gram-negative

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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 ?
Among them, predominant organisms were Gram-negative bacilli with Pseudomonas (18 isolates) being most common organism with the highest sensitivity to piperacillin + tazobactam, imipenem and amikacin.
Gram-negative bacilli as nontransient flora on the hands of hospital personnel.
We identified 11 species of bacteria from masked booby (Sula dactylatra) and Christmas shearwater (Puffinus nativitatis); 5 species of gram-negative bacilli, 4 species of Streptococcus (Enterococcus), and 2 species of Staphylococcus.
Thirty to fifty percent of endogenous endophthalmitis cases are caused by streptococci, while Staphylococcus aureus is responsible for 25% of cases and Gram-negative bacilli for 30% of cases (11-12).
Overall, Gram-negative bacilli, Gram-positive cocci and Candida spp.
Potassium tellurite, which inhibits other Gram-positive organisms, and lithium chloride, inhibitory to Gram-negative bacilli, provide the necessary selectivity.
An international group of specialists in infectious diseases discuss newly recognized diseases, previously known pathogens that present new challenges, and domestic and international threats, including the 2009 flu pandemic in Australia, the reemergence of human adenovirus 14, acanthanmoeba polyphaga mimivirus, the global impact of hepatitis E, human T-lymphotropic virus 1 in indigenous populations in Australia, cytomegalovirus infection in transplant recipients, HIV-associated malignancies, the global spread of multidrug-resistant gram-negative bacilli, sepsis in sub-Saharan Africa, neglected tropical diseases, infections in long-term care facilities and mobile populations, infectious plant diseases, and the One World-One Health initiative.
Aeromonas hydrophila is a motile gram-negative bacilli typically causing infection after exposure of wounds to fresh water, soil, or marine creatures, and oral consumption of contaminated food (1,2).

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