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.

acid-fast stain a staining procedure for demonstrating acid-fast microorganisms.

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

endogenous stain an intrinsic stain acquired during tooth development.

exogenous stain an intrinsic stain acquired after a tooth has erupted.

extrinsic stain a stain that can be removed from a tooth surface by polishing.

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. Stained elements appear pink to purple to blue.

Gram stain a staining procedure in which bacteria 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 called gram-positive, and those losing the stain but staining with the counterstain are called gram-negative.

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

intrinsic stain a stain that is within the enamel of a tooth and cannot be removed by polishing.

metachromatic stain one that produces in certain elements a color different from that of the stain itself.

nuclear stain one that selectively stains cell nuclei, generally a basic stain.

port-wine stain a persistent dark red to purple nevus flammeus that grows proportionately with the affected child and is usually found on the face. Initially it is macular, but the surface may develop angiomatous overgrowths with time. Port-wine stains often occur in association with other congenital abnormalities.

supravital stain a stain introduced in living tissue or cells that have been removed from the body.

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 phases of arteriography, and presumed to indicate neoplasm.

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

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

Gram stain

(gram),

a method for differential staining of bacteria; smears are fixed by flaming or methanol, stained in a solution of crystal violet, treated with iodine solution, rinsed, decolorized, and then counterstained with safranin O; gram-positive organisms stain purple-black and gram-negative organisms stain pink; useful in bacterial taxonomy and identification, and also in indicating fundamental differences in cell wall structure.

Gram stain

(grăm) also

Gram's stain

(grămz)

n.

A staining technique used to classify bacteria in which a bacterial specimen is first stained with crystal violet, then treated with an iodine solution, decolorized with alcohol, and counterstained with safranin. Because of differences in cell wall structure, gram-positive bacteria retain the violet stain whereas gram-negative bacteria do not. Also called Gram's method.

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

Gram stain

(gram stān)

A method for differential staining of bacteria; smears are fixed by flaming, stained in a solution of crystal violet, treated with iodine solution, rinsed, decolorized, and then counterstained with safranin O; gram-positive organisms stain purple-black, and gram-negative organisms stain pink. Useful in bacterial taxonomy and identification and for indicating fundamental differences in cell wall structure.

Gram stain

(gram)

[Hans C. J. Gram, Danish physician, 1853–1938]

GRAM STAIN: (Top) Gram-positive Staphylococcus aureus in a pus smear (orig. mag. ×500) (Bottom) Gram-negative Campylobacter jejuni bacilli (orig. mag. ×500)

GRAM STAIN: (Top) Gram-positive Staphylococcus aureus in a pus smear (orig. mag. ×500) (Bottom) Gram-negative Campylobacter jejuni bacilli (orig. mag. ×500)

A method of staining bacteria, which is important in their identification.

Procedure

A film on a slide is prepared, dried, and fixed with heat. The film is stained with crystal violet for 1 min; rinsed in water, then immersed in Gram's iodine solution for 1 min. The iodine solution is rinsed off and the slide decolorized in 95% ethyl alcohol. The slide is then counterstained with dilute carbolfuchsin or safranin for 30 sec, after which it is rinsed with water, blotted dry, and examined. Gram-positive bacteria retain the violet stain and gram-negative bacteria adopt the red counterstain. See: illustration

Note

As a simple means of checking on the accuracy of the staining materials, a small amount of material from between one's teeth can be placed on the slide at the opposite end from that of the specimen being examined. As gram-negative and gram-positive organisms are always present in the mouth, that end of the slide should be examined first. If both types of organisms are seen, the specimen may then be examined.

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,

Hans Christian Joachim, Danish bacteriologist, 1853-1938.

Gram iodine - a solution containing iodine and potassium iodide, used in Gram stain.

Gram stain - a method for differential staining of bacteria.

Weigert-Gram stain - see under Weigert

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

(gram stān)

Method for differential staining of bacteria; smears are fixed by flaming or methanol, stained in a solution of crystal violet, treated with iodine solution, rinsed, decolorized, and then counterstained with safranin O; gram-positive organisms stain purple-black and gram-negative organisms stain pink; useful in bacterial taxonomy and identification, and also in indicating fundamental differences in cell wall structure.