Enterobacterales Flashcards
1
Q
Describe Enterobacterales
A
- widely studied family of organisms
- over 50 genera
- over 170 species
- causative agents of diseases such as meningitis, typhoid, UTI, septicaemia
2
Q
What are the virulent factors of Enterobacterales?
A
- outer membrane can be either core polysaccharide, O polysaccharide or lipid A
- capsule
- fimbriae
- exotoxins
- type III secretion system
2
Q
What do enterobacterale account for?
A
- most Gram negative healthcare associated infections
3
Q
How can the pathogenic members of the Enterobacterales be split into groups?
A
- coliforms -> ferments lactose
- coliform opportunists -> does not ferment lactose
- true pathogens
4
Q
What are some problems with identifying Enterobacterales ?
A
- similar in microscopic appearance & staining properties
- many different species can cause similar symptoms
- identification important for current therapy
5
Q
What is the typical culture media used for enterobacterales ?
A
-primary isolation media
- blood, MacConkey, XLD, CLED
- most species grow well at 37
6
Q
Describe XLD
A
- Xylose Lysine Desoxycholate
- isolation of salmonellae & shigellae
- selective & differential
- Xylose fermentation
7
Q
Describe CLED
A
- Cysteine Lactose Electrolyte Deficient
- differential
- electrolyte deficient
- andrade indicator
8
Q
Describe the Oxidase test
A
- scrape some fresh growth from culture plate with disposable loop & rub on filter paper
- examine for blue colour within 10s
- positive = development of blue cloud indicates oxidase production
- negative = no blue colour
9
Q
What is the positive result of the catalase test ?
A
- vigorous bubbling indicates the presence of catalase
10
Q
What is the negative result of the catalase test ?
A
= no bubbling
