Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving viable micro-organism
Patent
1997-02-28
1998-09-15
Leary, Louise N.
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving viable micro-organism
435 4, 4353001, 435807, 4352831, 4352871, 4352875, 4352866, 4352852, 422 50, 422 83, 422 88, C12Q 104, C12Q 100, G01N 700, G01N 3096
Patent
active
058077014
DESCRIPTION:
BRIEF SUMMARY
This invention relates to detecting bacteria.
Bacteria are identified in a variety of ways. Many have characteristic forms which can be seen under microscopic examination, but some are identified, when colonised on a growth medium, by a characteristic colour and in some cases this is confirmed by smell. Not all bacteria have any appreciable odour, but many have a characteristic associated gas or vapour due to their inherent metabolic activities.
Patent Abstracts of Japan, application number JP-A-60130398, discloses a detector for detecting the presence of microorganisms on the basis of evolved gases. WO 94/04705 discloses a method of detecting E. Coli by monitoring a gaseous product, this gaseous product being produced by cleavage of a glucuronide conjugate by .beta.-glucuronidase produced by a certain bacterial species. GB-A-2176901 describes gas sensors based on the use of semi-conducting organic polymers, whilst U.S. Pat. No. 4,456,380 discloses an optical bacteria identification system using a plurality of optical filters.
The invention comprises a method for identifying bacteria comprising detecting gas or vapour associated with the metabolic activity of the bacteria and differentiating such gas or vapour from gas or vapour associated with other bacteria.
The method may comprise abstracting gas or vapour from a detection region and flowing the same over an array of sensors of which an electrical property varies according to exposure to gases or vapours and observing the response of the sensors.
The sensors may comprise semi-conducting polymers the resistance or impedance of which varies according to exposure to gases or vapours.
The response of the sensors may be compared against a library of responses to known bacteria, or the response may be input to a neural net trained against known bacteria.
The detection region may comprise an enclosed space above a Petri dish or like laboratory culture dish.
The array of sensors may first be purged using a purging gas.
The invention also comprises apparatus for detecting bacteria comprising detector means for detecting a gas or vapour associated with the bacteria.
Said detector means may comprise an array of sensors of which an electrical property varies according to exposure to gases or vapours. The sensors may comprise semi-conducting polymers the resistance or impedance of which varies according to exposure to gases or vapours.
The apparatus may comprise a store for a library of responses to known bacteria and comparison means operable automatically to compare a given response against the library. The apparatus may also comprise a neural net the input to which comprises the array of sensors and which is trained against known bacteria.
The apparatus may comprise a probe for sampling a detection region by abstracting gas or vapour from said region to be passed to said detector means. Said probe may comprise a cover for enclosing a Petri or like laboratory culture dish or an area of growth medium thereon.
Said probe may comprise a carrier gas feed and return and the apparatus may comprise a source of carrier gas.
Embodiments of apparatus and methods for detecting bacteria according to the invention will now be described with reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic illustration of a first embodiment;
FIG. 2 is a diagrammatic illustration of a second embodiment;
FIG. 3 is a diagrammatic illustration of an arrangement for detecting bacteria on a culture dish;
FIG. 4 is a diagrammatic illustration of an arrangement for detecting bacteria in a nutrient broth; and
FIG. 5 is a cluster analysis of vapour associated with three species of bacteria.
The drawings illustrate methods and apparatus for detecting bacteria comprising detecting gas or vapour associated with the bacteria, and, further, methods for identifying bacteria by differentiating such gas or vapour from gas or vapour associated with other bacteria.
FIGS. 3 and 4 illustrate abstracting gas or vapour from a detection region 11 and flowing the same over an array 12 of sensor
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Shen-Wu Ho, "Head-Space Gas-Liquid Chromatrographic Analysis for Presumptive Identification of Bacteria in Blood Cultures", Feb. 1986, pp. 18-26.
Gardner et al., "A brief history of electronic noses" Sensors and Actuators B. 18-19 (1994), pp. 211-220 Month not available.
J.L. Berdague et al., "Revue Caracterisation Instrumentale De La Qualite Des Matieres Premieres Et Des Aliments Par Analyse Des Composes Volatils", Viandes Prod. Carnes vol. 14, Sep.-Oct. 1993, pp. 135-138; (with English language summary).
M. Sasser, "Identification of Bacteria by Gas Chromatography of Cellular Fatty Acids", Technical Note #101, MIDI, May 1990, pp. 163-169.
M. Sasser, "`Tracking` a Strain Using the Microbial Identification System", Technical Note #102, MIDI, May 1990, pp. 171-174.
Payne Peter Alfred
Persaud Krishna Chandra
Aromascan PLC
Leary Louise N.
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