Culturing

Question 1

examples of non selective media?

Answer 1

• nutrient agar
• horse blood agar
• chocolate agar

Question 2

nutrient agar?

Answer 2

-agar
-peptone
-small amount of yeast extract.
Supports growth of most fastidious bacteria

Question 3

Horse blood agar?

Answer 3

-NA + 5% sterile horse blood

haemolysis

Question 4

haemolysis in horse blood agar plate?

Answer 4

• Alpha = partial haemolysis (greenish)
• Beta = complete haemolysis (clear)
• Gamma = no haemolysis (unchanged)

Question 5

chocolate agar?

Answer 5

• HBA which has been heated to disrupt the red cells, thus releasing extra growth factors including haemin and NAD.
• incubated at 10% CO2

Question 6

What are exmaples of things that need Chocolate agar?

Answer 6

Neisseria spp and Haemophilus spp.

Question 7

what are commonly used selective media?

Answer 7

• macConkey agar
• mannotil salt agar
• Xylose lysin desoxycholate

Question 8

macconkey agar?

Answer 8

• 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)

Question 9

mannitol salt agar?

Answer 9

-high salt content inhibits growth of virtually all bacteria except staphylococci. S. aureus ferments mannitol - indicator colour changes to yellow.

Question 10

Xylose desoxycholate agar?

Answer 10

• 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.

Question 11

disadvantage of light microscopy?

Answer 11

not suitable for viruses.

Question 12

disadvantage of molecular diagnosis?

Answer 12

• have to know specific strain before PCR.

- cannot tell if organism alive or dead.

Question 13

Typical and atypical penumonia?

Answer 13

ANSWER.

Question 14

what cells do lungs have?

Answer 14

simple, squamous, epithelium - allows passage of gas.