Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving viable micro-organism
Patent
1996-01-31
1998-04-14
Leary, Louise
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving viable micro-organism
4352871, 4352831, 435968, 435 34, 435 4, 435805, 436808, 396511, 422 55, 422 681, 422 8205, 430945, C12Q 102, C12Q 100, A01N 102, G01N 3353
Patent
active
057390037
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for determination of numbers of microorganisms present in materials and for predicting their growth capability in these, analogous materials such as foodstuffs, in growth media and in the presence of chemical agents. Further provided are immobilizing cassettes and optical apparatus for use in this method.
Many methods can be used for determination of the rate of bacterial growth. These can involve direct measurement of the number of viable bacteria by plating techniques, measurement of the intensity of scattered light, absorption of light or some indirect measurement of cell concentration such as ATP and bioluminescence, or electroimpedence measurement. Few of these techniques are amenable to continuous monitoring and hence they require repetitive sampling, which is often laborious and time consuming, and others are relatively insensitive and require the presence of large numbers of bacteria.
Traditional approaches to the problem of food safety have involved inoculation of a material under investigation with a suspension of a known bacterial species and measuring the number of viable cells during storage; this being known as challenge testing. Such a method gives data that is applicable only to the foodstuff actually tested. For predictive purposes relating to untested foods it is necessary to investigate factors that contribute to the growth or death of bacteria under predetermined analogous conditions to that foodstuff. Similarly, the pharmaceutical and laboratory chemicals industry has an ongoing need for methods which can select media and agents for their ability to selectively promote, support or inhibit microbial growth, or on the basis of their microbicidal activity. Drugs, e.g. antibiotics, must be screened for activity against particular microorganisms and the concentration required for achieving that effect must be determined.
It is known to use the ability of a material to scatter laser light for the purpose of studying biological materials such as proteins, cells, viruses and tissue fragments (see e.g. EP 0514178, WO 88/01736, U.S. Pat. No. 5,155,549 and U.S. Pat. No. 4,764,013) in a detection zone in a conduit. It is further known to use such ability for measuring antibody-antigen responses in a scattering cell (see e.g. EP 0064230, U.S. Pat. No. 4,799,796) and for characterising microparticles, including bacteria, and their use in indicating the presence of various agents (see e.g. EP 0102726). The known systems use sample or flow cells to contain the material under study but do not allow the study of microorganism growth in a large number of samples under a variety of conditions, nor do they address the problems of reproducibility results from such testing.
The present inventors have now provided a novel method capable of rapidly determining the presence and numbers of microorganisms in test media, and thus of predicting the growth rate of such microorganisms in these and in analogous materials. They have also provided culture immobilizing cassettes and optical apparatus which allow the rapid screening of such materials in a collocated format using the method whereby the amount of predictive data that can be generated in one step is increased. The method and apparatus particularly facilitate prediction of microbial growth in media of complex physicochemical microstructure.
Where a material, e.g. a foodstuff, has homogeneous pH, salt and/or nutrient concentration, prediction of growth of given microorganisms in it may be carried out using modelling techniques based upon results from analogous growth media studies. Such models however are not well suited to the study of materials having complex microstructure such as those containing dispersed particulates, air bubbles, liquid droplets or solid particles; many of these often occurring in a liquid continuous phase in foodstuffs. In such cases a variety of conditions require study in a statistically valid fashion.
The present invention provides a technique wherein, in a preferred predictive format, micro
REFERENCES:
patent: 3990851 (1976-11-01), Gross et al.
patent: 4541719 (1985-09-01), Wyatt
patent: 4972258 (1990-11-01), Wolf et al.
patent: 5366858 (1994-11-01), Koizumi et al.
Brocklehurst Timothy F.
Mackie Alan R.
Steer David C.
Wilson David R.
Leary Louise
The Minister of Agriculture Fisheries and Food in her Britannic
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