Gram stain: The Danish bacteriologist J.M.C. Gram (1853-1938) devised a method of staining bacteria using a dye called crystal (gentian) violet. Gram’s method helps distinguish between different types of bacteria.

The gram-staining characteristics of bacteria are denoted as positive or negative, depending upon whether the bacteria take up and retain the crystal violet stain or not.

Gram-positive bacteria retain the color of the crystal violet stain in the Gram stain. This is characteristic of bacteria that have a cell wall composed of a thick layer of a particular substance (specifically, peptidologlycan containing teichoic and lipoteichoic acid complexed to the peptidoglycan).

The Gram-positive bacteria include staphylococci (”staph”), streptococci (”strep”), pneumococci, and the bacterium responsible for diphtheria (Cornynebacterium diphtheriae) and anthrax (Bacillus anthracis).

Gram-negative bacteria lose the crystal violet stain (and take the color of the red counterstain) in Gram’s method of staining. This is characteristic of bacteria that have a cell wall composed of a thin layer of a particular substance (specifically, peptidoglycan covered by an outer membrane of lipoprotein and lipopolysaccharide containing endotoxin).

The Gram-negative bacteria include most of the bacteria normally found in the gastrointestinal tract that can be responsible for disease as well as gonococci (venereal disease) and meningococci (bacterial meningitis). The organisms responsible for cholera and bubonic plague are Gram-negative.

MedTerms (TM) is the Medical Dictionary of MedicineNet.com.
We Bring Doctors’ Knowledge To You

Scientists doing groundbreaking research in the UK have suggested tadpoles may hold the key to developing new drugs to treat skin cancer. There is a study about it in the latest issue of the Cell Press journal Chemistry & Biology published on 30 January.

NICE’s contentious skin cancer guidance seems to be triggering a steep increase in hospital activity throughout the UK, according to an article published by Pulse. During the last nine months of 2008 GP dermatology referrals rose by 24% compared the same period in 2007 (figures gathered from 30 NHS acute trusts).

GPs say they are being frozen out of Lord Darzi’s rollout plan for the NHS, as well as being given little to say in vital decision that will shape the future of general practice, according to an article published this week in Pulse. Three senior GPs, all members of Darzi’s primary care advisory board, reveal that three times as many consultants are involved in implementing Darzi’s plans as GPs.

A new study from the US found that moderate weight reduction helped to reduce urinary incontinence among overweight and obese women. The research was the work of first author of Dr Leslee Subak from the University of California, San Francisco (UCSF), and colleagues, and is published online in the 29 January issue of the New England Journal of Medicine.

A small trial at a US hospital where patients with early stage MS had their own immune system stem cells transplanted back into their bodies appears to have reversed the neurological dysfunction of the early stages of the disease by causing their immune systems to “reset”. The scientists said the results should now be confirmed with a larger, randomized trial.

Urate: A salt derived from uric acid. When the
body cannot metabolize uric acid properly, urates can build
up in body tissues or crystallize within the joints.

See
also gout, uric acid.

MedTerms (TM) is the Medical Dictionary of MedicineNet.com.
We Bring Doctors’ Knowledge To You