gram stain

stain (stān)

1. a substance used to impart color to tissues or cells, to facilitate microscopic study and identification.

2. an area of discoloration of the skin.

---

differential stain  one which facilitates differentiation of various elements in a specimen.

Giemsa stain  a solution containing azure II-eosin, azure II, glycerin, and methanol; used for staining protozoan parasites, such as Plasmodium and Trypanosoma, for Chlamydia, for differential staining of blood smears, and for viral inclusion bodies.

Gram stain  a staining procedure in which microorganisms are stained with crystal violet, treated with strong iodine solution, decolorized with ethanol or ethanol-acetone, and counterstained with a contrasting dye; those retaining the stain are gram-positive, and those losing the stain but staining with the counterstain are gram-negative.

hematoxylin-eosin stain  a mixture of hematoxylin in distilled water and aqueous eosin solution, employed universally for routine tissue examination.

metachromatic stain  one which produces in certain elements colors different from that of the stain itself.

port-wine stain  see nevus flammeus.

supravital stain  a stain introduced in living tissue that has been removed from the body, but before cessation of the chemical life of the cells.

tumor stain  an area of increased density in a radiograph, due to collection of contrast material in distorted and abnormal vessels, prominent in the capillary and venous phase of arteriography, and presumed to indicate neoplasm.

vital stain  a stain introduced into the living organism, and taken up selectively by various tissues or cellular elements.

Wright's stain  a mixture of eosin and methylene blue, used for demonstrating blood cells and malarial parasites.

---

Gram stain

Microscopic examination of a portion of a bacterial colony or sample from an infection site after it has been stained by special stains. Certain bacteria pick up and retain the purple stain; these bacteria are called gram-positive. Other bacteria loose the purple stain and retain the red stain; these bacteria are called gram-negative. The color of the bacteria, in addition to their size and shape, provide clues as to the identity of the bacteria.

Mentioned in: Gangrene, Sexually Transmitted Diseases Cultures, Sputum Culture

---

Gram stain

A procedure for detecting and identifying bacteria and certain other microbes. Microorganisms, such as those found in corneal or conjunctival samples, are stained with crystal violet, rinsed in water, treated with iodine solution, decolorized with ethyl alcohol or acetone and counterstained with a contrasting dye, usually safranin, a pink dye. The preparation is then rinsed with water, dried and examined. Microorganisms that retain the crystal violet stain are said to be Gram-positive, while those that retain the counterstain are said to be Gram-negative. Common Gram-negative bacteria include Acinetobacter, Chlamydia trachomatis, Enterobacter, Escherichia coli, Haemophilus influenzae, Moraxella lacunata, Neisseria gonorrhoeae, Proteus vulgaris, Pseudomonas aeruginosa. Common gram-positive bacteria include Mycobacterium chelonae, Mycobacterium fortuitum, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Streptococcus pyogenes. See bacteria.

---

gram stain

Bacteriology A stain formulated by a great Dane, HCJ Gram, for identifying broad groups of bacteria; GS may be performed on specimens from skin, tissue, urethral discharge–for N gonorrhoeae, endocervix, joint fluid, pericardial or pleural fluid, sputum, stool