Lab 29: Agglutination

Question 1

what is the purpose of rapid tests?

Answer 1

to quickly identify unknown organisms or agents such as Staphylococcus aureus

Question 2

what happens if Staphylococcus aureus is displaced? what can it cause?

Answer 2

it can cause infections of:
-Hair follicles: boils
-Skin: impetigo
-Subcutaneous connective tissue: cellulitis
-Heart: endocarditis
-Bone: osteomyelitis
-Lungs: pneumonia
-Blood: bacteremia
-Causes toxic shock syndrome, necrotizing fasciitis, SFI due to toxins

Question 3

what is the S. aureus rapid test? Is it a direct or passive immunoassay?

Answer 3

It is a passive agglutination test - testing for the Ag.
So it is an immunoassay that is passive, looking for the Ag.

Question 4

what does the passive agglutination test for S. aureus contain? what are the steps?

Answer 4

1. Use latex beads coated with anti-Staph Ab’s
2. Add the Staph Ag
3. Agglutination or clumping of the beads = a positive test

Question 5

what is a positive test result for S. aureus rapid test?

Answer 5

Agglutination or clumping of the latex beads

Question 6

what does the virulence factor, Clumping factor A, do for S. aureus?

Answer 6

ClfA, Clumping Factor A, binds to fibrinogen.
This allows the crosslinking of bacterial cells to form a big clump that is hard to phagocytose.
This also helps in attachment of bacteria to our tissues.

Question 7

what does the virulence factor, Protein A, do for S. aureus?

Answer 7

SpA, Protein A, binds to the Anitbodie’s FC regions. This prevents opsonization.

Question 8

what type of S. aureus rapid test did we perform in lab?

Answer 8

We performed the StaphTex Blue test

Question 9

what is the StaphTex blue test?

Answer 9

When we use beads coated with both:
-Fibrinogen proteins (ClfA)
AND
-Protein A

Question 10

what two virulence factors are utilized in S. aureus’s StaphTex Blue Test?

Answer 10

Clumping Factor A (ClfA)
and
Protein A (SpA)

Question 11

what does the Clumping Factor A do within the StaphTex Blue Test?

Answer 11

The Fibrinogen proteins and coated with beads and they bind to the Clumping factor A

Question 12

what does Protein A do within the StaphTex Blue Test?

Answer 12

The Fc region of Antibodies are coated with beads and bind to the S. aureus protein A

Question 13

what does a positive StaphTex Blue Test look like?

Answer 13

Clotting and agglutination

Question 14

what other bacteria can also cause clumping by binding to Antibotides’ Fc regions?

Answer 14

Streptococcus spp. - Catalase (-)
Enterobacteriacae - Gram (-)
S. aureus - Catalase (+) and Gram (+)