Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving viable micro-organism
Patent
1996-01-26
1998-02-10
Kight, John
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving viable micro-organism
435 29, C12Q 104
Patent
active
057167990
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for demonstrating the presence or absence of a particular strain of microorganism in a culture medium. the food industry, in relation to water monitoring or in medicine, in view of the fact that these microorganisms may not only prove to be pathogenic agents, but can also consist of agents that reveal some types of contamination.
Various methods enable the presence of microorganisms in a medium of some kind to be demonstrated, consisting in taking a sample of the medium in question and then in promoting the growth of the microorganisms present by culture on or in a suitable medium.
In order to simplify the demonstration of the microorganisms present, the use has been proposed, in the detection medium, of colored compounds whose presence is characteristic of a given microorganism.
The coloration often reveals an enzyme activity associated with the microorganism in question, and the outcome of this activity may result in a modification of the pH of the medium, revealed by a colored indicator (EP-A-0 395 532), or alternatively in the liberation of a chromophoric or fluorophoric compound (FR-A-2-684,110).
Chromophores or fluorophores are compounds generally obtained by enzymatic hydrolysis of corresponding chromogenic or fluorogenic compounds present in the culture medium.
Fluorophores emit a characteristic radiation by fluorescence.
Chromophoric compounds are characterized by a color with a dominant wavelength.
Among known chromophoric compounds, indoxyl derivatives, hydroquinoline derivatives, may be noted in particular.
In order to differentiate two different genera of microorganisms in a culture medium, the proposal has even been made to introduce two chromogenic agents each liberating a chromophoric compound with a color characteristic of the presence of a particular microorganism (U.S. Pat. No. 5,210,022).
Although all of these media are efficacious in detecting microorganisms of a specific genus, such as, for example, Salmonella, Candida or E. coli, and distinguishing them from other species, they do not, however, permit the detection of a large number of microorganisms of different genera on the same culture medium, or the differentiation of pathogenic species from others among microorganisms of the same genus.
Such a distinction appears to be all the more important for certain species of yeasts, such as Candida albicans which is responsible for more than 50% of pathologies associated with yeasts.
In point of fact, it was unexpectedly found that these drawbacks could be remedied by introducing into the culture medium at least one chromogen which is a substrate for an enzyme of the strain and at least one compound chosen from a carbohydrate at high concentration, so as to obtain a derived color different from the basic color of the chromophore.
Derived color is understood to mean any color whose dominant wavelength differs from the dominant wavelength of the chromophores liberated by the chromogens present in the culture medium, taken separately in a standard medium.
Standard medium is understood to mean any ordinary identification medium in which the carbohydrate has a simple function of carbon source, at very low or even zero concentrations, where it is considered that such concentrations make it possible to avoid any inducing effect which would modify the behavior of the microorganisms in an uncontrolled manner and would induce errors in the identification of the microorganisms in question.
The dominant wavelength of the chromophore may be calculated by reference to daylight, as defined by the CIE (International Commission on Energy color of an object, especially with a spectrocolorimeter.
Hence the present invention relates to a method for demonstrating the presence or absence of a particular strain of microorganism in a medium, characterized in that at least one chromogen which is a substrate for an enzyme of the strain and at least one compound chosen from a carbohydrate at high concentration are introduced into the culture medium, so as to obtain after hy
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Jones Dameron
Kight John
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