Mindblown: a blog about philosophy.
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Water bacteriology
The bacteriological standard of a water supply is indicated by its content of coll, the presence of which organism—harmless in itself—indicates faecal pollution. Other examinations for content of Cl. welchii and of faecal streptococci may be performed for the same reason. The total count of viable bacteria yields little information of value and is rarely…
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Wassermann reaction
Serological test for syphilis, one of the earliest and most used examples of the complement fixation test. Many modifications of the original test have been made and are variously employed; Price’s (Whitechapel) technique of 1949 -50 is a much-used UK method. The most commonly used test for the diagnosis of syphilis. A sample of the…
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Volutin granules
Granules in bacilli or yeasts, with an intense affinity for basic dyes (cf. lipid granules) and staining metachromatically with methylene or toluidine blue to give a red-violet colour contrasting with the blue of the bacillary protoplasm.
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Viskaps
Cellulose caps which, fitted wet and loosely over bottle tops, dry and shrink to produce a tight dustproof seal.
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Viruses
Infective agents of ultramiscroscopic size, filter-passing, intracellular, obligatorily parasitic, cultivable only on living cells as opposed to the classical inanimate culture media, and resistant to many antibiotics and chemical agents lethal to bacteria. Viruses are measured by their size in nanometres, vary from 10 to 450 nm, and consist of a core of nucleic acid…
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Virales
The viruses, one of the two orders within the class Microtatobiotes.
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Vi antigen
A surface somatic antigen of some enterobacterial species, especially S. typhi. Its occurrence in freshly isolated strains of this organism may nullify agglutination by ‘O’ and ‘H’ antisera. Boiling the suspension destroys the Vi coating, or the untreated suspension may be agglutinated by a Vi antiserum (prepared from alcohol-treated strains). Possession of the Vi antigen…
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Viable unit
The organism or organisms from which a bacteriological colony develops on culture. The enormous variations inherent in the numbers of organisms in such units are reflected in lack of reproducibility in viable count tests.
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Veillonella
Minute (0.3 Mm) anaerobic Gram-negative cocci occurring in masses. Commensals of the human mouth, alimentary tract etc., they may occasionally assume a pathogenic role. A genus of gram-negative, anaerobic diplococci that inhabit the oral cavity and gastrointestinal tract. Although Veillonella species rarely cause human disease, occasional episodes of bone or blood-borne infection have been reported.…
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Ultra-violet radiation
Total sterility is rarely achieved by ultra-violet radiation, the method being usually aimed at the reduction of bacterial population in air, water and on surfaces-particularly in sterile rooms and inoculation cabinets. The most effective wavelengths are 240-280 nm; the rays, emitted by mercury vapour lamps, possess little penetrating power but are readily transmissible in air…
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