gram-positive [Hans C.J. Gram; L, positivus] , retaining the violet color of the stain used in Gram’s method of staining microorganisms. This property is a primary method of characterizing organisms in microbiology. Some of the most common kinds of gram-positive pathogenic bacteria are Bacillus anthracis, Clostridium species, Mycobacterium leprae, Mycobacterium tuberculosis, Staphylococcus aureus, Streptococcus pneumoniae, and Streptococcus pyogenes.
