CA - Sample Collection, Diagnosis & Result Interpretation (TTY) Wk 1

Question 1

• gram +ve vs -ve bacteria - cant find
• types of body sites??

Answer 1

READ

Specific swabs that should be used for specific tests include:

1. Viral culture
   Swab that contains universal transport media (UTM) or viral transport media (VTM)
2. Anaerobic culture
   Swab that contains transport media for bacteria (e.g. gel swab, eSwab)
3. PCR
   A dry swab or swab that contains UTM
4. Aerobic culture
   Dry swab, or gel-swab, or eSwab

Question 2

What are main types of microbiology tests?

Answer 2

CULTURE: aerobic culture, anaerobic culture (to grow fastidious organisms that only survive without oxygen),
fungal culture (specific to grow only fungal organisms),
viral culture (specific to culture only
viruses),
mycobacterial culture (specific to grow only mycobacteria, which include Mycobacterium
tuberculosis)

SEROLOGY: test for antibodies formed by the body in response to infection.
Usually to detect past or recent
infection, sometimes can be used to detect acute infection

PCR: special technique to detect the nucleic acid (DNA, RNA) of infecting organisms

MICROSCOPY: to visualize microorganisms under microscope, often using special stains

Question 3

What is the swab type used for bacteria culture? What is it suitable & not suitable for?

Answer 3

Rayon bud (tip) with plastic shaft and
Amies transport medium

Suitable for
1. Aerobic/Anaerobic culture
2. Screening (e.g. MRSA)

NOT suitable for
1. Bacterial PCR
2. Viral PCR / culture

Question 4

What is the swab type used for Viral culture & Viral PCR? What is it suitable & not suitable for?

Answer 4

Flocked swab with Universal Transport Media (UTM)

Suitable for
1. Viral culture, antigen & PCR (influenza)
2. Chlamydial PCR

NOT suitable for
1. Bacterial PCR
2. Aerobic/Anaerobic culture

Question 5

What is the swab type used for bacterial culture and bacterial PCR? What is it suitable & not suitable for?

Answer 5

Flocked swab with liquid Amies media

Suitable for
1. Aerobic/Anaerobic Culture
2. Bacterial PCR (e.g. MRSA)
3. Screening (e.g. MRSA)
4. Viral PCR/culture

Question 6

How to collect a Catheter specimen urine CSU?

Answer 6

1. If required, clamp the tubing a few cm distal to the sampling port.
2. Clean the sampling port.
3. Sample from the sampling port.
4. Aspirate the required amount of urine into the syringe.
5. Inject urine into the specimen pot.

Question 7

What are the steps for collecting sputum?

Answer 7

1. Collect in the morning
2. Before breakfast (to avoid contamination with food particles)
3. Rinse with water (not mouthwash /
   toothpaste)
4. Sit patient up
5. Ask the patient to take several deep breaths – breathing in through the nose and exhaling though the mouth – to help loosen secretions
6. Ask patient to hold his/her breath a few seconds - then cough directly into the specimen container

Question 8

What are the principles of collection of samples for the diagnosis of infective pneumonia?

Answer 8

1. obtain a specimen from the lungs, as far as possible
2. reduce contamination from mouth and throa

Question 9

How long does it take for results from the laboratory to come back?

Answer 9

Blood tests
1-3 days

Microscopy
1-2 days

PCR
1-3 days

Aerobic culture
2-5 days

Viral culture
7-21 days

TB culture
10-42 days

Question 10

2 Interpretations of microbiology results for sterile body sites?

Answer 10

1. Infection
   The bacteria is present and invading the body, causing signs and symptoms of infection.
2. Contamination
   Defined as “growing organisms that are not from the intended site culture”
   - to collect the sterile sample, we need to pass through a non-sterile site
   - to collect a blood culture,
   we need to collect the blood via a needle that passes through the skin.
   Bacteria from contaminated samples are not really present in the sterile sample, but originate from the sampling technique or a superficial site
   -in a contaminated blood culture, the organisms are not in the blood, but originate from the skin (where the collection needle was contaminated).

Question 11

3 Interpretation of microbiology results for non-sterile sites?

Answer 11

1. Infection
2. Contamination
3. Colonisation
   This is defined as “growing organisms that are unlikely to cause infection, or growing organisms without signs of infection”.
   - if we take a swab from the nose of a healthy human, we may grow Staph aureus,
   - but in the absence of signs of infection, this would be colonisation.