Lecture 10: Diagnosing Infection

Question 1

What are the three main steps in diagnosing an infection?

Answer 1

1. Demonstrate the organism.
2. Isolate the micro-organism.
3. Demonstrate a serological response.

Question 2

What methods can we use to demonstrate an organism?

Answer 2

Microscopy, immunofluorescence, immunohistochemistry, capture assay, nucleic acid detection, MALDI-TOF.

Question 3

What is Immunohistochemistry?

Answer 3

Linking a primary antibody with known specificity to an antigen. If it binds, then colour changes, and we know what the antigen is.

Question 4

What is capture assay?

Answer 4

Wash an antibiotic over a few different antigens (known), if it sticks, then colour change.

Question 5

What are the two ways nucleic acid detection can be done?

Answer 5

Hybridisation: Synthesising a probe with a label and mixing it to allow it reanneal. If it reanneals, then the target DNA has been found as the label will light up.

PCR: Target DNA melted to give single strands. Primer then binds to homologous sequence and DNA polymerase synthesises two separate new strands.

Question 6

True or false? All organisms have the same primer region.

Answer 6

False. But most do.

Question 7

What is immunoblot (western blot) used for in diagnosing an infection?

Answer 7

Demonstrating a serological response.