Lecture 6 - Gastrointestinal Disease 2 Flashcards
What can light microscopy show us when investigating GIT disease?
Cysts
‘Pus’ cells –> inflammation
Parasites
What can electron microscopy show us when investigating GIT disease?
Viruses
Describe the process of Latex agglutination / EIA / ELISA?
- Known Ab place on bottom
- Unbound sites blocked
- Antigen added from sample
- Known Ab with conjugated enzyme added
- Substrate for enzyme added
- Colour is read
What are routine media?
DCA
MAC
What are specialised media?
CAMP
BCSA
BP
CIN
What are enrichment media?
Selenite broth
How would we first identify significant isolates?
Biochemical tests
How would we confirm the pathogen?
Serological tests
How do we compare strains?
Phage typing
PFGE
How do we look for specific virulence determinants?
PCR
Gel electrophoresis
What are the features of Enterobacteriaceae?
GNR
Ox. Negative
Fermenters
What are the features of Vibrio (Vibrionaceae)?
GN (curved) R
Ox. positive
Fermenters
Motile
What are the features of Campylobacter (Vibrionaceae)?
GN (curved) R
Oc. positive
LNF
What does MAC allow to grow?
E. coli
Salmonella, Shigella
How do we differentiate between E. coli, Shigella and Salmonella on MAC?
Lactose fermenters –> pink (E. coli)
LNF –> Yellow / colourless (Salmonella, Shigella)
What does DCA allow to grow?
Similar to MAC
Salmonella: black dot
What do we do after culture on routine media?
Look for suspicious colonies:
LNF: Shigella, Salmonella, Yersinia
These are not normal flora of the gut
What does Selenite broth allow to grow?
Salmonella spp. –> brick red
What does BP select for?
Staphylococcus aureus –> black with zone of clearing
What does BCSA select for?
Bacillus cereus –> blue + white precipitate
What does CAMP select for?
Campylobacter
Describe how an agglutination reaction works
Bacteria + antibody –> visibly agglutinates
What is phage typing used for?
To determine the source: same phage types –> same source?
Describe the process of phage typing
- Lawn culture of bacteria applied to plate
- Panel of phages dotted onto a grid
- Incubation of plate
- Pattern of areas of lysis read
- Phage type assigned
What bacteria is phage typing used for?
Salmonella
S. aureus
What is PCR used for?
Determining the presence of specific virulence determinants
eg. LT, ST and bfp