Exercise 7
Cards (12)
- Some distinct characteristics of family Enterobacteriaceae:
- gram negative bacilli
- facultative anaerobes
- non-spore forming
- possess fimbriae and flagella
- pathogenic
- antibiotic resistance
- genetic plasticity
- Different toxins produced by Enterobacters
- hemolysin
- cytotoxins
- endotoxins
- enterotoxins
- siderophores
- extracellular enzymes
- antiphagocytic capsule
- Citrate utilization
- to differentiate GNB of Enterobacteriaceae
- also called Simmon's citrate test
- Simmon's citrate agar - contains citrate as main source of energy in the citrate utilization
- Citrase - breaks down citrate into oxoloacetate and acetate, where oxoloacetate is further broken down to form pyruvate and carbon dioxide
- Positive citrate test - shift in pH level and change in color
- Methyl red test
- detects the production of sufficient acid during fermentation of glucose
- pH of an old culture is sustained below a value of about 4.5
- In Enterobacters, glucose is converted to pyruvic acid and further metabolized to produce stable acid (lactic acid, acetic acid, formic acid)
- Positive MR test - the color of methyl red changes from yellow to red
- Voges - proskauer test
- used to determine if an organism produces acetylmethyl carbinol from glucose fermentation
- if present, it is converted into diacetyl in the presence of alpha napthol
- The diacetyl and quanidine-containing compounds are then condensed to from a pinking red polymer.
- K - Alkaline, redA - Acidic, yellow