Bacterial Virulence

Question 1

define pathogenicity and virulence

Answer 1

pathogenicity - ability of organism to cause disease

virulence - degree of pathology (harm) caused by organism

Question 2

what are virulence factors

Answer 2

characteristics that enhance a bacteriums pathogenicity

Question 3

impendin

Answer 3

avoid host defence mechanisms

Question 4

agressin

Answer 4

cause damage to host directly

Question 5

modulin

Answer 5

induce damage to host indirectly

Question 6

what are superantigen exotoxins

Answer 6

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

Question 7

what is TSST-1 and what does it cause

Answer 7

superantigen TSS

Question 8

what does PVL do

Answer 8

make strains more virulent , specific toxicity for WBC

Question 9

what can PVL cause

Answer 9

severe skin infection eg necrotising fasciitis, pneumonia and sepsis

people are unusually sick

Question 10

what is PVL produced by

Answer 10

predominantly CA MRSA

Question 11

what are the treatment options for MRSA

Answer 11

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

Question 12

what is necrotizing pneumonia

Answer 12

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

Question 13

what can necrotizing pneumonia lead to

Answer 13

ARDS, deterioration in pulmonary function and multi organ failure

Question 14

what are the CF of TSS

Answer 14

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

Question 15

what does the rash resemble in TSS

Answer 15

sunburn

Question 16

what does the BP do in TSS

Answer 16

hypotension

Question 17

what causes TSS

Answer 17

S Pyogenes and S Aureus

Question 18

staphylococcal scalded skin syndrome characteristics

Answer 18

red blistering skin

Question 19

SSSS cause

Answer 19

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

Question 20

where are desmogleins found

Answer 20

in keratinocytes

Question 21

where is S pyogenes normally found

Answer 21

pharynx

Question 22

what is S pyogenes classified using

Answer 22

lancefield classification - group A strep

Question 23

what is S pyogenes

Answer 23

lancefield: group A strep

group beta-haemolytic streptococci

Question 24

what does the lancefield classification use

Answer 24

based on carbohydrate composition of bacterial antigens found on cell wall

Question 25

what is special about S pyogenes structure

Answer 25

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

Question 26

what does S pyogenes cell wall contain

Answer 26

M proteins - needs these to be infectious

Question 27

what is impetigo

Answer 27

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

Question 28

what is impetigo caused by

Answer 28

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

Question 29

what would you treat impetigo systemically

Answer 29

penicillin - effective against both aureus and pyogenes

Question 30

where about is the infection in impetigo

Answer 30

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

Question 31

what is cellulitis

Answer 31

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** ​

Question 32

what do you treat cellulitis with

Answer 32

flucloxacillin

Question 33

erysipelas

Answer 33

a superficial form of cellulitis caused by S pyogenes

Question 34

what are the clinical features of erysipelas

Answer 34

sharply defined superficial infection fever, rigours nausea

Question 35

what is Necrotising fasciitis

Answer 35

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

Question 36

what causes type I Necrotising fasciitis

Answer 36

mixed anaerobes and coliforms, usually post abdo surgery

Question 37

what causes type II Necrotising fasciitis

Answer 37

group A strep infection

Question 38

what is a ringworm also called

Answer 38

tinea

Question 39

cruris

Answer 39

GROIN

Question 40

capitis

Answer 40

scalp

Question 41

manuum

Answer 41

hand

Question 42

unguium

Answer 42

nails

Question 43

tinia pedis

Answer 43

athletes foot

Question 44

what are dermatophytes

Answer 44

fungi that require keratin for growth

Question 45

describe the invasion of dermatophytes

Answer 45

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

Question 46

what is the appearance of dermatophyte lesion

Answer 46

ring like - grows outwards and heals in the centre

Question 47

who is scalp ringworm (tinea capitis) most common in

Answer 47

children

Question 48

who is tinea pedis and cruruis most common in

Answer 48

men

Question 49

what is the most likely causative organism of ringworm

Answer 49

**Trichophyton** rubrum **Trichophyton** mentagraphytes **Microsporum** canis (cats and dogs to humans)

Question 50

what do you treat ringworm with

Answer 50

clotrimazole cream topical nail paint - amorolfine systemic involvement - oral terbinafine

Question 51

what can you treat scalp ringworm infections with

Answer 51

terbinafine orally and itraconazole orally

Question 52

what is candida

Answer 52

most common yeast infecion

Question 53

where is candida found

Answer 53

skin folds where area is warm and moist

Question 54

what is candida treated with

Answer 54

clotrimazole cream, oral flucanazole

Question 55

what is the parasitic infection scabies caused by

Answer 55

sarcoptes scabiei

Question 56

what is the chronic crusted form of scabies called

Answer 56

norwegian scabies

Question 57

what is the incubation period of scabies like

Answer 57

up to 6 weeks

Question 58

treatment of scabies

Answer 58

malathion lotion benzyl benzoate in children

Question 59

scabies CF

Answer 59

intensely itchy rash affecting finger webs, wrists and genital area

Question 60

what is the treatment for lice

Answer 60

malathion

Question 61

what is vagabonds disease

Answer 61

pediculus corporos

Question 62

what colour do alpha haemolytic streptococci go

Answer 62

green (partial)

Question 63

what colour do beta haemolytic streptococci go

Answer 63

yellow (full)