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Microbiology

Transport Systems

This section provides an overview of the critical elements involved in specimen transport systems and conditions, focusing on transport devices, atmosphere, and time/temperature considerations. Proper specimen transport is essential for maintaining the viability and integrity of microorganisms, ensuring accurate and reliable laboratory results

Importance of Proper Specimen Transport

  • Maintaining Viability: Preserving the viability of microorganisms during transport is essential for accurate detection and identification
  • Preventing Overgrowth: Controlling the transport conditions can prevent the overgrowth of certain organisms, ensuring that the pathogens of interest can be detected
  • Preserving Specimen Integrity: Appropriate transport conditions help maintain the integrity of the specimen, preventing degradation or alteration of the microorganisms
  • Ensuring Accurate Results: Proper transport conditions are essential for obtaining accurate and reliable test results, which are critical for patient care

Transport Devices

  • General Requirements: Sterility, leak-proof design, appropriate medium, temperature control, and clear labeling
  • Types of Transport Devices
    • Swabs
      • Amies Transport Medium: Widely used for bacterial culture, available with or without charcoal
      • Liquid Amies Transport Medium: Suitable for automated specimen processing and molecular testing
      • Dacron or Rayon Swabs: Preferred over cotton swabs
    • Sterile Containers
      • Sterile Urine Containers: Available with or without preservatives
      • Sterile Specimen Cups: Used for stool, sputum, and tissue specimens
      • Anaerobic Transport Containers: Maintain an oxygen-free environment
    • Transport Media for Specific Organisms
      • Cary-Blair Medium: For transporting stool specimens for bacterial culture
      • Viral Transport Medium (VTM): For viral culture and molecular testing
      • Mycobacterial Transport Medium: Middlebrook 7H9 broth, Dubos broth
      • Fungal Transport Medium: Mycosel agar, Sabouraud dextrose agar
    • Blood Culture Bottles
      • Aerobic Bottles: For aerobic bacteria
      • Anaerobic Bottles: For anaerobic bacteria
      • Pediatric Bottles: For smaller blood volumes
  • Selection of Appropriate Transport Device: Consider the type of specimen, suspected organisms, testing requirements, and laboratory guidelines

Atmosphere

  • Importance: Different organisms have different atmospheric requirements for survival and growth
  • Types of Atmospheric Requirements
    • Aerobic: Requires the presence of oxygen
    • Anaerobic: Requires the absence of oxygen
    • Facultative Anaerobic: Can grow in the presence or absence of oxygen
    • Microaerophilic: Requires a reduced level of oxygen (5-10%)
    • Capnophilic: Requires an elevated level of carbon dioxide (5-10%)
  • Methods for Controlling Atmosphere During Transport
    • Aerobic Transport: Swabs in transport media, sterile containers with tight-fitting lids
    • Anaerobic Transport: Anaerobic transport vials and bags, minimize exposure to air
    • Microaerophilic Transport: Specialized transport media, gas-generating packets
    • Capnophilic Transport: Gas-generating packets, candle extinction jar
  • Specific Considerations
    • Wound Specimens: Anaerobic transport systems
    • Genital Specimens: Capnophilic environment for Neisseria gonorrhoeae
    • Gastrointestinal Specimens: Microaerophilic environment for Campylobacter
    • Respiratory Specimens: Capnophilic environment for Streptococcus pneumoniae or Haemophilus influenzae

Time and Temperature

  • Importance: Time and temperature are critical for maintaining the viability and integrity of microorganisms during transport
  • General Guidelines
    • Minimize transport time
    • Maintain appropriate temperature
    • Follow laboratory guidelines
    • Document deviations
  • Temperature Ranges
    • Refrigerated (2-8°C): For many bacterial, viral, and fungal specimens
    • Room Temperature (20-25°C): For some bacterial specimens and specimens where refrigeration may be detrimental
    • Frozen (-20°C or -70°C): For long-term storage of certain viral and molecular specimens
    • Body Temperature (35-37°C): For some fastidious organisms and blood cultures
  • Specific Recommendations
    • Bacterial Specimens: Transport most at refrigerated temperatures (2-8°C) within 24-72 hours; Neisseria gonorrhoeae at room temperature or body temperature within 6 hours
    • Viral Specimens: Transport most at refrigerated temperatures (2-8°C) within 48 hours; for long-term storage, freeze at -70°C
    • Fungal Specimens: Transport most at room temperature (20-25°C) or refrigerated temperatures (2-8°C) within 24-72 hours
    • Mycobacterial Specimens: Transport at refrigerated temperatures (2-8°C) within 24 hours
    • Blood Cultures: Transport at body temperature (35-37°C) or room temperature (20-25°C) as soon as possible; do not refrigerate
    • Urine Specimens: Transport at refrigerated temperatures (2-8°C) within 24 hours; unpreserved urine within 2 hours

Common Errors and How to Avoid Them

  • Using expired transport devices
  • Improper storage of transport devices
  • Overfilling or underfilling transport devices
  • Delay in transport
  • Failure to label
  • Improper use of anaerobic transport systems
  • Exposure to air
  • Failure to use appropriate transport media
  • Refrigerating blood cultures
  • Failure to document deviations

Key Takeaways

  • Proper specimen transport is critical for accurate and reliable laboratory results
  • Transport devices, atmosphere, and time/temperature considerations are essential components of specimen transport
  • Adherence to recommended guidelines and laboratory protocols is crucial for maintaining the viability and integrity of microorganisms
  • Continuous training and monitoring are necessary to ensure that personnel are following proper specimen transport procedures