Microbiology

Question 1

ways the skin protects itself from infection

Answer 1

• producing sebum prevents bacterial growth
• dry skin desiccates organisms
• competitive bacterial flora (staph epidermidis, Corynebacterium and Propionibacterium)

Question 2

five virulence factors

Answer 2

adhesin
invasin
impedin
aggressin
modulin

Question 3

define an adhesin

Answer 3

enables binding of the organism to the host tissue

Question 4

define an invasin

Answer 4

enables the organism to invade host cell/tissue

Question 5

define impedin

Answer 5

enables the organism to avoid host defence mechanisms

Question 6

define aggressin

Answer 6

causes damage to host directly

Question 7

define modulin

Answer 7

induces damage to host indirectly

Question 8

staph aureus virulence factors

Answer 8

• fibrinogen binding protein
• leucocidin
• enterotoxin (food poisoning)
• TSST-1
• coagulase
• PVL

Question 9

choice treatment for staph aureus

Answer 9

flucloxacillin

Question 10

When is flucloxacillin not used for staph aureus

Answer 10

MRSA

Question 11

describe TSST-1

Answer 11

superantigen that is associated with scalded skin syndrome and toxic shock syndrome (causes massive release of cytokines)

Question 12

describe PVL strain

Answer 12

Panton-Valentine-Leukocidin is a leucocyte killing strain that is associated with furunculosis, necrotising pneumonia and fasciitis

Question 13

strep pyogenes (group A) haemolysis

Answer 13

beta haemolysis

Question 14

how is group A strep classified?

Answer 14

Lancefield system which serotypes for carbohydrate and M1 in the cell wall

Question 15

three skin infections caused by strep A

Answer 15

1. impetigo
2. cellulitis (erysipelas)
3. necrotising fasciitis

Question 16

define cellulitis

Answer 16

deeper infection of the dermis not associated with necrosis

Question 17

define necrotising fasciitis (group A)

Answer 17

destroys connective tissue with streptolysin (SLS)

Question 18

virulence factors of strep pyogenes

Answer 18

superantigen
haemolysins SLO and SLS (aggressin)
M protein (adhesin)

Question 19

two fungal infections of the skin

Answer 19

1. dermatophyte (ringworm)

2. candida

Question 20

how does dermatophyte cause skin infections

Answer 20

fungus enters soggy skin affecting keratinised tissues

Question 21

causative organisms of dermatophyte

Answer 21

trichophyton rubrum
trichophyton mentagraphytes
microsporum canis

Question 22

diagnosis of dermatophyte

Answer 22

clinical appearance (ringworm)
woods light
skin scraping and/or hair/nail clippings

Question 23

management of dermatophyte

Answer 23

clotrimazole
topical nail paint (amorolfine)
scalp- terbinafine and itraconzole

Question 24

where does candida infect?

Answer 24

warm and moist areas

Question 25

diagnosis of candida

Answer 25

swab for culture

Question 26

candida management

Answer 26

clotrimazole

fluconazole

Question 27

two parasitic skin infections

Answer 27

1. scabies

2. lice

Question 28

scabies presentation

Answer 28

presents as an itchy rash (can have an incubation period of 6 weeks)

Question 29

scabies management

Answer 29

malathion lotion and benzyl benzoate

Question 30

presentation of lice

Answer 30

intense itch

Question 31

management of lice

Answer 31

malathion

Question 32

infection controls

Answer 32

isolation for strep A, MRSA and scabies