Hans Christian Joachim GRAM. Microbiólogo y médico danés nacido en Copenhague, 1853-1938. La vida e investigación de Gram transcurre en Copenhague, donde fue profesor de patología y terapéutica en la univerisidad de dicha ciudad. En 1884, durante su viaje a Berlín, diseñó y presentó el método microbiológico de tinción de bacterias que lleva su nombre. Se compone de yodo, yoduro potásico y agua, y permite teñir determinados elementos por contraste con otros o con el fondo. El método de Gram permite clasificar a las bacterias en dos tipos fundamentales, grampositivas y gramnegativas. La diferencia entre bacterias grampositivas y gramnegativas está en función de si retienen o no el colorante cristal violeta después de una serie de tratamientos. Esto permite permite averiguar que tipo de pared celular tienen las bacterias. Otros microorganismos también responden a este tipo de tinciones, como por ejemplo las levaduras, que son grampositivas y las rickettsias, que son gramnegativas.
   <(F.):Hans Christian Joachim GRAM, pharmacologue et pathologiste danois, né le 13 septembre 1853 à Copenhague, mort le 14 novembre 1938. On lui doit la coloration de Gram pour la détermination des bactéries.
   <(In.): Hans Christian Joachim Gram was a Danish physician and bacteriologist who developed a method of staining cells for microscopic study. Gram was born in Copenhagen, Denmark, on September 13, 1853. He received a B.A. in the natural sciences from the Copenhagen Metropolitan School in 1871 and served as an assistant to the zoologist Japetus Steenstrup from 1873-1874. He subsequently became interested in medicine and earned a medical degree from the University of Copenhagen in 1878. Gram, who worked in several areas of science and medicine, earned a gold medal in 1882 for a study on human erythrocytes. The following year he received a doctoral degree for his work in this field After obtaining his degree, Gram pursued post-doctoral studies in Berlin, focusing on bacteriology and pharmacology and pursuing post-doctoral studies in Berlin. It was in Berlin, in 1884, that he published his work on staining cells, which became widely known as Gram staining. At that time, the method of staining cells was not entirely new to scientific research and several methods were already being used. Gram borrowed from a procedure initially devised by Paul Ehrlich, who used alkaline aniline solutions to stain bacteria cells. Experimenting with pneumococci bacteria, Gram first applied Gentian violet, which stained the cells purple, and then washed the cells with Lugol's solution (iodine), which served as a mordant to fix the dye. He followed those steps by applying alcohol, which washed away any dye that was not permanently fixed. Gram found that some cells remained purple (Gram positive), while others stayed essentially unstained (Gram negative). Gram's method aided microscopic study of bacteria, as well as provided a means of differentiating and classifying bacteria cells. Several years later, the pathologist Carl Weigart improved upon Gram's method by adding another staining step, which consisted in dyeing the Gram negative cells with saffranine. Gram remained in Berlin working as an assistant in a hospital until 1891, when he was appointed as a professor of pharmacology at the University of Copenhagen. In 1889, Gram married Louise I. C. Lohse, and in 1892, advanced to the position of chief of internal medicine at the Royal Frederiks Hospital. Extremely active in the field of medical education, Gram also maintained a large internal medicine practice. From 1901-1921, Gram served as chairman of the Pharmacopoeia Commission, during which time he abolished the use of many useless and obsolete therapeutic treatments. In addition, he published a four-volume book on the importance of rational pharmacology in clinical science. After his retirement in 1923, he returned to an earlier interest: the history of medicine. During his career, Gram received several honors including the Danneborg Commander's Cross, the Golden Medal of Merit, and an honorary M.D. Gram died in Copenhagen, on November 14, 1938.