Aseptic technique

Aseptic technique refers to a procedure that is performed under sterile conditions. This includes medical techniques and laboratory techniques, such as with microbiological cultures.

Additional recommended knowledge

Daily Visual Balance Check

How to quickly check pipettes?

What is the Correct Way to Check Repeatability in Balances?

Medical procedures

Aseptic technique is the effort taken to keep patients as free from hospital micro-organisms as possible (Crow 1989). The founder of the technique is considered to be Joseph Lister. It is a method used to prevent contamination of wounds and other susceptible sites by organisms that could cause infection. This can be achieved by ensuring that only sterile equipment and fluids are used during invasive medical and nursing procedures. Ayliffe et al. (2000) suggest that there are two types of asepsis: medical and surgical asepsis. Medical or clean asepsis reduces the number of organisms and prevents their spread; surgical or sterile asepsis includes procedures to eliminate micro-organisms from an area and is practised by nurses in operating theatres and treatment areas.

In microbiology

Aseptic technique is the name given to the procedures used by [microbiologist]]s to prevent microbial contamination of themselves, which may result in infection, contamination of the environment they are working in (e.g. fomites), and contamination of the specimen they are working on, which is especially important when a pure culture is desired. It is used whenever specimens are to be transferred between media, for example, when subculturing. Such a procedure, using a flame sterilization method, might occur as follows:  

1. A person would assemble the closed tube or flask from which—and the closed tube or flask to which—the specimen is to be transferred, an inoculating loop, and a fire source, all on a clean, preferably microbe-free surface with some overhead protection from airborne microbes.
2. The person would start the fire, and move the end of the inoculating loop, in a slow back-and-forth motion, through the top of the blue part of the flame. The person would not allow the loop to touch anything except the specimen itself, until the entire procedure is finished.
3. Preparing to execute the specimen transfer, the person would hold both of the tubes or flasks in one hand, typically the opposite of the writing hand. The person would then open the tube or flask containing the specimen source and briefly hold the top of it in the flame, to kill unwanted microbes.
4. Quickly, so as to minimize the possible time for contamination of the specimen in the source tube or flask, the person would use the inoculating loop with their writing hand to retrieve the specimen, and then sterilize the top of the tube or flask again before immediately closing it.
5. Keeping in mind that the specimen on the inoculating loop could be contaminated during every moment it is exposed, the person would repeat the previous step identically with the tube or flask in which the specimen is to be deposited; however, the person would be depositing the sample into the tube or flask.

Students of microbiology are taught the principles of aseptic technique by means of hands-on laboratory experience. Practice is essential in learning how to handle the laboratory tools without contaminating them.

References

• "MICROBIOLOGY: Classroom Assignment #2", a Portable Document Format computer file
• Microbiology Techniques & Troubleshooting
• Methods Manual – Applied Microbiology: Aseptic Technique

See also

• Antiseptic
• Cleanliness
• Body substance isolation