Amies Transport Medium (ATM), developed in 1967 by microbiologist Stuart Amies, is a semi-solid agar-based solution designed to preserve the viability and pathogenicity of clinical specimens during transit. Essential for bacteriology labs, it maintains microbial integrity without promoting replication, ensuring accurate culture results for swab-based samples.
Core Components & Mechanism
- Sodium Thioglycollate: Reduces oxygen tension, protecting anaerobes.
- Charcoal: Absorbs toxins and fatty acids that inhibit bacterial growth.
- Calcium Chloride: Boosts survival of fastidious pathogens (e.g., Neisseria gonorrhoeae).
- Phosphate Buffer: Stabilizes pH (7.2–7.4) in clinical specimens.
- Semi-Solid Agar: Limits oxygen diffusion and prevents desiccation.
Mechanism: Creates a non-nutritive environment that sustains organisms for 24–48 hours at room temperature.
Best Practices for Specimen Integrity
- Collection: Roll swabs vigorously over lesions; avoid environmental contamination.
- Transport:
- Insert swab into Amies medium immediately after collection.
- Break swab stick against the tube wall to seal.
- Refrigerate (2–8°C) if processing delays exceed 4 hours.
- Avoid:
- Freezing (−20°C), which lyses bacterial cells.
- Overfilling tubes (causes oxygen exposure).
- Using expired medium (charcoal degrades after 6 months).
Clinical Applications & Limitations
- Ideal for:
- Nasopharyngeal, wound, and genital swabs (Streptococcus, Corynebacterium, Neisseria).
- Aerobic and anaerobic bacteria preservation.
- Not suitable for:
- Viral samples (requires VTM with stabilizers).
- Fecal specimens (use Cary-Blair medium).
- Urine or blood cultures.
Report a question
Amies Transport Medium bridges clinical sampling and lab diagnostics. By mastering its chemistry, applications, and limitations, professionals safeguard specimen viability and ensure diagnostic reliability. Continual learning—through FAQs and self-assessment tools—empowers labs to combat pre-analytical errors that compromise patient outcomes.
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