Microbiology

Question 1

Define ‘virulence’

Answer 1

The ability of an organism to cause disease within a host

Question 2

Name 5 virulence factors

Answer 2

Adhesin
Impedin
Invasin
Aggressin
Modulin

Question 3

What are adhesins?

Answer 3

Bacterial cell surface components that help the organism stick/adhere to host tissue

Question 4

What are invasins?

Answer 4

Enable organisms to invade host tissue

Question 5

What are impedins?

Answer 5

Help the organism avoid the defence/immune response in host tissue

Question 6

What are aggressins?

Answer 6

Cause direct damage to host tissue + immune cells, affecting the host’s ability to cope with disease in the future

Question 7

What are modulins?

Answer 7

Cause indirect damage to the host by turning the immune system in on itself (host’s immune system causes damage to host tissue)

Question 8

The nasal strain of Staph. aureus can protect the mucosa. True/False?

Answer 8

True

Question 9

Staph. epidermidis can occupy up to 100% of our skin. True/False?

Answer 9

True

Question 10

Where is the most common entry of Staph. aureus into the body?

Answer 10

Nasal entry

Question 11

Name the 3 particularly important virulence factors of Staph. aureus disease

Answer 11

Fibrinogen-binding protein (adhesin)
Leukocidin (kills leukocytes)
TSST-1 (toxin)

Question 12

Every strain of Staph. aureus carries every virulence factor. True/False?

Answer 12

False

Question 13

Which 2 severe skin diseases is leukocidin associated with?

Answer 13

Necrotising fasciitis

Recurrent furunculosis

Question 14

Leukocidin is more virulent in hospital-acquired MRSA than community-acquired. True/False?

Answer 14

False

Question 15

Give an example of a superantigen released by MRSA

Answer 15

TSST-1 (toxic shock)

Question 16

How exactly do superantigens avoid specific T-cell activation?

Answer 16

Bind to MHC II complex on the outside, i.e. not the conventional binding groove

Question 17

Name 3 skin infections caused by Strep. pyogenes

Answer 17

Impetigo
Cellulitis
Necrotising fasciitis

Question 18

How does the Lancefield system classify different subtypes of Step. pyogenes?

Answer 18

M-protein

M1 and M3 are predominant; M3 and M18 cause severe, invasive disease

Question 19

Which 2 virulence factors are particularly important as adhesins for Strep. pyogenes disease?

Answer 19

Hyaluronic acid (sticky capsule)
CD44 +ve keratinocytes

Question 20

The bigger the capsule, the less virulent an organism is. True/False?

Answer 20

False

Question 21

Where does impetigo usually affect?

Answer 21

Face

Question 22

Where in the body is Strep. pyogenes normally found?

Answer 22

Throat

Question 23

Which strain of Staph aureus commonly produces abscesses and boils, usually affecting numerous family members at once?

Answer 23

PVL (panton valentine leukocidin)

Question 24

Which group of Strep causes throat and severe skin infections?

Answer 24

Group A

Question 25

Which bacteria cause impetigo?

Answer 25

Staph aureus | Group A Strep

Question 26

Which bacteria tends to cause nectrotising fasciitis?

Answer 26

Group A Strep (pyogenes)

Question 27

What is the treatment of choice for Staph aureus?

Answer 27

Flucloxacillin

Question 28

What is the treatment of choice for Strep pyogenes?

Answer 28

Penicillin

Question 29

What is necrotising fasciitis?

Answer 29

Bacterial infection spreading under the skin into fascia

Question 30

What is the nickname of necrotising fasciitis?

Answer 30

Flesh-eating bacterial disease

Question 31

Type I necrotising fasciitis is caused by Group A Strep. True/False?

Answer 31

False Type I = mixed anaerobes and coliforms Type II = group A Strep

Question 32

What is the most common skin fungal infection caused by?

Answer 32

Ringworm (Tinea)

Question 33

Tinea pedis is another name for what?

Answer 33

Athlete's foot

Question 34

How is dermatophyte infection caused?

Answer 34

Fungus enters abraded skin and infects keratinised tissue, provoking inflammation and outward lesioning

Question 35

Which organism is the most common cause of dermatophyte infection?

Answer 35

Trichophyton rubrum

Question 36

How are small areas of dermatophyte infection treated?

Answer 36

Clotrimazole cream | Nail paint

Question 37

How are dermatophyte scalp infections treated?

Answer 37

Terbinafine oral | Itraconzole oral

Question 38

Which parasite causes scabies?

Answer 38

Sarcoptes scabiei

Question 39

Incubation of the scabies parasites takes up to how long?

Answer 39

6 weeks

Question 40

How is scabies treated?

Answer 40

``` Malathion lotion overnight Benzyl benzoate (not in children) ```

Question 41

Chickenpox and shingles are due to which virus?

Answer 41

Varicella zoster

Question 42

Where does varicella zoster become dormant following chickenpox?

Answer 42

Dorsal root ganglia of spine

Question 43

Chickenpox can cause pneumonitis and encephalitis. True/False?

Answer 43

True

Question 44

What is Ramsay-Hunt syndrome?

Answer 44

Reactivation of VZV in CN VII | Causes vesicles and pain in auditory canal and throat

Question 45

What does herpes simplex virus cause around the mouth?

Answer 45

Primary gingivostomatitis | Extensive ulceration

Question 46

What is the treatment of choice for varicella zoster and herpes simplex virus?

Answer 46

Aciclovir

Question 47

Which virus tends to cause warts?

Answer 47

Human papilloma virus

Question 48

Which treatment is effective for warts?

Answer 48

Salicylic acid

Question 49

Which bacterium causes syphilis?

Answer 49

Treponema pallidum

Question 50

How is syphilis treated?

Answer 50

Penicillin injections