Bacterial Virulence Flashcards Preview

RB Y2 Dermatology > Bacterial Virulence > Flashcards

Flashcards in Bacterial Virulence Deck (63)
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1
Q

define pathogenicity and virulence

A

pathogenicity - ability of organism to cause disease

virulence - degree of pathology (harm) caused by organism

2
Q

what are virulence factors

A

characteristics that enhance a bacteriums pathogenicity

3
Q

impendin

A

avoid host defence mechanisms

4
Q

agressin

A

cause damage to host directly

5
Q

modulin

A

induce damage to host indirectly

6
Q

what are superantigen exotoxins

A

have an affinity for the T cell MHC class II antigen complex, stimulate enhanced t cell response

7
Q

what is TSST-1 and what does it cause

A

superantigen TSS

8
Q

what does PVL do

A

make strains more virulent , specific toxicity for WBC

9
Q

what can PVL cause

A

severe skin infection eg necrotising fasciitis, pneumonia and sepsis

people are unusually sick

10
Q

what is PVL produced by

A

predominantly CA MRSA

11
Q

what are the treatment options for MRSA

A

include Doxycycline, Co- trimoxazole, Clindamycin, Vancomycin (not Flucloxacillin).

12
Q

what is necrotizing pneumonia

A

Pneumonia characterised by the development of the necrosis within infected lung tissue

13
Q

what can necrotizing pneumonia lead to

A

ARDS, deterioration in pulmonary function and multi organ failure

14
Q

what are the CF of TSS

A

high fever, rash, diffuse erythema followed by desquamation, vomiting and diarrhoea

15
Q

what does the rash resemble in TSS

A

sunburn

16
Q

what does the BP do in TSS

A

hypotension

17
Q

what causes TSS

A

S Pyogenes and S Aureus

18
Q

staphylococcal scalded skin syndrome characteristics

A

red blistering skin

19
Q

SSSS cause

A

S Aureus releases exfoliative toxin that causes blistering of the skin, ETA and ETB toxins target desmoglein 1

20
Q

where are desmogleins found

A

in keratinocytes

21
Q

where is S pyogenes normally found

A

pharynx

22
Q

what is S pyogenes classified using

A

lancefield classification - group A strep

23
Q

what is S pyogenes

A

lancefield: group A strep

group beta-haemolytic streptococci

24
Q

what does the lancefield classification use

A

based on carbohydrate composition of bacterial antigens found on cell wall

25
Q

what is special about S pyogenes structure

A

the capsule is made from hyaluronic acid which is identical to that found in human connective tissue - not recognised as foreign by body

26
Q

what does S pyogenes cell wall contain

A

M proteins - needs these to be infectious

27
Q

what is impetigo

A

highly contagious skin infection that causes sores and blisters - classical honey coloured crust

28
Q

what is impetigo caused by

A

S pyogenes is the classic cause, S aureus has been responisble for more recent cases

29
Q

what would you treat impetigo systemically

A

penicillin - effective against both aureus and pyogenes

30
Q

where about is the infection in impetigo

A

immediatly below surface (stratum corneum) typically face (children)

31
Q

what is cellulitis

A

Generalised term for a spreading infection in the dermis that isn’t associated with necrosis

Often affects the lower leg, causing an upward-spreading, hot erythema, and occasionally will blister. Patients often unwell with high temperature.

Caused by b-Haemolytic Streps and Staphs

32
Q

what do you treat cellulitis with

A

flucloxacillin

33
Q

erysipelas

A

a superficial form of cellulitis caused by S pyogenes

34
Q

what are the clinical features of erysipelas

A

sharply defined superficial infection

fever, rigours nausea

35
Q

what is Necrotising fasciitis

A

bacterial infection that spreads along fascial planes below skin surface causing rapid tissue destruction

36
Q

what causes type I Necrotising fasciitis

A

mixed anaerobes and coliforms, usually post abdo surgery

37
Q

what causes type II Necrotising fasciitis

A

group A strep infection

38
Q

what is a ringworm also called

A

tinea

39
Q

cruris

A

GROIN

40
Q

capitis

A

scalp

41
Q

manuum

A

hand

42
Q

unguium

A

nails

43
Q

tinia pedis

A

athletes foot

44
Q

what are dermatophytes

A

fungi that require keratin for growth

45
Q

describe the invasion of dermatophytes

A

fungus enteres the skin and hyphae spread through stratum corneum (dermatophytes require keratin for growth so only keratinised tissues are infected)

inc epidermal turnover = scaling

inflammatory response provoked

46
Q

what is the appearance of dermatophyte lesion

A

ring like

  • grows outwards and heals in the centre
47
Q

who is scalp ringworm (tinea capitis) most common in

A

children

48
Q

who is tinea pedis and cruruis most common in

A

men

49
Q

what is the most likely causative organism of ringworm

A

Trichophyton rubrum

Trichophyton mentagraphytes

Microsporum canis (cats and dogs to humans)

50
Q

what do you treat ringworm with

A

clotrimazole cream

topical nail paint - amorolfine

systemic involvement - oral terbinafine

51
Q

what can you treat scalp ringworm infections with

A

terbinafine orally and itraconazole orally

52
Q

what is candida

A

most common yeast infecion

53
Q

where is candida found

A

skin folds where area is warm and moist

54
Q

what is candida treated with

A

clotrimazole cream, oral flucanazole

55
Q

what is the parasitic infection scabies caused by

A

sarcoptes scabiei

56
Q

what is the chronic crusted form of scabies called

A

norwegian scabies

57
Q

what is the incubation period of scabies like

A

up to 6 weeks

58
Q

treatment of scabies

A

malathion lotion

benzyl benzoate in children

59
Q

scabies CF

A

intensely itchy rash affecting finger webs, wrists and genital area

60
Q

what is the treatment for lice

A

malathion

61
Q

what is vagabonds disease

A

pediculus corporos

62
Q

what colour do alpha haemolytic streptococci go

A

green (partial)

63
Q

what colour do beta haemolytic streptococci go

A

yellow (full)