germfree
Meaning of germfree: A laboratory condition rather than a hospital one: free not merely of germs that cause disease but of every detectable microbe.
Definition of germfree
Germfree describes an animal, or an enclosure, in which no living microorganism of any kind can be detected. That includes the harmless bacteria normally coating skin and lining the gut, not only those able to cause illness. Germfree animals are delivered by sterile surgery and reared in sealed isolators on sterilized food and filtered air, and the state is a research tool rather than a clinical one.
How is a germfree animal produced?
The young are delivered surgically into a sterile chamber, so they never pass through the birth canal or meet their mother's skin, and they are raised inside a sealed isolator handled through gloved ports. Every item entering is heat treated or filtered, and air is filtered coming and going. The status is not assumed but tested, repeatedly, by culturing droppings and by searching them for bacterial genetic material, since a claim of no organisms is only as strong as the methods used to look. A single species of bacteria slipping in ends the experiment.
What is different about an animal with no microbes?
A great deal, which is precisely the finding. The immune tissue lining the gut stays sparse and immature, fewer antibody-producing cells develop, and the part of the large bowel where microbes normally ferment fiber swells enormously because nothing is fermenting there. More food is needed for the same growth, since resident organisms normally break down material the animal cannot. Some vitamins made by gut bacteria have to be supplied instead. Such animals prove unusually vulnerable to infection, yet oddly protected from certain inflammatory injuries. Together these findings established that the resident population is not a set of passengers but a participant in building the body that hosts it.
What do the neighboring terms mean?
| Term | What it describes |
|---|---|
| Germfree, or axenic | No microorganism of any kind detectable |
| Gnotobiotic | Only a known set of organisms, deliberately introduced |
| Specific pathogen free | Free of a named list of harmful organisms; others present |
| Conventional | The ordinary mixed population |
No person is germfree, and the word is misapplied in advertising for cleaning products. Colonization starts at birth and a mixed population is carried for life, most of it harmless or useful. Protective isolation for someone with very low white cell counts reduces what reaches that person and lowers the chance of an opportunistic infection, but it does not clear the organisms already living on and inside the body.
Also known as
Used in a sentence
The experiment compared germfree animals with those carrying a normal gut population.
Good to know
Germfree is defined by the absence of all detectable microorganisms rather than of harmful ones alone, and it applies to animals raised in isolators, since no person or ordinary environment reaches that state.