Specimen Collection and Transport

General Principles - Collection Commandments

• Collect Before Antimicrobials: Maximizes pathogen yield.
• Aseptic Technique: Prevents contamination from normal flora.
• Appropriate Site & Quantity: Target infected area; collect sufficient material.
• Correct Container & Label: Use sterile, appropriate containers; label accurately (patient details, site, date, time).
• Prompt Transport: Ideally <2 hours to lab; use transport media if delay is unavoidable.
• Relevant Clinical Info: Provide history, suspected diagnosis to guide lab processing. 📌 6 Rights: Right Patient, Right Specimen, Right Time, Right Container, Right Transport, Right Label.

⭐ For blood cultures, collect 2-3 sets (20-30 mL per set for adults) from different venipuncture sites, ideally before fever spike or during chills.

Common Specimen Types - Sample Site Smarts

• Blood:
  • Site: Peripheral venipuncture.
  • Vol: Adults 10-20 mL/set; Paeds 1-5 mL.
  • Sets: 2-3, different sites, for sepsis.
  • Timing: Pre-antibiotics, febrile episodes.
• Urine:
  • Type: Mid-stream clean catch (MSU).
  • Preservative: Boric acid (>2h delay).
  • Vol: 10-20 mL.
• CSF:
  • Site: Lumbar puncture (L3-L4/L5).
  • Tubes (seq.): 1-Chem, 2-Micro, 3-Cells. 📌 Mnemonic: Chem Lab Cells.
  • Transport: STAT, room temp.

  ⭐ Never refrigerate CSF if N. meningitidis or H. influenzae suspected (cold-sensitive).

• Sputum:
  • Type: Deep cough.
  • Quality: >25 PMNs, <10 squamous/LPF.
• Stool:
  • Portion: Mucoid/bloody.
  • Preservative: Cary-Blair (bacteria), Formalin (O&P).
• Swabs (Throat, Wound, Genital):
  • Wound: Aspirates > swabs for pus. Advancing edge.
  • Transport: Amies/Stuart's (bacteria), VTM (viruses).

Transport Media & Conditions - Carry On, Microbes!

Maintain viability, prevent drying & overgrowth, no multiplication.

• Key Media:
  • Stuart's/Amies: General, fastidious (GC, H. influenzae). Charcoal neutralizes.
  • Cary-Blair: Faeces (Salmonella, Shigella, Vibrio, Campylobacter). pH 8.4.
  • VR Medium (Venkatraman-Ramakrishnan): Vibrio cholerae.
  • Pike's Medium: Streptococcus pyogenes (throat swabs).
  • VTM (Viral Transport Medium): Viruses. Contains protein, antibiotics. Store 4°C (short-term), -70°C (long-term).
• Temperature Conditions:
  • Most specimens: Room temperature or 2-8°C (refrigeration).
  • CSF (bacterial meningitis): Room temp. ⚠️ Avoid refrigeration for suspected N. meningitidis, H. influenzae (cold sensitive).
  • Urine for culture: Refrigerate at 4°C if delay >2 hours.
  • Blood culture bottles: Incubate at 37°C or room temp as per bottle type.
  • Anaerobic specimens: Room temperature.
• Anticoagulant (Blood Culture):
  • SPS (Sodium Polyanethol Sulfonate): Anticoagulant, antiphagocytic, neutralizes complement & some antibiotics.

📌 Cary Blair for Campylobacter & Cholera.

⭐ > For suspected Neisseria gonorrhoeae, swabs should ideally be plated directly onto selective media or transported in Amies medium with charcoal, reaching the lab within 6 hours.

Specimen Rejection - Gatekeeper's Guide

Crucial for reliable results. Common reasons for rejection:

• Identification: Mislabeled, unlabeled, or mismatched specimen/requisition form.
• Container & Transport: Incorrect, non-sterile, or leaking container. Wrong/no preservative. Improper temperature or prolonged transit (>2 hrs general rule; CSF <1 hr).
• Specimen Quality: Insufficient quantity (QNS). Obvious contamination (e.g., saliva in sputum: >25 Squamous Epithelial Cells/LPF). Dry swab. Specimen in fixative (for culture).

⭐ A 24-hour urine specimen for culture is generally unacceptable due to uncontrolled bacterial proliferation; timed collections are for chemistry.

High‑Yield Points - ⚡ Biggest Takeaways

• Blood cultures: Collect before antibiotics; 2-3 sets from different venipuncture sites.
• CSF: Transport immediately at room temperature; never refrigerate.
• Urine: Mid-stream clean catch; refrigerate if delayed >2 hours or use boric acid.
• Sputum for AFB: 3 early morning samples on consecutive days.
• Swabs: Use transport media (Stuart's/Amies) to prevent drying and maintain viability.
• Anaerobic samples: Collect from sterile sites; use anaerobic transport media.
• Accurate labeling is critical: patient ID, site, date/time_of_collection_