Laboratory diagnosis of infection

Question 1

Specimens for analysis

Answer 1

Swabs, tissue and cfs

Question 2

C. diff identification

Answer 2

GDH and toxin detection tests

Question 3

Direct detection

Answer 3

Lateral flow and 96 well format

Quick but doesn’t identify antimicrobial susceptibility or the type

Question 4

Identification of nucleic acids

Answer 4

used in virology and for fastidious bacteria

Question 5

Non selective culture media

Answer 5

• Chocolate
• Blood
• Nutrient agar

Question 6

Indicator media

Answer 6

-Sugar fermenting
-MacConkey
CLED

Question 7

MacConkey agar

Answer 7

• Selects for enteric bacteria

- Bile salts select and lactose shows it ferments via colour change

Question 8

Staphylococcus aureus

Answer 8

Gram positive cocci

Clumps

Question 9

Streptococcus pyogenes

Answer 9

Gram positive cocci

Chains

Question 10

Beta haemolysis

Answer 10

Complete breakdown of RBCs

Question 11

Oxidase test

Answer 11

Shows pseudomonas as the last cytochrome in the chain is oxidase which is specific to pseudomonas

Question 12

MALTI-TOF

Answer 12

Mass spectrometry
Produces a spectrum of bacterial proteins which are compared to a database
Cheap and fast
Work if can be grown in culture

Question 13

Immunological tests

Answer 13

Look for antibodies such as in the four fold rise in titre

Can identify IFN-y released during TB infection