Gram-negative

[gram-neg-uh-tiv]

adjective

(often lowercase)

1. (of bacteria) not retaining the violet dye when stained by Gram's method.

Gram-negative

adjective

1. designating bacteria that fail to retain the violet stain in Gram's method

gram-negative

1. Relating to a group of bacteria that do not change color when subjected to the laboratory staining method known as Gram's method or Gram's stain. Gram-negative bacteria have relatively thin cell walls and are generally resistant to the effects of antibiotics or the actions of the body's immune cells. Gram-negative bacteria include E. coli and the bacteria that cause gonorrhea, typhoid fever, rickettsial fever, cholera, syphilis, plague, and Lyme disease.

2. Compare gram-positive

Word History and Origins

Origin of gram-negative¹

First recorded in 1905–10; Gram's method

Example Sentences

He will be targeting AI at a tricky group of infections, called Gram-negative bacteria, that includes well known bugs such as E. coli and Klebsiella pneumoniae.

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Treating carbapenem-resistant Gram-negative bacterial infections is doubly difficult because those bacteria are resistant to some of the most powerful antibiotics.

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Gram-negative bacteria have a double layer of protection, making them more difficult to kill, Muñoz said.

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Fusobacterium is a Gram-negative microbe found in the GI tract and the oral cavity, and previous studies have connected it to the development of CRC.

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A new medicine capable of combating Gram-negative bacteria, a particularly hardy type of bug with inner and outer membranes that antibiotics struggle to cross, hasn’t hit the market in 50 years.

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