Any technique or procedure that prevents both the mixing of cultures and the contamination of worker and working area with pathogenic microbes or their toxins is called an aseptic technique.
When aseptic technique is not followed and contamination does occur, a condition of sepsis develops. In medically related situations, this term usually refers to an infection by disease-causing organisms or tissue damage due to the toxins produced by microbes.
Aseptic techniques must take into consideration both the work and the worker. Procedures that guarantee the complete absence of any living thing on material and equipment used in the laboratory are known as sterilization procedures and will be described shortly.
Procedures that ensure the absence of microbes from the worker are called safety precautions. All jobs have their unique hazards, and special precautions must be followed if the worker is to avoid being harmed on the job.
Working with microbes is no different except for the fact that the danger cannot always be seen. Therefore, it becomes essential to follow rules that will allow the person to control the location of the microbes in the working environment.
Lists several safety precautions that should be followed in a microbiology laboratory. However, each worker must develop an attitude about microbes and how they must be handled in the lab.
Once this “second sense” is developed, the aseptic techniques become a habit and are performed automatically. Until that time, it is essential to pay very close attention to each step performed. Probably the most basic of all procedures is called the transfer technique, or inoculation routine.
This procedure enables the safe movement of a microbe sample without contamination. Before a sample of broth culture is transferred, the test tube is examined to be sure the microbes are evenly distributed within the liquid medium.
If they have settled to the bottom, the microbes are mixed by “rolling” the tube between the hands. Never shake a liquid culture up and down with your thumb on top! Most test tube caps are designed to allow air to pass in and out of the tube but restrict the movement of microbes.
The fluid may be easily shaken out through this air space, or a mist of small airborne droplets known as an aerosol can move out through this gap. Once mixed, the top is removed (but not put down) and the test tube opening is passed through a Bunsen burner flame to kill all contaminants around the rim.
This action also begins a hot air current that moves microbes in the air away from the opening to prevent their accidentally falling into the tube. The inoculating loop is flamed and dipped into the culture.
A sample is carefully removed, so as not to touch the inside of the culture tube. If this accidentally happens, the culture may “flick” off the loop onto the working area or the worker. After the transfer is complete, both the loop and test tube are reflamed before the cap is replaced and the loop set down.
The greatest hazards of transferring microbes are that they become highly concentrated in culture. After a specimen has been taken, it is inoculated into a growth medium that contains all the necessary conditions for growth and reproduction; a few relatively innocent microbes become millions of potentially dangerous pathogens.
One, or even a few, of these microbes can be handled by the body’s defense mechanisms if it were to become infected; however, if thousands were to be accidently transferred this high number of microbes might cause severe disease. Many microbiologists have died as a result of laboratory accidents after they had become infected with the microbe they were studying.