Skin and wound infections

Question 1

What features of the skin make it an effective barrier to infection?

Answer 1

Epidermis, Dermis and hypodermis

Question 2

What are some colonization hotspots for S.aureus and MRSA?

Answer 2

Nose, Intestines, Vagina and Skin ( armpits, chest/abdomen and pelvic area)

Question 3

What are some examples of normal microbiota (commensal organisms – bacteria)?

Answer 3

Fungi
Gram negative
Gram positive rods
Coagulase neg + positive staphylococci

Question 4

What is the correct order of
Eikenella corrodens
Cardiobacterium hominis
Hameophilus spp
Kingella spp
Aggregatibacter actinomycetemcomitans

Answer 4

HACEK

Question 5

Give 3 examples of skin infection

Answer 5

Cellulitis, Folliculitis and Abscess (pus accumulation in tissues)

Question 6

Give an example of a skin infection and its symptoms.

Answer 6

• Folliculitis
  – Hair follicle infection & inflammation

Question 7

What happens in a boil?

Answer 7

Coagulase leads
to fibrin formation,
and fibrin walls
off infection.

Leukocidin and
enzymes lead to
pus formation

Escaping pus

Question 8

What are superantigens associated with other than TSST? ()

Answer 8

Superantigens NOT only associated with TSS
Often implicated in food poisoning cases - enterotoxins produced by strains of s.aureus

Question 9

what is TSST?

Answer 9

Toxic shock syndrome toxin - is a superantigen and these are bacterial toxins

Question 10

What are the three gram-positive arrangements?

Answer 10

Tetrad, Chain and Grape-like clusters
Remember as TCG

Question 11

What are the coagulase test results for Staphylococcus aureus and Staphylococcus epidermidis what does it help identify?

Answer 11

The coagulase test helps identify staphylococcus aureus.
* Staphylococcus aureus - POSITIVE

• Staphylococcus epidermidis - NEGATIVE

Question 12

What are the key features of Staphylococcus epidermidis?

Answer 12

– Coagulase negative
– Non-pigmented
– Skin commensal

Question 13

What are the key features of Staphylococcus aureus?

Answer 13

Coagulase positive
– Yellow pigmentation
– Carriage in nasal passage
– Pathogenic

Question 14

Is Staphylococcus aureus gram-negative or gram-positive?

Answer 14

Gram positive

Question 15

S. aureus is halotolerant: what does this mean?

Answer 15

• It will grow in the presence of salt
• Property used in selective media

Question 16

Give 3 examples of wound infections.

Answer 16

Bites
Burn infections
Bowel surgery

Question 17

What infection causes tissue necrosis and gas production and what else does it cause?

Answer 17

Gangrene, also causes gas production

Question 18

Name the 4 Lancefield groupings

Answer 18

• Rebecca Lancefield
• Cell wall carbohydrates
• Serologic grouping (traditional)
• Agglutination assays

Question 19

What does SSTI stand for

Answer 19

Skin and soft tissue infection

Question 20

What does SSI?

Answer 20

Surgical site infection

Question 21

What results do Commercial latex agglutination assays show (kits available involving slide coagulase of S.
aureus)?

Answer 21

S. aureus - positive (clumps)
Staphylococci - negative (don’t clump)

Question 22

What are some virulence factors found in S. aureus (for cell surface proteins)?

Answer 22

Protein A
Clumping factor (binds to fibrinogen)
Fibronectin - binding protein

Question 23

What are some virulence factors found in S. aureus (Exotoxins)?

Answer 23

a-lysin, b-lysin, g-lysin, d-lysin
Toxic shock syndrome toxin
Coagulase
Lipase