Typing Methods

Question 1

Agglutination test

Answer 1

Mix drop of saline with sample and add antiserum
Iff agglutination occurs then antigen is present in sample (+ve)

Question 2

Polymerase Chain Reaction (PCR)

Answer 2

Selectively amplifies a small targeted area of genome (gene/locus)

Question 3

Pros of PCR

Answer 3

Specific
Relatively quick

Question 4

Cons of PCR

Answer 4

Does not distinguish between live/dead cells
Only samples small part of genome
* May falsely link isolates which have differences elsewhere in genome

Question 5

Phage typing

Answer 5

Sensitivity of bacterium to panel of bacteriophages

Question 6

Pros of phage typing

Answer 6

Specific
No specialist equipment needed

Question 7

Cons of phage typing

Answer 7

Phage sensitivity might change
Needs skilled person to interpret
Labour intensive

Question 8

Pulse field electrophoresis

Answer 8

Extracts and cuts whole genome with enzymes
Restriction fragments are run on a pulsed field gel

Question 9

Pros of pulse field electrophoresis

Answer 9

Samples whole genome
Cane be standardised

Question 10

Cons of pulse field electrophoresis

Answer 10

Expensive equipment/software needed
Labour intensive

Question 11

Serotyping

Answer 11

Bacteria mixed with specific antisera
Antibodies agglutinate cells

Question 12

Pros of serotyping

Answer 12

Specific
Easy

Question 13

Cons of serotyping

Answer 13

Expensive if lots of serotypes involved
Can’t differentiate strains

Question 14

IMViC

Answer 14

Indole, Methyl red, Vogues-Proskauer, Citrate
* Biochem tests to differentiate coliform

Question 15

Pros of IMViC

Answer 15

Easy
Robust

Question 16

Cons of IMViC

Answer 16

Labour intensive
Doesn’t distinguish strains

Question 17

Gene sequencing

Answer 17

Targeted gene (PCR) or whole genome
+ Can distinguish strains
- Expensive equipment

Question 18

Transport requirements for samples

Answer 18

In transport medium
4 degrees
Aseptic technique
<48h