gram-negative


Also found in: Dictionary, Thesaurus, Encyclopedia, Wikipedia.
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 ?
X-Biotix is a discovery, early preclinical-stage company that was spun out of X-Chem and incorporated in 2016, with a focus on delivering the next generation of antibiotics to combat multi-drug resistant Gram-negative pathogens.
Part of the problem has been that we don't really know what makes an antibiotic effective against Gram-negative bacteria.
In the same study, the rate of gram-negative bacteria was 5.
Caption: An old lab technique for differentiating bacteria as either gram-positive (left) or gram-negative (right) has been incorrectly explained for decades.
Appreciation of the affinity of gram-negative organisms for the toe-webs is important for selection of appropriate antibiotic therapy.
As a result of increasing antibiotic resistance to several types of gram-negative bacilli, the Centers for Disease Control and Prevention has also set up the Multi-Site Resistant Gram-Negative Bacilli Surveillance Initiative (MuGSI) to track infections due to carbapenem-resistant organisms including E.
A review of the Gram-Negative Bacterial Infections products under development by companies and universities/research institutes based on information derived from company and industry-specific sources.
Gram-negative bacteria that are highly resistant to existing treatments include E.
Klebsiella and other gram-negative bacteria are notorious for their ability to produce beta-lactamases, which are enzymes that render penicillin and some other antibiotics useless.
So Melander, Worthington and graduate students Cynthia Bunders and Catherine Reed set to work on a variety of the compound that might prove similarly effective against their Gram-negative brethren.
The drug would represent the first new class of antibacterial agent to treat Gram-negative infections in 30 years.
Objective: Extended spectrum ss-lactamases (ESBLs) represent a major group of lactamases currently being identified in large number worldwide mostly produced by gram-negative bacteria.