Safe Handling of Microbiology Samples

• What is the primary aim of collecting clinical samples for microbiology testing?

  To correctly identify the pathogen, provide a diagnosis, and advise on appropriate therapy
• What is a pathogen?


  An organism that has the ability to grow in the body and initiate disease
• Why is the quality of the sample important in microbiology testing?


  It is crucial for the accurate identification of the pathogen
• What are the considerations for sample collection to avoid contamination?


  • Clean the collection site (e.g., use alcohol-based disinfectant)
  • Only trained staff should collect samples
  • Use appropriate samples (e.g., mid-stream urine)
  • Use sterile, approved specimen containers
• How can contamination during sample collection be avoided?


  By cleaning the collection site and using sterile containers
• When should samples be collected to maximize organism recovery?


  At an appropriate time, such as during a temperature spike in sepsis
• What type of blood sample is not appropriate for the isolation of bacteria?


  A blood sample in a plain collection tube
• Why might multiple samples be required for diagnosis?

  To ensure a reliable diagnosis
• What is a common specimen container for mid-stream urine?

  Sterile universal pot
• What are commonly used specimen swabs in microbiology?

  • General transport swab (Amies Agar)
  • Wound swabs
  • Throat swabs
  • High vaginal swabs (HVS)
• What is the purpose of using transport medium in specimen swabs?

  To maintain organism viability and absorb toxins
• What type of blood culture containers are typically used?

  Aerobic and anaerobic bottles
• What happens if the volume of blood collected for culture is incorrect?

  Too little may reduce the chance of organism recovery, while too much may lead to false positives
• What are the requirements for transporting samples to the laboratory?

  • Fully labelled
  • Maintained at correct temperatures (4°C or 37°C)
  • Delivered timely for processing
  • Correctly packaged to avoid leakage or contamination
• What legal regulations apply to the transport of specimens considered dangerous goods?

  COSHH and Health and Safety at Work Act (1974)
• What are the two categories of infectious substances?


  • Category A: Capable of causing permanent disability or fatal disease
  • Category B: Does not meet criteria for Category A
• Give examples of Category A infectious substances.

  Bacillus anthracis, Yersinia pestis, Ebola, and West Nile viruses
• What is the proper shipping name for Category B infectious substances?


  "Biological substance, Category B"
• What is the basic sample processing overview in the diagnostic lab?

  1. Sample arrives in specimen reception
  2. Sample checked, logged, and barcoded
  3. Sent to relevant area for processing
• Why is microscopy sometimes not useful for certain samples?

  Because swabs and fluids may need to be inoculated directly onto a slide
• What is a widely used staining method in microscopy?

  Gram stain
• What is the purpose of using wet preparations in microscopy?

  To detect parasites by observing samples under a coverslip
• What is the Ziehl-Neelsen stain used for?

  Mycobacterium tuberculosis
• What are the reasons for culturing a sample on agar plates?

  • Investigate if an organism is present
  • Investigate if there is more than one organism
  • Obtain a presumptive identification based on phenotype
  • Have an isolate available for further testing
• How do you inoculate agar plates?

  By using techniques like streak plating to isolate single colonies
• Why is it important to use more than one agar type for culturing?

  Because not all organisms have the same growth requirements
• What is the purpose of inoculating agar plates?

  To culture the sample and investigate the presence of organisms.
• Why is it important to investigate if there is more than one organism present in a sample?

  To obtain a presumptive identification based on the phenotype.
• How do you inoculate agar plates to allow individual colonies to be observed?

  By using techniques such as streak plating or spreading.
• What is the aim of isolating single colonies on agar plates?

  To allow for the detection of mixed cultures.
• What is the significance of using more than one agar type in culturing organisms?

  Not all organisms have the same growth requirements.
• What are selective agars used for?

  To prevent the growth of some organisms while aiding the growth of a target pathogen.
• How do differential agars help in identifying different species?

  They allow distinction based on biochemical reactions.
• What is an example of a selective antibiotic used in agar plates?

  Aztreonam.
• What does the pink color of E. coli on MacConkey agar indicate?

  Lactose fermentation.
• What is the appearance of non-lactose fermenting Proteus mirabilis on MacConkey agar?

  Colourless.
• What is the purpose of chromogenic media?

  To differentiate common UTI pathogens.
• Why is the order of plate inoculation important?

  To prevent contamination and ensure accurate results.
• What are the four Hazard Groups for organisms?

  1 to 4.
• What is Hazard Group 1 classified as?

  A biological agent unlikely to cause disease.