Gram-positive Streptococcus [purple cocciforms] and Gram-negative E. coli [red coliforms]. The Gram stain is named for Hans Christian Gram (1853 - 1938), who first described the method in 1884. The Gram stain is widely used as a rapid, initial diagnosis for the presence of Gram-positive micro-organisms, many of which are pathogenic. The Gram method uses an initial stain of crystal violet counter-stained with safranin.

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