Lecture 6 - Gastrointestinal Disease 2

Question 1

What can light microscopy show us when investigating GIT disease?

Answer 1

Cysts
‘Pus’ cells –> inflammation
Parasites

Question 2

What can electron microscopy show us when investigating GIT disease?

Answer 2

Viruses

Question 3

Describe the process of Latex agglutination / EIA / ELISA?

Answer 3

1. Known Ab place on bottom
2. Unbound sites blocked
3. Antigen added from sample
4. Known Ab with conjugated enzyme added
5. Substrate for enzyme added
6. Colour is read

Question 4

What are routine media?

Answer 4

DCA

MAC

Question 5

What are specialised media?

Answer 5

CAMP
BCSA
BP
CIN

Question 6

What are enrichment media?

Answer 6

Selenite broth

Question 7

How would we first identify significant isolates?

Answer 7

Biochemical tests

Question 8

How would we confirm the pathogen?

Answer 8

Serological tests

Question 9

How do we compare strains?

Answer 9

Phage typing

PFGE

Question 10

How do we look for specific virulence determinants?

Answer 10

PCR

Gel electrophoresis

Question 11

What are the features of Enterobacteriaceae?

Answer 11

GNR
Ox. Negative
Fermenters

Question 12

What are the features of Vibrio (Vibrionaceae)?

Answer 12

GN (curved) R
Ox. positive
Fermenters
Motile

Question 13

What are the features of Campylobacter (Vibrionaceae)?

Answer 13

GN (curved) R
Oc. positive
LNF

Question 14

What does MAC allow to grow?

Answer 14

E. coli

Salmonella, Shigella

Question 15

How do we differentiate between E. coli, Shigella and Salmonella on MAC?

Answer 15

Lactose fermenters –> pink (E. coli)

LNF –> Yellow / colourless (Salmonella, Shigella)

Question 16

What does DCA allow to grow?

Answer 16

Similar to MAC

Salmonella: black dot

Question 17

What do we do after culture on routine media?

Answer 17

Look for suspicious colonies:
LNF: Shigella, Salmonella, Yersinia

These are not normal flora of the gut

Question 18

What does Selenite broth allow to grow?

Answer 18

Salmonella spp. –> brick red

Question 19

What does BP select for?

Answer 19

Staphylococcus aureus –> black with zone of clearing

Question 20

What does BCSA select for?

Answer 20

Bacillus cereus –> blue + white precipitate

Question 21

What does CAMP select for?

Answer 21

Campylobacter

Question 22

Describe how an agglutination reaction works

Answer 22

Bacteria + antibody –> visibly agglutinates

Question 23

What is phage typing used for?

Answer 23

To determine the source: same phage types –> same source?

Question 24

Describe the process of phage typing

Answer 24

1. Lawn culture of bacteria applied to plate
2. Panel of phages dotted onto a grid
3. Incubation of plate
4. Pattern of areas of lysis read
5. Phage type assigned

Question 25

What bacteria is phage typing used for?

Answer 25

Salmonella | S. aureus

Question 26

What is PCR used for?

Answer 26

Determining the presence of specific virulence determinants eg. LT, ST and bfp