Culturing Flashcards
examples of non selective media?
- nutrient agar
- horse blood agar
- chocolate agar
nutrient agar?
-agar
-peptone
-small amount of yeast extract.
Supports growth of most fastidious bacteria
Horse blood agar?
-NA + 5% sterile horse blood
haemolysis
haemolysis in horse blood agar plate?
- Alpha = partial haemolysis (greenish)
- Beta = complete haemolysis (clear)
- Gamma = no haemolysis (unchanged)
chocolate agar?
- HBA which has been heated to disrupt the red cells, thus releasing extra growth factors including haemin and NAD.
- incubated at 10% CO2
What are exmaples of things that need Chocolate agar?
Neisseria spp and Haemophilus spp.
what are commonly used selective media?
- macConkey agar
- mannotil salt agar
- Xylose lysin desoxycholate
macconkey agar?
- selective agent - presence of bile salts (G- and GIT)
- contains lactose, if used by bacteria, the bacteria produce lactic acid (pH drops and turns red) while nonlactating bacteria turn yellow (due to breakdown of amino acids)
mannitol salt agar?
-high salt content inhibits growth of virtually all bacteria except staphylococci. S. aureus ferments mannitol - indicator colour changes to yellow.
Xylose desoxycholate agar?
- used to differentiate between enteric bacteria
- shigella = appears red (cannot metabolise the 3 carbs on the agar)
- salmonella = can ferment xylose, however decrease in pH and production of H2S, forming red circles with a central black spot
- generally, bacteria that can ferment any of the carbs appear yellow.
disadvantage of light microscopy?
not suitable for viruses.
disadvantage of molecular diagnosis?
- have to know specific strain before PCR.
- cannot tell if organism alive or dead.
Typical and atypical penumonia?
ANSWER.
what cells do lungs have?
simple, squamous, epithelium - allows passage of gas.
