Specimen Collection and Transport of Anaerobic Bacteriology
المؤلف:
Patricia M. Tille, PhD, MLS(ASCP)
المصدر:
Bailey & Scotts Diagnostic Microbiology
الجزء والصفحة:
13th Edition , p458-460
2025-08-25
602
The importance of proper collection and transport of specimens for anaerobic culture cannot be overemphasized. Because indigenous anaerobes are often present in large numbers as normal flora on mucosal surfaces, even minimal contamination of a specimen can produce misleading results. Box 1 shows the specimens accept able for anaerobic culture; Box 2 presents specimens that are likely to be contaminated and therefore are unacceptable for anaerobic culture. In general, material for anaerobic culture is best obtained by tissue biopsy or by aspiration using a needle and syringe. Use of swabs is a poor alternative because of excessive exposure of the specimen to the deleterious effects of drying, the possibility of contamination during collection, and the easy retention of microorganisms in the fibers of the swab. If a swab must be used, it should be from an oxygen-free transport system.
Box1. Clinical Specimens Suitable for Anaerobic Culture
Box2. Clinical Specimens Unsuitable for Anaerobic Culture
A crucial factor in obtaining valid results with anaerobic cultures is the transport of the specimen; the lethal effect of atmospheric oxygen must be nullified until the specimen can be processed in the laboratory. Recapping a syringe and transporting the needle and syringe to the laboratory is no longer acceptable because of safety concerns involving needle stick injuries. Therefore, even aspirates must be injected into an oxygen-free transport tube or vial.
Three kinds of anaerobic transport systems are shown in Figures 1 to 3. Figure 1 shows is a rubber stoppered collection vial containing an agar indicator system. The vial is gassed out with oxygen-free carbon dioxide (CO2) or nitrogen. The specimen (pus, body fluid, or other liquid material) is injected through the rubber stopper after all air has been expelled from the syringe and needle. If only a swab specimen can be obtained, a special collection device with an oxygen free atmosphere is required (see Figure 2). When the swab is reinserted, care must be taken not to tip the container, which would cause the oxygen-free CO2 or nitrogen to spill out and be displaced by ambient air. A tissue specimen can be immersed in a small amount of liquid to prevent it from drying and then placed in an anaerobic pouch (see Figure3). All specimens should be held at room temperature pending processing in the laboratory, because refrigeration can oxygenate the specimen.
Fig1. Anaerobic transport system for liquid specimens. The specimen is injected into the tube through the rubber septum. Agar at the bottom contains an oxygen tension indicator. (Courtesy BD Diagnostic Systems, Sparks, Md.)
Fig2. Anaerobic transport system for swab specimens: Vacutainer Anaerobic Specimen Collector (BD Diagnostic Systems, Sparks, Md.). The sterile pack contains a sterile swab and an oxygen-free inner tube. After the specimen has been collected, the swab is inserted back into the inner tube. Agar on the bottom of the outer tube contains an oxygen tension indicator. .
Fig3. Anaerobic transport system for tissue specimens. Tissue is placed in a small amount of saline to keep it moist. It then is inserted into a self-contained, atmosphere-generating anaerobic bag for transportation. This system is called the GasPak Pouch. (Courtesy BD Diagnostic Systems, Sparks, Md.)
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