What are artifacts in microbiology?
An artifact in biology usually refers to experimental error or other spurious results. In the context of microbiology, you will get artifacts if, for example,  you sneeze on the plate you are growing a colony on. 

The term is generally used for any result that is not actually true but stems from bad analysis or experimental procedures. Take, for example, this definition from biology-online.com:


  Something artificial, a distortion that does not reflect normal anatomy or pathology, not usually found in the body. For example: in radiology, the appearance on an x-ray of a surgical metal clip that obscures the clear view of an anatomical structure.