Category: R

Type of natural immunity shared by members of a race.  

Discrete colonies on a plate culture are derived by touching the charged loop on the outer edge of a plate of medium revolving on a mechanical turn-table, then drawing the loop slowly to the centre, resulting in a spiral of diminishing inoculum.  

Yeast extract – peptone – lactose medium for the first culture of bacteria (especially enterobacteria) attenuated by membrane filtration or other treatment, and which may fail to grow if first cultivated on differential media.  

Bacteria dormant by reason of sporulation or microcystic formation. A cell not in the process of dividing.  

Expression of the result of mycobacterial sensitivity tests by reference to a parallel series of readings provided by either the control strain tuberculosis hominis H.37 Rv or by the modal resistance of a number of sensitive wild strains. Patient strains with an MIC 8 times that of the control are styled ‘very resistant’; of 4…

Test for bacteriological quality of milk analogous to the methylene blue test, but using resazurin, a dye which passes through successive colour changes from its original blue, through mauves and pinks to colourless. This allows quicker reading of results than the 30 minutes of the methylene blue test, and the resazurin test is used as…

Method for demonstrating whether the zones of inhibition around antibiotic discs on a plate culture represent bacteriostatic or bactericidal action. A sterile velour-faced wood stamp is pressed over the plate, and the impression transferred to a second uninoculated plate of similar medium. Growth of micro-organisms within area corresponding to the zones of inhibition on the…

Meat extract – yeast extract – dextrose broth with the inclusion of cysteine hydrochloride, prepared as either solid or semi-solid by appropriate agar addition. Used particularly for the cultivation of Clostridia from small inocula (for example, in food and water bacteriology) but suited to the culture of other bacteria.  

Means of encouraging the growth of microaerophiles. Cultures are placed in a biscuit or similar tin, or anaerobic jar, together with a burning night-light. The light is extinguished as oxygen is reduced.  

Buffered tryptone broth with magnesium chloride and malachite green, for the selective cultivation of Salmonella from foodstuffs.