Microbiology A4 - Principles of Investigation

Question 1

Specimen Culture

Why is it done?

Answer 1

• Culture of the microbes in specimens amplifies the quantity to allow reliable detection, identification and sensitivity testing.

Question 2

Serology

How does serology identify pathogens?

Answer 2

Either through the immune response they raise, usually depending on rising or falling levels of antibodies in serial specimens or through specific antigen detection
- For example, CSF can be examined for bacterial capsular antigens which would indicate N. meningitides.

Question 3

Molecular Techniques

Name a common ‘molecular technique’ and why it might be preferred over the use of culture media.
Name 2 examples of pathogens disposed to this method of detection.

Answer 3

• Use nucleic acid amplification technology
  Good for identification of organisms that grow slowly.
  For example M. tuberculosis and C. trachomatis.

Question 4

What specimen is taken to look for a urinary tract infection

Answer 4

MSU

Question 5

What specimen is taken to look for skin wounds

Answer 5

Wound swab

Question 6

What specimen is taken to look for Meningitis

Answer 6

CSF and blood

Question 7

What specimen is taken to look for nonspecific pyrexia

Answer 7

Blood for culture and serology

Question 8

What specimen is taken to look for pneumonia

Answer 8

Blood and sputum

Question 9

What is liquid culture medium good for?

Answer 9

Maximising growth

Question 10

What is solid culture medium good for?

Answer 10

Separating organism types

Question 11

How do you examine stool parasites

Answer 11

Direct light microscopy

Question 12

How do you examine CSF bacteria

Answer 12

Gram stain light microscopy

Question 13

How do you examine sputum for TB

Answer 13

ZN stain light microscopy

Question 14

How do you examine blood for malaria

Answer 14

Giemsa stain

Question 15

How do you examine sputum for RSV

Answer 15

Fluorescent microscopy