Laboratory Lab results are too important to go anywhere else.

Specimen Collection Manual: Tissue or Wound/Lesion, Fluid Collection - Bacterial, Fungal, AFB

Department

Microbiology

Instructions

Tissue, aspirates, and fluids are always superior to a swab specimen. Collect specimens only after the wound has been cleansed and debrided and prior to initiating antibiotic therapy.

Materials/Supplies

• Sterile non-bacteriostatic saline.
• Sterile syringes.
• Sterile screw-capped collection containers.
• ESwab collection device.

Wound/Lesion (Skin, Sub-Cutaneous) Site Preparation Instructions

• Decontaminate the site with surgical soap and 70% ethyl or isopropyl alcohol.
• Rinse the wound well with sterile, non-bacteriostatic saline and allow to dry.

Specimen Collection Criteria

Closed Abscesses or Body Fluids

• Thoroughly disinfect skin with 70% ethyl or isopropyl alcohol. Aspirate infected material with needle and syringe. If the initial aspiration fails to obtain material, inject sterile non-bacteriostatic saline subcutaneously and repeat the aspiration attempt. Place fluid contents into a sterile screw-capped collection container or send the sterile sealed syringe (without the needle) to the laboratory.

Open Wounds

• Cleanse the wound margins and superficial area thoroughly with sterile saline, changing sponges with each application. Remove all surface debris or superficial exudate using a scalpel, swabs, or sponges to prevent specimen contamination. Collect a biopsy or curette sample from the base or advancing margin of the lesion. Collect sufficient tissue (5-10 mm3) and avoid collecting tissue from necrotic areas. Place tissue in a sterile container with a few drops of non-bacteriostatic saline (just enough to keep the specimen from drying out).

Pus or Purulent Exudate

• Avoid collecting pus located on intact skin and aspirate pus from the deepest portion of the lesion using a needle and syringe. Submit pus in a sterile screw-capped collection container. Also collect a biopsy sample of the advancing margin or base of the infected lesion after excision and drainage (see above).

Swabs

• Collect swabs only when tissue or fluid cannot be obtained. Limit swab sampling to wounds that are clinically infected or those that are chronic and are not healing. To minimize contamination, it is important to cleanse the wound to remove superficial debris by thorough irrigation and cleansing with non-bacteriostatic sterile saline. Insert the tip of the swab into the depths of the wound/lesion and gently rotate the tip of the swab in the wound for 5 seconds. Apply enough pressure to express fluid from the wound tissue. Place the swab in transport media and send to the laboratory.

Minimum Specimen Requirements*

Type of Culture	Specimen Type	Minimum Quantity
Anaerobic	Sterile Fluid	1.0 mL
Anaerobic	Sterile Tissue	5-10 mm3
Aerobic	Sterile Fluid (Not CSF)	2-4 mL (AFB requires another 5 mL)
Aerobic	Sterile Tissue	5-10 mm3

Rejection Criteria

• Do not submit tissues for culture in formalin, or in containers that ever contained formalin.
• Do not use expired media. Check expiration date on all media prior to use.
• Swab specimens are unacceptable for AFB Cultures.

In-Lab Processing

If the specimen is for:	Then:
Tissue	Small tissue specimens should be placed into an ESwab container. Large specimens must be submitted in a sterile collection container
Fluid	Fluid specimens must be submitted in a sterile collection container. Do NOT add saline with fluid specimens. Do NOT submit swab specimens.
Wound	Place ESwab in an appropriate transport medium.

• Send specimens to the Laboratory at room temperature (20-26°C or 68-78.8°F). Do not freeze. If longer delays are anticipated for tissue or fluid specimens (greater than 24 hours), specimens should be frozen at -70°C.

Reference

*Lynne S. Garcia, Editor-in-Chief. Specimen Collection, Transport, and Acceptability, Clinical Microbiology Procedures Handbook, 3^rd Edition. ASM Press. Washington, D.C., 2010.

Contacts

Last Updated

1/5/2023