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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
Which species of *Staph.* is responsible for wound, skin, bone and joint infections?
***Staph. aureus***
26
Why is *Staph. aureus* so virulent?
**Produces loads of enzymes**
27
What is the drug of choice for treating *Staph. aureus* infections? What is the exception?
**Flucloxacillin** If it's methicillin resistant i.e MRSA
28
What are some **toxins** produced by *Staph. aureus*?
**Enterotoxin** - food poisoning **SSSST** - *Staphylococcal* scalded skin syndrome toxin **PVL** - Pantol Valentine Leucocidin (comes up in exams)
29
Name some skin infections *Staph. aureus* is commonly responsible for.
**Boils** and **carbuncles** (clusters of boils) **Cellulitis** **Infected eczema** **Impetigo** **SSST**
30
What drugs can be used instead of fluxcloxacillin to treat MRSA?
**Doxycycline** **Co-trimoxazole** **Clindamycin** **Vancomycin**
31
Coagulase negative organisms like ***Staph. epidermidis*** are usually **(commensal / pathogenic)**.
**commensal**
32
When may *Staph. epidermidis* cause infection?
**Artificially implanted stuff** like pacemakers, joints, heart valves, catheters...
33
What kind of infection does *Staph. saprophyticus* tend to cause?
**UTIs** in women
34
***Streptococci*** are Gram positive organisms commonly found in **(clusters / chains)**.
**chains**
35
Name an enzyme produced by beta-haemolytic *Strep.* which damages tissues.
**Haemolysin**
36
What are some skin infections caused by *Strep. pyogenes* i.e Group A *Strep.*?
**Infected eczema** **Impetigo** **Cellulitis** **Erysipelas** (superficial dermatitis on face, upper & lower limbs) **NECROTISING FASCIITIS**
37
What **life-threatening** **condition** is caused by *Group A Strep**.*?
**Necrotising fasciitis**
38
What is the antibiotic of choice for treating *Staph. aureus* infections?
**Flucloxacillin**
39
What is the antibiotic of choice for treating *Strep. pyogenes* (Group A) infections?
**Penicillin / Flucloxacillin**
40
In addition to giving penicillin, what needs to be done for a patient with necrotising fasciititis?
**Immediate removal of affected tissue**
41
Although there is little to see on the skin itself, what is the main symptom of necrotising fasciitis? Why?
**Severe pain** **Infection is spreading along the fascia, destroying all the tissue**
42
A leg ulcer tends to be a ___ problem only.
**vascular** i.e you don't need to give antibiotics
43
What investigation should be carried out if a leg ulcer looks infected?
**Swabs**
44
What drug should you add to fluclox/penicillin if you suspect that there are **anaerobes** in a diabetic foot ulcer?
**Metronidazole**
45
What kind of infection is **ringworm**?
**Fungal infection**
46
What does **tinea** mean?
**Ringworm**
47
Where is **tinea capitis** found?
**Scalp**
48
Where is **tinea barbae** found?
**Beard**
49
Where is **tinea corporis** found?
**Body**
50
Where is **tinea manuum** found?
**Hands**
51
Where is **tinea unguium** found?
**Nails**
52
Where is **tinea cruris** found?
**Groin**
53
Where is **tinea pedis** found? What is this infection also known as?
**Feet** **Athlete's foot**
54
What is the fungus responsible for 70% of ringworm infections?
***Trichophyton rubrum***
55
How is ringworm infection diagnosed?
**By examination +/- Wood's lamp** **Nail/hair/skin shavings sent for microscopy and culture**
56
What is used to treat small fungal infections on the hair or nails?
**Clotrimazole cream** (Candesan) **Amorolfine nail paint**
57
What is used to treat fungal scalp infections?
**Terbinafine orally** **Itraconazole orally**
58
Where do *Candida.* infections tend to be seen?
**Warm, moist areas** - breasts, groin areas, skin folds, nappy area
59
How is *Candida.* infection diagnosed?
**Swabs \> Culture**
60
What is given to treat *Candida* infections?
**Clotrimazole cream** (Cantesan) Oral fluconazole i.e antifungals
61
What is **scabies**?
**Itchy rash on fingers, wrists and genitals**
62
What is the **chronic, crusty form** of scabies called?
**Norwegian scabies**
63
What is the organism causing scabies?
***Sarcoptes scabiei***
64
What are some treatment options for scabies?
**Malathion lotion** **Benzyl benzoate**
65
What else is treated with malathion lotion?
**Lice**

Dermatology Week 2 2017/18 (8 decks)

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