Mindblown: a blog about philosophy.
-
Oxidase test
Primary characterization test appHcable particularly to Gram-negative bacteria, colonies turning intensely violet on contact with 1 per cent tetramethyl-p-phenylenediamine dihydrochloride. Neisseria and Pseudomonas are strongly positive, but other genera share the characteristic. In Kovac’s version of the test a platinum loop is used to mix colony with reagent on filter paper; reaction should occur within…
-
Orskov’s method
Observation of growing bacteria and their colony formation by repeated microscopical study of an inoculated square of agar incubated on a sterile slide under moist conditions. The method has been applied especially to the morphology of Actinomyces species.
-
Organotrophs
Those bacteria (the majority, and all parasitic species) which for growth and multiplication require complex sources of carbon and energy—such as carbohydrates, amino acids, peptides and lipids.
-
Optochin
Ethylhydrocupreine hydrochloride, used for the differentiation of true pneumococci (Streptococcus pneumoniae) from other alpha- haemolytic streptococci. Filter paper discs 5 -8 mm in diameter, impregnated with a 1/4000 solution, are placed on blood agar plates inoculated with the suspect strains. Only pneumococci are inhibited, a 5 -10 mm zone of inhibition surrounding the disc.
-
Nutrient gelatin
Medium for testing the proteolytic action of bacteria. Gelatin, 15 per cent, is added to nutrient broth, dissolved with heat, cleaned with white of egg and filtration, and sterilized. The medium sets at 24°C, unless permanently liquefied by the action of inoculated proteolytic organisms. A bacterial culture medium composed of broth and gelatin.
-
Nutrient broth
Stock bacteriological broth composed of meat extract base with added water, peptone and salt. The mixture is heated, filtered and sterilized.
-
Non-lactose-fermenters
Those enterobacteria which ferment lactose peptone-water irregularly, late, or not at all—Salmonella, Shigella, Arizona, Bethesda – Ballerup group, AIkalescens – Dispar group, Citrobacter, Proteus, Serratia and Hafnia genera.
-
Nocardia farcinica
Type-species of the Nocardia, a markedly acid-fast branching mycelial organism with grey-white to yellowish colonies. Associated with tuberculous-like processes in cattle. Non-acid-fast species, colonies white, buff or crimson, but chromogenicity is unpredictable. Actinomycosis-like pus is formed in the tissues. Associated with Madura foot (tropical and subtropical areas) but this condition is also as often fungal…
-
Nocardia asteroides
Species associated with brain abscess and with pulmonary tuberculosis-like disease. Fine mycelium, acid-fast, pigmentation yellow to red according to medium; easy of cultivation. First described by Eppinger in 1891. A species pathogenic for humans in which abscesses called mycetomas arise in the skin. The invasion site may be the lungs or skin.
-
Niacin test
Test of the ability of mycobacteria to produce nicotinic acid (niacin). Well grown cultures on solid media are treated with cyanogen bromide followed by aniline or o-tolidine; a yellow colour is produced if niacin is present. Only tuberculosis gives a positive result. Test papers avoid the dangers of the chemicals mentioned above.
Got any book recommendations?