Selection, Collection, and Transportation of Specimens for Microbiological Examination

Goal of the Laboratory: The primary role of the laboratory in the diagnosis of infections is considered a major step in diagnostic microbiology.
Success Factors for Pathogen Isolation: For pathogens to be isolated successfully, several factors must be correct: * The type of specimen selected. * The method and accuracy of its collection. * The timing of specimen collection. * The method used to send the specimen to the laboratory.
Importance of the Request Form: A request form accompanying the patient's sample is vital as it assists the laboratory in selecting the appropriate tests to perform.

Supporting clinical information and documentation on the request form should include the following eight items:

Patient Details: Full identifying information of the patient.
Clinical Diagnosis: The suspected or confirmed diagnosis given by the clinician.
Onset of Symptoms: The specific time or date when symptoms first appeared.
Sample Type: The nature of the specimen being submitted.
Time of Collection: The exact time the specimen was taken from the patient.
Treatment History: Full details regarding treatment history and concurrent antimicrobial therapy.
Safety Issues: Other health and safety concerns, such as high-risk infections.
Supporting Clinical Context: Vital information including travel history and known contact with infected individuals.

Integrity of Investigation: Microbiological investigations require careful collection to prevent contamination from external sources or the patient's own commensal flora.
Container Specifications: Clinicians must use sterile, leak-proof containers for all samples.
Labeling: Every specimen must be labeled correctly and clearly.
Management of Normal Flora: Great care must be taken when obtaining samples through areas containing normal flora. For example, during a vein puncture through the skin to obtain a blood culture, the skin must be decontaminated with an appropriate antiseptic prior to collection.
Timing Relative to Therapy: Whenever possible, specimens for microbiological culture must be taken prior to the beginning of antibiotic therapy to avoid false-negative results.

Specimens collected for microbiology include, but are not limited to:

Key Measures for Accuracy: * Utilization of appropriate transport media. * Execution of proper handling, labeling, and transportation protocols. * Selection of the specific container suitable for the specimen type. * Clear communication and instructions provided to the patient prior to collection. * Rigorous avoidance of contamination during collection and handling processes.
Temporal Requirements: Rapid transport of samples to the microbiology laboratory is essential and should ideally occur within $2\,hours$ of collection.
Risks of Delayed Transport: * Loss of Viability: Many fastidious microorganisms may die during transit. Specific examples include $Neisseria\,gonorrhoeae$ and $Haemophilus\,influenzae$ . * Flora Overgrowth: Contaminating normal flora may overgrow, confusing the identification of the actual pathogen.

Microbiology departments adopt several strategies to ensure specimen stability:

Transit Speed: Specimen should reach the laboratory as soon as possible; otherwise, a suitable preservative or transport medium must be employed.
Refrigeration: Storing unpreserved specimens at $4\,^{\circ}C$ can preserve cells and reduce the multiplication of commensal organisms.
Freezing: Long-term preservation may require freezing at $-70\,^{\circ}C$ or below in the presence of a stabilizing fluid, such as glycerol or serum.
Container Integrity: Containers must be inspected to ensure they are free from cracks and that caps are leak-proof.
Sealing: Caps should be sealed with adhesive tape to prevent loosening and leakage during transit.
Protective Packaging: If glass tubes or bottles are used, sufficient packaging material must be included to protect the specimen from breakage.
Absorbent Material: For fluid specimens, sufficient absorbent material must be included to soak up the liquid in case of a leak.
Warning Labels: All specimens potentially containing highly infectious organisms must be explicitly marked as "HIGH RISK."

Faeces (Stool): Collected in a Universal container that includes a spoon attached to the inside of the screw cap.
Urine: * Small Quantities: A standard Universal container is suitable. * Large Volumes: $250\,mL$ wide-mouthed screw-capped bottles are recommended.
Sputum: A Universal container should not be used. Instead, squat, wide-mouthed disposable containers are required.
Blood: * Without Anticoagulant: Used for serological examinations, including antibody or antigen detection. * With EDTA Anticoagulant: Used for parasitological examinations, such as malaria blood films.
Serous Fluids: * Collected in a Universal container. * For fluids that may coagulate upon standing, the addition of $0.3\,mL$ of a $20\%$ sodium citrate solution to the container prior to autoclaving (with cap fitted) is recommended. * This prevents clot formation and facilitates accurate cell counting and centrifugation.
Blood Culture Bottle: * Must have a capacity large enough to hold at least $50\,mL$ of liquid culture medium (prepared by the lab). * Requires an additional $5-10\,mL$ of the patient's blood to be inoculated into the medium.

Primary Application: Swabs are suitable for collecting exudates from the throat, nostrils, ear, skin, wounds, and other accessible lesions.
Special Purpose Swabs: 1. Baby swabs. 2. Paranasal swabs. 3. Post-nasal swabs. 4. Laryngeal swabs. 5. High vaginal and cervical swabs. 6. Serum-coated cotton wool swabs.

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