M13

Question 1

What are the principles of how organisms can be detected in clinical specimens?

Answer 1

microscopy, culture, molecular

Question 2

Name common stains used for microscopy

Answer 2

• Gram stains

- Acid fast stains: Ziehl Neelsen, Auramine Fluorescent, Immunofluorescence/Labelled antibodies

Question 3

What type of organisms that can be detected using common stains used for microscopy?

Answer 3

• Mycobacteria primarily
• Immunofluorescence/Labelled antibodies:Detect antigen in clinical material, Can be operator dependent e.g. Legionella, Chlamydia, some viruses, Pneumocystis

Question 4

How are cultures used to detect microorganisms?

Answer 4

• Grow organisms to detect and identify them

- pure culture needed for ID and susceptibility testing

Question 5

What are the types of cultures used to detect microorganisms?

Answer 5

• Agar

- Broth

Question 6

What is agar?

Answer 6

Solid, like a firm jelly
Derived from red algae 
Can see colonies
Easier to work with many different types of agar
Selective and differential

Question 7

What is broth?

Answer 7

• Liquid medium
• More sensitive: i.e. able to detect smaller numbers of organisms
• Need to subculture onto solid media prior to identification

Question 8

What is molecular detection?

Answer 8

• Look for presence of organism’s nucleic acid: DNA/RNA

- Very sensitive – can detect small numbers of organisms

Question 9

What are the methods of molecular detection?

Answer 9

• Polymerase chain reaction (PCR) or similar

- Multiple nucleic acid amplification techniques are available

Question 10

Name some of the common clinical samples that can be submitted to the microbiology lab

Answer 10

• urine
• pus and swabs
• swabs
• tissue
• sputum
• stool

Question 11

Name samples that have normal flora

Answer 11

• Sputum
• Vaginal swabs
• Superficial swabs
• Urine (if poorly collected) and/or stool

Question 12

Name samples that do not have normal flora

Answer 12

• Blood
• CSF
• Pleural, pericardial, peritoneal
• Tissue (deep)

Question 13

What is the difference between samples that have/do not have normal flora?

Answer 13

• Samples containing normal flora are non-sterile

- Sample that do not contain normal flora are obtained from sterile sites and are more helpful