Investigating Infections

Question 1

What is MacConkey Agar?

Answer 1

Agar that is DIFFERENTIAL and SELECTIVE:

Bile Salts - which kills anything that isn’t a pathogen

Lactose indicator :
- positive lactose fermenter - red colour : example: E.Coli

• negative lactose fermenter - yellow colour - example: shigella, salmonella, or proteus (commensal)

Incubated at 37 degrees celcius in Air

Generally used to identify - GI TRACT INFECTION

Question 2

What is an example of Selective Media?

Answer 2

Selective Media : Campy Blood Agar

Selective for campylobacter
42 degrees celcius
10% CO2 / 5% O2
Anaerobic jar - microaerophile

Question 3

What is an example of enriched and differential medium?

Answer 3

Blood Agar
enriched: provides the nutrients for bacteria to grow

Differential: ability to differentiate between alpha hemolysis and beta hemolysis

Alpha hemolysis: brown/green tinge around the bacteria colonies - example: strep pneumonia

Beta Hemolysis: complete lysis around the colonies : strep pyogenes

Question 4

What is chocolate agar?

Answer 4

Chocolate agar is enriched medium : COOKED BLOOD
- kills the RBC
used for fastidious organisms : Neisseira Meningitis, haemophilus influenzae

Question 5

What is bacteriemia ? How can you identify organisms?

Answer 5

Presence of bacteria in the blood - occurs as a result of infection - usually resolves due to immune system

pathologies: meningitis and invasive strep pneumonia

Blood Culture in TWO DIFFERENT TYPES OF BOTTLES - aerobic and anaerobic to look for ALL TYPES of pathogen.

Question 7

What is septicemia

Answer 7

Severe Systemic Infection - presence of bacteria in blood stream