General Considerations for Specimen Collection

Study Notes

Collect specimens prior to the administration of antibiotics.
Collect specimens at the infection site for accurate results.
Employ aseptic techniques during specimen collection to avoid contamination.
Consider timing; for viral infections, collect specimens within 2-3 days of illness onset.
In typhoid fever, blood cultures are positive in the first week, while stool cultures remain negative during this period.
Provide clear instructions to patients on sample collection.
Use appropriate containers and transport media; obtain a sufficient quantity of the specimen.
Clearly label specimens with accurate patient and specimen information.

Level 1 (Critical/Invasive): Includes blood, amniotic fluid, cerebrospinal fluid (CSF), brain, heart valves, and pericardial fluid.
Level 2 (Unpreserved/Without Preservatives): Comprises bone, feces, sputum, tissue, and body fluids that may contain normal flora.
Level 3 (Quantitation Required): Involves specimens like catheter tips, urine, and tissues needing quantitation.
Level 4 (Preserved/With Preservatives): Includes urine, feces, and swabs transported in holding media.
Level 5 (Batch Processing): Involves sputum for acid-fast bacilli (AFB) culture.

Maintain specimens close to their original state for viability.
Fastidious organisms may not survive transport in nutritionally poor media.
Transport anaerobic bacteria samples within 10 minutes to retain viability; CSF samples should be transported within 15 minutes.
Certain microorganisms (e.g., Neisseria gonorrhoeae) are temperature-sensitive, while Shigella is pH-sensitive.

Stuart’s Medium (1954):
- Designed for N. gonorrhoeae transport with charcoal-impregnated swabs, though this can complicate Gram staining.
- Acts as a non-nutritive medium suitable for most specimens, including stool.
Amies Medium (1965):
- A modified Stuart’s medium that replaces glycerophosphate with a balanced salt solution while retaining charcoal within the medium.
- Improved transport capabilities for respiratory and stool specimens.
Cary & Blair Medium (1964):
- Similar to Stuart’s but optimized for fecal specimens with a higher pH (8.4) and no charcoal.
- Recommended for stool samples suspected for Campylobacter spp. and other enteric pathogens.
Buffered Glycerol Saline:
- Specifically designed for stool specimens with a high pH to favor growth of fecal pathogens.
- Not suitable for samples suspected of containing Campylobacter spp. due to toxicity.

Immediate or Room Temperature:
- Transport body fluids, bone, CSF, inner ear samples, corneal scrapings, gastric aspirates at room temperature.
Within 24 hours/Room Temperature:
- Includes abscess samples, outer ear, conjunctiva, genital tract specimens (prostate), urine (urethral), hair, nails, skin scrapings, respiratory samples.
Within 2 hours/Room Temperature:
- Necessary for blood or bone marrow specimens.
Within 24 hours/4°C:
- Recommended for rectal swabs, stool cultures, clean voided midstream urine.
Within 2 hours/4°C:
- Suitable for urine specimens from indwelling or straight catheters.
Immediate/4°C:
- Gastric biopsy specimens should be transported without delay.