Specimen Collection and Transport
Specimen collection and transport decide whether the laboratory receives the right material in a condition that can answer the clinical question.
Core idea
Many microbiology errors start before the specimen reaches the bench. Good collection protects the patient from false reassurance, misleading mixed growth, and unnecessary repeat testing.
Principle
The specimen should come from the infected site, avoid avoidable contamination, arrive quickly, and use transport conditions that preserve the organism being sought.
Common Specimen Priorities
| Specimen | Collection priority | Why it matters |
|---|---|---|
| Blood culture | Separate venipuncture sites and adequate volume | Helps separate true bacteremia from contamination |
| CSF | Prompt delivery in sterile tubes | Organisms and cells can decline quickly |
| Respiratory specimen | Deep lower respiratory sample when pneumonia is suspected | Saliva-heavy specimens mostly reflect oral flora |
| GI specimen | Fresh stool or approved transport/preservative when indicated | Timing and preservative affect bacterial and parasite recovery |
| Urine | Clean-catch, catheterized, or suprapubic specimen as clinically appropriate | Collection method changes colony count interpretation |
| Wound or abscess | Aspirate or tissue from the active process | Surface swabs can overrepresent colonizers |
Basic workflow
- Match the specimen to the syndrome and suspected organism group.
- Use a sterile container or appropriate transport system.
- Collect enough material before antimicrobial therapy when possible.
- Label source precisely, not just the body region.
- Deliver promptly or use the required transport medium.
How to read it
- A deep aspirate usually has more value than a superficial swab.
- Blood cultures are interpreted by organism identity, number of positive bottles, and collection pattern.
- Anaerobic workups need specimen types and transport that protect organisms from oxygen.
High-yield trapCommon mistakes
- Submitting superficial swabs for deep infections.
- Using vague source labels such as wound or drainage.
- Letting low-volume or fragile specimens sit too long.
ShortcutStudent shortcut
Specimen first, organism second. A poor specimen makes every downstream answer weaker.