidis cause infection?

A

Artificially implanted stuff like pacemakers, joints, heart valves, catheters…

33
Q

What kind of infection does Staph. saprophyticus tend to cause?

A

UTIs in women

34
Q

Streptococci are Gram positive organisms commonly found in (clusters / chains).

A

chains

35
Q

Name an enzyme produced by beta-haemolytic Strep. which damages tissues.

A

Haemolysin

36
Q

What are some skin infections caused by Strep. pyogenes i.e Group A Strep.?

A

Infected eczema

Impetigo

Cellulitis

Erysipelas (superficial dermatitis on face, upper & lower limbs)

NECROTISING FASCIITIS

37
Q

What life-threatening condition is caused by Group A Strep**.?

A

Necrotising fasciitis

38
Q

What is the antibiotic of choice for treating Staph. aureus infections?

A

Flucloxacillin

39
Q

What is the antibiotic of choice for treating Strep. pyogenes (Group A) infections?

A

Penicillin / Flucloxacillin

40
Q

In addition to giving penicillin, what needs to be done for a patient with necrotising fasciititis?

A

Immediate removal of affected tissue

41
Q

Although there is little to see on the skin itself, what is the main symptom of necrotising fasciitis?

Why?

A

Severe pain

Infection is spreading along the fascia, destroying all the tissue

42
Q

A leg ulcer tends to be a ___ problem only.

A

vascular

i.e you don’t need to give antibiotics

43
Q

What investigation should be carried out if a leg ulcer looks infected?

A

Swabs

44
Q

What drug should you add to fluclox/penicillin if you suspect that there are anaerobes in a diabetic foot ulcer?

A

Metronidazole

45
Q

What kind of infection is ringworm?

A

Fungal infection

46
Q

What does tinea mean?

A

Ringworm

47
Q

Where is tinea capitis found?

A

Scalp

48
Q

Where is tinea barbae found?

A

Beard

49
Q

Where is tinea corporis found?

A

Body

50
Q

Where is tinea manuum found?

A

Hands

51
Q

Where is tinea unguium found?

A

Nails

52
Q

Where is tinea cruris found?

A

Groin

53
Q

Where is tinea pedis found?

What is this infection also known as?

A

Feet

Athlete’s foot

54
Q

What is the fungus responsible for 70% of ringworm infections?

A

Trichophyton rubrum

55
Q

How is ringworm infection diagnosed?

A

By examination +/- Wood’s lamp

Nail/hair/skin shavings sent for microscopy and culture

56
Q

What is used to treat small fungal infections on the hair or nails?

A

Clotrimazole cream (Candesan)

Amorolfine nail paint

57
Q

What is used to treat fungal scalp infections?

A

Terbinafine orally

Itraconazole orally

58
Q

Where do Candida. infections tend to be seen?

A

Warm, moist areas - breasts, groin areas, skin folds, nappy area

59
Q

How is Candida. infection diagnosed?

A

Swabs > Culture

60
Q

What is given to treat Candida infections?

A

Clotrimazole cream (Cantesan)

Oral fluconazole i.e antifungals

61
Q

What is scabies?

A

Itchy rash on fingers, wrists and genitals

62
Q

What is the chronic, crusty form of scabies called?

A

Norwegian scabies

63
Q

What is the organism causing scabies?

A

Sarcoptes scabiei

64
Q

What are some treatment options for scabies?

A

Malathion lotion

Benzyl benzoate

65
Q

What else is treated with malathion lotion?

A

Lice

Dermatology Week 2 2017/18 (8 decks)

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