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Medicine Dermatology > Bacterial Virulence/Microbiology > Flashcards

Bacterial Virulence/Microbiology Flashcards

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Dermatology Board Prep flashcards
1
Q

Virulence factor

A

Specific component of pathogen that causes disease

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2
Q

Staphylococcus tends to cause infection through what?

A

Sebaceous glands and hair follicles

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3
Q

Streptococcus tends to cause infection through what?

A

Damage in the skin

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4
Q

Why is staph aureus an effective pathogen?

A

It has many different virulence factors

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5
Q

Skin infections caused by staph aureus

A 
Rash
Folliculitis
Abscess
Carbuncle
Impetigo
Scalded skin syndrome
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6
Q

Toxinoses caused by staph aureus

A

Toxic shock

Scalded skin syndrome

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7
Q

Where is staph epidermidis usually found in the human body?

A

Skin and mucous membranes, as well as intestinal tract

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8
Q

When does staph epidermidis usually cause infection?

A

Tends not to cause infection unless person is immunocompromised, but can be associated with foreign devices associated with hospitals, e.g. catheters, cannula etc.

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9
Q

2 common sites for staph aureus

A

Nasal passages and perineum

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10
Q

Patients high risk for MRSA

A

Elderly and immunocompromised
Intensive care patients
Burns patients
Surgical patients

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11
Q

Toxinoses

A

Discrete disease associated with a single protein component, a toxin or exotoxin

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12
Q

Scalded skin syndrome:

  • Which age group is it normally found in?
  • Where does it usually occur on the body?
  • True or false - it is self-limiting
A

It is normally found in neonates
It usually occurs on the face, axilla and groin
True - it is self-limiting

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13
Q

In scalded skin syndrome, which toxins target what?

A

ETA and ETB toxins target desmoglein-1

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14
Q

Why is skin continuously shed from the body in scalded skin syndrome?

A

The toxin interferes with keratin cross-bridges

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15
Q

True or false - TSST-1 which causes toxic shock syndrome has a slow progression

A

False - it has a rapid progression

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16
Q

Symptoms of toxic shock syndrome

A 
High fever
Vomiting
Diarrhoea
Sore throat
Muscle pain
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17
Q

Superantigen

A

Type of antigen that results in excessive activation of the immune system - activate 1 in 5 T cells rather than 1 in 10,000

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18
Q

Example of superantigen

A

TSST-1

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19
Q

Diagnostic criteria for toxic shock syndrome

A

Fever 39˚
Diffuse macular rash and desquamation (“sunburn”)
Hypotension
≥3 organ systems involved

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20
Q

How long can it take for toxic shock syndrome to cause death

A

Hours

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21
Q

Adhesins

A

Extracellular matrix molecules that are present on epithelial, endothelial surfaces and as component of clots

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22
Q

Types of adhesins

A

Fibrinogen binding
Fibronectin binding
Collagen binding

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23
Q

Panton-Valentine Leukocidin has specific toxicity for which type of cell?

A

Leukocytes

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24
Q

What is necrotising pneumonia?

A

Severe complication of quite mild infections due to destruction of immune cells

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25
Q

What can necrotising pneumonia cause?

A

Respiratory distress and deterioration in pulmonary function
Refractory hypoxaemia
Multi-organ failure
(all despite antibiotic therapy)

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26
Q

Which protein is key for evasion of host defences for staph aureus?

A

Protein A

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27
Q

How does protein A cause evasion of host defences?

A

Protein A binds antibodies the wrong way round and interferes with the marking of the cell for destruction

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28
Q

Which bacteria causes impetigo?

A

Group A streptococci

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29
Q

Entry point for impetigo

A

Small defect in skin

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30
Q

Which layer of the skin does impetigo tend to be limited to?

A

Stratum corneum

31
Q

Treatment for impetigo

A

Improve hygiene and prescribe topical antimicrobials

32
Q

Who tends to get impetigo?

A

Children and areas of poor hygiene

33
Q

True or false: impetigo is not very contagious

A

False - it is highly contagious and can spread through contact with discharge on face, and scratching due to irritation

34
Q

Which bacteria causes cellulitis?

A

Group A streptococci

35
Q

Which layer of the skin does cellulitis affect?

A

Dermis and subcutaneous fat

36
Q

Clinical features of cellulitis

A

Fever, rigors, nausea, redness, swelling

37
Q

Which bacteria causes type 1 and type 2 necrotising fasciitis?

A

Type 1 = clostridia spp.

Type 2 = S pyogenes and S aureus

38
Q

Diagnosis of skin infections

A

Often clinical
Swab of surface if lesion is broken
Pus or tissue if deeper lesion
Blood cultures if systemically unwell

39
Q

Colour of staph aureus and coagulase negative staph

A

Staph aureus = golden

Coagulase negative staph = white

40
Q

Bacteria that may be commensals

A

Staph epidermidis
Corynebacterium
Propionibacterium

41
Q

Antibiotic of choice for staph aureus

A

Flucloxacillin

42
Q

Types of staph aureus toxins that can cause severe illness

A

Staphylococcus scalded skin syndrome (SSSST)
Panton Valentine Leucocidin
Food poisoning (enterotoxin)

43
Q

Conditions that staph aureus causes

A 
Boils and carbuncles
Minor skin infections
Cellulitis
Infected eczema
Impetigo
44
Q

Skin and soft tissue options for MRSA treatment

A

Doxycycline oral
Co-trimoxazole
Clindamycin
Linezolid

45
Q

Side effects of clindamycin and linezolid

A

Clindamycin - can cause C.diff

Linezolid - associated with anaemia

46
Q

Bactericidal options for MRSA treatment

A

Vancomycin

Daptomycin

47
Q

Conditions caused by group A strep infection

A 
Infected eczema
Impetigo
Cellulitis
Erysipelas 
Necrotising fasciitis
48
Q

Treatment for strep pyogenes

A

Penicillin

49
Q

Treatment for necrotising fasciitis

A

Immediate surgical debridement and antibiotics

50
Q

When are swabs taken for leg ulcers?

A

Only if cellulitis or infection are present

51
Q

Fungal skin infections

A

Candidiasis
Tinea - ringworm, athletes foot
Pityriasis

52
Q

Dermatophytes

A

Fungi that require keratin for growth

53
Q

What type of skin do dermatophytes tend to enter?

A

Abraded/soggy skin

54
Q

Which gender is most commonly affected by dermatophytes?

A

Males

55
Q

Diagnosis of dermatophytes

A

Clinical appearance
Woods light
Skin scrapings (from scaly edge of lesion), nail clippings, hair

56
Q

Treatment for small areas of infected skin, nails by dermatophytes

A

Clotrimazole (most common)

Topical nail paint

57
Q

Where does candida cause infection?

A

In the skin folds where the area is warm and moist

58
Q

Diagnosis of candida

A

Swab for culture

59
Q

Treatment for candida

A

Clotrimazole cream, oral fluconazole

60
Q

What causes scabies?

A

Sarcoptes scabiei

61
Q

Crusted form of scabies

A

Norwegian scabies - highly infectious

62
Q

Incubation period of scabies

A

Up to 6 weeks

63
Q

Clinical features of scabies

A

Intense rash affecting finger webs, wrists and genital area

64
Q

Treatment for scabies

A

Malathion lotion

65
Q

Pediculis capitis

A

Head lice

66
Q

Pedicuis corposus

A

Body lice

67
Q

Patients with which infections require single room isolation?

A

Group A strep
MRSA
Scabies

68
Q

Erythematous exanthems which tend to start on face

A

Measles
Rubella
Erythema infectiousum

69
Q

Erythematous exanthems which tend to start on trunk

A

Roseola
Scarlet fever
Unilateral laterothoracic exanthem

70
Q

Papulo-vesicular exanthems

A

Chicken pox

Gianotti-crosti syndrome

71
Q

Exanthems of the extremities

A

Hand, foot and mouth disease

72
Q

Direct methods of diagnosing viruses

A 
Virus isolation (culture)
Genome detection (PCR)
Antigen detection
73
Q

Indirect methods of diagnosing viruses

A

Serology IgM

Serology IgG

Medicine Dermatology (19 decks)

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