gram-negative


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Related to gram-negative: gram-positive, gram-negative folliculitis

gram-negative

 [gram-neg´ah-tiv]
losing the stain or decolorized by alcohol in Gram's method of staining; see Gram stain. This is a primary characteristic of bacteria having a cell wall composed of a thin layer of peptidoglycan covered by an outer membrane of lipoprotein and lipopolysaccharide.

gram-neg·a·tive

(gram-neg'ă-tiv), In this expression gram begins with lowercase g but Gram stain takes an uppercase G.
Refers to the inability of a type of bacterium to resist decolorization with alcohol after being treated with crystal violet. However, following decolorization, these bacteria can be readily counterstained with safranin, imparting a pink or red color to them when viewed by light microscopy. This reaction is usually an indication that the outer structure of the bacterium consists of a cytoplasmic (inner) membrane surrounded by a relatively thin peptidoglycan layer, which in turn is surrounded by an outer membrane. See: Gram stain.

gram-negative

/gram-neg·a·tive/ (-neg´ah-tiv) losing the stain or decolorized by alcohol in Gram's method of staining, characteristic of bacteria having a cell wall surface more complex in chemical composition than the gram-positive bacteria.

gram-negative

or

Gram-negative

(grăm′nĕg′ə-tĭv)
adj.
Of, relating to, or being a bacterium that does not retain the violet stain used in the Gram stain method.

gram-negative

Etymology: Hans C.J. Gram, Danish physician, 1853-1938; L, negare, to say no
having the pink color of the counterstain used in Gram's method of staining microorganisms. This property is a primary method of characterizing organisms in microbiology. Some of the most common gram-negative pathogenic bacteria are Bacteroides fragilis, Brucella abortus, Escherichia coli, Haemophilus influenzae, Klebsiella pneumoniae, Neisseria gonorrhoeae, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella typhi, Shigella dysenteriae, and Yersinia pestis.

gram-neg·a·tive

(gram-neg'ă-tiv)
Refers to the inability of a bacterium to resist decolorization with alcohol after being treated with Gram crystal violet. However, following decolorization, these bacteria can be readily counterstained with safranin, imparting a pink or red color to the bacterium when viewed by light microscopy.
See: Gram stain

Gram-negative

see GRAM'S STAIN.

Gram-negative

Refers to the property of many bacteria that causes them to not take up color with Gram's stain, a method which is used to identify bacteria. Gram-positive bacteria which take up the stain turn purple, while Gram-negative bacteria which do not take up the stain turn red.

gram-neg·a·tive

(gram-neg'ă-tiv)
Refers to the inability of a type of bacterium to resist decolorization with alcohol after being treated with crystal violet.

gram-negative,

n having the pink color of the counterstain used in Gram's method of staining microorganisms. Staining property is a common method of classifying bacteria. See also Gram's stain.

gram-negative

said of bacteria that are decolorized by alcohol in Gram's method of staining (see gram's stain), and are thus stained only with the counter stain (usually red). Gram-negative bacteria have a much thinner layer of peptidoglycan in the cell wall than Gram-positive bacteria.
References in periodicals archive ?
Caption: An old lab technique for differentiating bacteria as either gram-positive (left) or gram-negative (right) has been incorrectly explained for decades.
Ceftazidime-avibactam addresses important needs in the treatment of Gram-negative infections, including those caused by extended spectrum [eth]-lactamase-producing Gram-negative pathogens, carbapenem-resistant Enterobacteriaceae(CRE) and multidrug-resistant (MDR) Pseudomonas aeruginosa.
Appreciation of the affinity of gram-negative organisms for the toe-webs is important for selection of appropriate antibiotic therapy.
Works against Gram-negative bacteria at all phases of growth, including dormant cells that are prone to become resistant.
These drugs have the potential to address the immediate global need for antibiotics to overcome MDR infections, in particular those caused by PDR and XDR Gram-negative bacteria.
Once inside the cancer cells, the AMPs target and damage the cell's power plant, an organelle called the mitochondria, which has a double-layered membrane that is remarkably similar to that of Gram-negative bacteria," he said.
But ceftaroline was effective against a range of gram-positive and gram-negative organisms.
This is a serious concern, since enteric bacteria are responsible for more than 80% of all the hospital infections caused by Gram-negative bacteria.
In contrast to vancomycin, ceftobiprole has in vitro microbiological activity against a broad spectrum of Gram-positive and Gram-negative pathogens.
The case highlights the potential for multidrug-resistant gram-negative organisms to occur outside their previously recognized settings in large metropolitan centers.
There's not a lot of information in the literature about controlling gram-negative pathogens.
Cat-scratch disease was first reported by Debre et al in 1950, (5) but its etiology was not known until Wear et al, (6) using the Warthin-Starry stain, identified a gram-negative bacillus in the lymph nodes of affected individuals in the 1980s.