Gram stain procedure

Gram-Negative Refers to the inability of many bacteria to retain crystal violet or similar stain through the standard Gram stain procedure. They show only the red counter-strain. 

The thickness and chemical composition of the cell wall and its adjacent structures determine how avidly a cell wall takes up and/or retains specific dyes. Most cells can be differentiated on the basis of whether they retain crystal violet stain during the Gram stain procedure. Those that can retain the dye, called Gram positive, do so because their cell walls consist of a thick peptidoglycan layer. In contrast, Gram-negative cells possess a thin peptidoglycan layer. Often... 

Bacteria can be broadly classified into two groups the gram-positive bacteria, which are stained purple after the gram staining procedure, and the gram-negative bacteria, which are stained red. The difference in staining reflects differences in the structure of the cell... 

Gram positive Bacterial cells which retain the crystal violet stain during a staining procedure. Most strains of bacilli are gram positive. 

Gram Stain A staining procedure used in classifying bacteria. A bacterial smear on a slide is stained with a purple basic triphenyl methane dye, usually crystal violet, in the presence of iodine/potassium iodide. The cells are then rinsed with alcohol or other solvent, and then counter-stained, usually with safranin. The bacteria then appear purple or red according to their ability to keep the purple stain when rinsed with alcohol. This property is related to the composition of the bacterial cell wall. 

Direct examination of tissue or body fluids believed to be infected can provide simple, rapid information to the clinician. Microscopic examination of wet-mount specimen preparations can provide valuable information regarding potential pathogens. Applications of this procedure with or without staining preparations include direct examination of sputum, bronchial aspirates, scrapings of mucosal lesions, and urinary sediment. The Gram stain is one of the... 

One of the most commonly used procedures, the Gram stain, differentiates bacteria based upon cell wall characteristics. The procedure calls for initial... 

Supplemental Notes. Most suppliers of scientific equipment and supplies market prepackaged Gram stain kits (sufficient to do hundreds of Gram stains) at nominal prices (approx 30). It is recommended that interested parties purchase these and follow the instructions provided with the kit. Aside from procedural matters relative to staining, several additional issues merit consideration. 

As seen in Table 2-1, acetic acid bacteria are separated from LAB by both Gram stain and catalase activity. Although generally indicative of aerobic organisms (see discussion in Procedure 2.3.2), catalase activity among some strains of Acetobacter is variable and occasionally difficult to demonstrate. 

The rational and procedural details for Gram staining are presented in Chapter 1 (Procedure 1.5.1). 

The Gram stain in its many modifications is one of the most widely used bacteriological procedures. Even the most earnest advocates of Adansonian theory view the Gram stain with some special emphasis. Soon after its initial use by... 

In Table 1 a summary of the procedure followed by the present author is presented. Its essential element is that it starts with a quantitative microscopic examination of a Gram-stained preparation of a tenfold dilution of the food. This is often referred to in the European literature as bacterioscopic examination As can be seen from Table 1, this procedure as a rule provides a most useful indication of the possible aetiology within about 15 minutes of the... 

Not all bacteria can be stained by the Gram procedure, however, and these often require special staining processes for visualization. Among the more prominent of these for our purposes are the mycobacteria (the causative agents of tuberculosis, for example). These very waxy cells are called acid-fast and are stained by carbol fuchsin instead. 

Stain Technique No. 1 (Feldspars, Quartz, and Calcite). Chemicals needed in this procedure are concentrated HF (52%), a 5% barium chloride solution in distilled water, a saturated solution of sodium cobaltinitrite, and a solution of amaranth (28 grams of F.D. and C. Red No. 2 pure coal tar dye in 2 liters of water). Amaranth is also called Azorubin S, C. 1.16185, available from Polysciences, Inc., in Warrington, Pennsylvania, and other chemical supply houses. This stain is primarily for silicates, but may include clay minerals when aggregated in shale particles. Testing with the shale, as such, will define the usefulness of the stain in this regard. 

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