WO1987007911A1

WO1987007911A1 - Sampling of material

Info

Publication number: WO1987007911A1
Application number: PCT/GB1987/000436
Authority: WO
Inventors: William J. Martin
Original assignee: The University Of Manchester Institute Of Science
Priority date: 1986-06-20
Filing date: 1987-06-22
Publication date: 1987-12-30

Abstract

A method of sampling material, particularly microbiological material, comprises deforming a resiliently deformable sampling area (5) for example by means of a plunger (6) so that the sampling area contacts the material to be sampled. The area is then allowed to return to its original condition. The sampling areas may be provided on an elongate strip which is indexed so as to bring successive sampling areas to the sampling position at which the deformation is effected. Alternatively, it is possible to provide a vessel with a number of compartments each of which has a resiliently deformable sampling area at its base. By deforming the sampling area from externally of the vessel, the area extends into the compartment and may contact a sample position near the mouth of the compartment. On returning the sampling area to its original condition, the sample is located within the compartment.

Description

SAMPLING OF MATERIAL

The present invention relates to the sampling of material, particularly but not exclusively microbiological material.

Plating out and culture inoculation is a procedure used extensively in life science laboratories. For example, the technique finds wide application in clinical biology as a means of disease identification and treatment, in molecular biology as part of the Sanger DNA sequencing protocol and in pharmaceutical research to screen antibiotics. Briefly, the method comprises growing microbiological material in, for example, a Petri-dish and then selecting from the resultant growth (or lawnj those colonies or plaques (e.g. of yeasts, fungi, bacteria or virus infected plaques) which are required for further study or amplification. The technique is currently effected manually by experienced personnel who, identify the colonies or plaques of interest, then 'pick-out' these colonies or plaques with individual sampling probes (usually sterile pointed sticks). The colonies or plaques are then transferred individually to discrete culture tubes or containers in which they are incubated prior to further processing. Many laboratories require hundreds, and possibly thousands, of such operations to be effected daily in a process which is manpower intensive, tedious, repetitive and error prone. Additionally, many cultures of interest may be ^•harmful and consequently there is a health risk with the transfer of such cultures. Furthermore, human operators carry a wide variety of organisms and it is, therefore, difficult to maintain sterile operating conditions when the procedure is being carried out manually.

According to the present invention there is provided a method of obtaining a sample of material, for example a colony or plaque of microbiological material, comprising positioning the material to be sampled proximate to a resilient sampling area, deforming the sampling area so that the area contacts the material, and allowing the area to resile away from the sample. The method is particularly useful for the sampling of microbiological material, e.g. colonies or plaques from a microbiological growth culture.

In one embodiment of the invention the method for obtaining a sample of a colony or plaque from a microbiological growth culture the method comprises ^"advancing an elongate sampling strip having a plurality of resiliently deformable sampling areas along a path which successively brings said areas to a sampling position, deforming the area at the sampling position so that said area contacts the colony or plaque to be sampled, allowing the area to return to its original condition, and continuing the advance of the strip to bring a successive sampling area to the sampling position.

For preferance, the elongate sampling strip will comprise a carrier strip having a plurality of successive apertures in which the resiliently deformable sampling areas are provided. Most preferably the carrier strip will be of a flexible plastics material which allows the sampling strip to be fed from a roll thereof (e.g. stored in a cassette). The sampling strip may be destroyed (e.g. by incineration) once the samples on the sampling areas have been collected- for further study. Alternatively the sampling strip may be sterilised for re-use.

Preferably the processing of the samples is effected at a transfer position to which the sampling areas are advanced from the sampling position. At the transfer position, the samples may, for example, be transferred to culture tubes or other containers for further growth.

Preferably also the areas carrying the samples are isolated from each other during their passage between the sampling and transfer positions. This may be achieved by an isolating strip which is advanced adjacent with the sampling strip between the sampling and transfer positions.

A further embodiment of the invention utilises a container for collecting samples of microbiological material,- ^' the container comprising at least one compartment having at its base a resilient sampling area which is deformable into the compartment.

The method of sampling microbiological material using such a vessel comprises positioning the material to be sampled proximate the top of a compartment, deforming the resilient sampling area of that compartment so as to contact and sample the material, and returning the sampling area to its original condition.

The vessel preferably comprises a plurality of compartments each with a respective resilient sampling area. This vessel may be used to sample, for example, different colonies or plaques from a growth (or lawn) of microbiological material. Each such sampled colony or plaque is thus located on the sampling area in a respective one of said compartments and is isolated from the samples in the other compartments. Nutrient liquid or the like may then be introduced into the individual compartments and the sample cultivated in the usual way.

This embodiment of the invention has the advantage that the individual samples of microbiological material are introduced directly into separate compartments so that no further measures need to be taken to avoid cross-contamination. Secondly, the samples may be cultured in the compartments so that there is no requirement for a further transfer operation.

The method of the invention lends itself readily to automation and may be incorporated into a fully automatic sampling system. Such a system may comprise (in addition to the sampling strip (or container) and a plunger or the like for effecting deformation of the resilient sampling areas) automatic visual recognition ^'means for identifying colonies of interest and." locating their position in the growth culture. Information from the visual recognition means is then used to control positional movement of the growth culture so that the colony or plaque of interest is beneath the plunger. Alternatively the growth culture may remain stationary and the plunger and sampling area may be positioned above the colony of interest, by movement of the sampling strip and plunger in the horizontal plane. The sampling strip and plunger may be incorporated in a mechanical handling robot which effects the sampling procedure. Using such a system a plurality of colonies from each of successive growth cultures supplied to the system may be rapidly sampled and transferred for culture inoculation or other processing.

The invention will be further described, by way of example only, with reference to the accompanying drawings; in which: Figs-. l(a)-(c) schematically illustrate a sampling strip and its use in the method of the invention;

Fig. 2 illustrates an implementation of the method of the invention;

Fig. 3 is an exploded perspective view of one embodiment of container in accordance with the invention, and

Figs. 4a-4e diagrammatically illustrate the use of the container shown in Fig. 3.

The sampling strip 1 shown in the plan view of Fig. la is of indefinite length and comprises a rubber latex membrane 2 sandwiched between two flexible, inelastic strips 3 (see sectional view of Fig. lb) . Spaced at _^intervals along each of strips 3 are identical apertures 4 positioned such that the apertures of the two strips 3 are in register. It will thus be seen that the sampling strip 1 has a plurality of successive 'exposed' sampling areas 5 of the rubber latex 2.

A reciprocable poined plunger 6 is positioned above strip 1 and the culture to be sampled is in a Petri-dish 7 (see Fig. lc).

To effect sampling, strip 1 is indexed forward in the direction of arrow A such that one of the sampling areas 5 is beneath plunger 6.

Plunger 6 is now moved downwardly such that its tip deforms the area 5 causing to project beyond the lower strip 3 and to come into contact with a colony to be sampled. Plunger 6 is then moved upwardly to its original position thus allowing the area 5 (now with a collected sample 8) to resile to its original form.

Strip 1 is now advanced so that the next area 5 is above a further colony to be sampled and the above procedure is repeated.

In order to insolate the collected samples 8 from each other (and therefore avoid cross-contamination) a flat cover (or isolation) strip 9 may be advanced in juxtaposition with the strip 1 (see Fig. lc).

Referring now to the arrangement shown in Fig. 2 (in which the reference numerals which are common to Figs. 1 and 2 denote like parts), the strip 1 is advanced in the direction of arrow A from a supply (not shown) successively through sampling and transfer stations and then to waste or a sterilisation area. The strip 1 may, for example, be moved by sprocket wheels engaging in perforations in the strip edge or by friction drive.

At the sampling station is the plunger 6 which is reciprocal within a hollow guide 10 around the lower end of which the strip 1 travels in the form of a ϋ. A similar arrangement of plunger 6' and guide 10' is provided at the transfer station.

During use of the apparatus the strip 3 is moved in increments (by means not shown) so that the areas 5 stop in succession below the pointed plunger 6 at the sampling station.

Additionally, the petri-dish 7 is so moved relative to plunger 6 or vice versa that each successive area 5 is directly above a colony of interest. Downward movement of plunger 6 causes its tip to deform the area 5 and sample the colony (as described with reference to Fig. 1). Plunger 6 is then returned to its upper position and the strip 1 is advanced. Area 5 carrying the sample 8 therefore moves towards the transfer station and a fresh area 5 is located below plunger 6 so that the procedure may be repeated. At the transfer station the sample 8 may be transferred to a culture container 11 by downward movement of plunger 6'. Preferably the culture container does not contain a fluid otherwise this fluid may be carried over after the inoculation process and cause contamination to other containers.

In order to prevent cross-contamination between samples 8 on areas 5 during their passage between the sampling and transfer stations, a disposable isolation strip 9 is fed in the direction of arrow B from a supply (not shown) to disposal means (not shown) or sterilisation means (not shown).

Means may be provided to allow storage or lengths of the strip 1 between the sampling and transfer- stations₄ in a buffer system to allow for differences between sampling and transfer rates. The strip may also be stored in a. cassette between sampling and transfer.

The embodiment illustrated in Figs. 1 and 2 has a number of advantages. In particular the plunger 6 may be accurately positioned by mechanical means so that the method allows sampling of culture areas onto the sampling strip with good positional resolution. Additionally, the planar nature of the sampling strip, except at the moment of sampling, allows easy storage thereof is a roll in a cassette or the like. Similarly, the isolation strip is also of simpler shape than that shown in our earlier application and may therefore be stored more easily in roll form. Furthermore the planar sampling and isolation strips are of comparatively low cost.

The container 101 shown in Fig. 3 is of open-topped form (the container being illustrated in an inverted position) and comprises a plurality of compartments 102 as defined by the intersecting walls 103 and 104 within the container. The box of the container is of a laminate type structure comprised of two base members 105 and 106 with registering apertures 107 (only some of which are shown for base member 106). A layer of elastomeric material 108 is sandwiched between base members 105 and 106 so that portions of this material 108 are exposed from both outside and within the container through apertures 107.

Although Fig. 3 illustrates an exploded perspective view of the container it will be appreciated that the various components of * the laminated base construction are secured together by any suitable means (e.g. by adhesive).

The use of the container 101 • is illustrated in Figs. ^*4a-4e. The container 101 is in its inverted position and is located over a culture container 109 from which a colony is to be sampled. More specifically, container 101 is moved relative to culture 109 so that a compartment 102 is located over the colony to be sampled. A plunger 10 is moved downwardly from externally of the container so as to locate through an aperture 107 and progressively deform the exposed area of the elastomeric material 108 and expand it into compartment 102. Downward movement of plunger 110 is continued until the material 108 contacts a colony to be sampled (Fig. 5c) at which point plunger 110 is withdrawn so as to allow material 108 to return to its non-deformed condition (Fig. 4e). As shown in Fig. 4e a colony 111 of the culture has been collected on material 108.

The above procedure is ^' of course repeated so that colonies of interest may be located in each of the compartments 102.

Finally, the container 1 may be inverted from the position shown in Fig. 4 and the compartments 102 filled with culture medium as desired. Culture of the samples may then take place under standard conditions.

The illustrated container is square and comprises a matrix of compartments but it will be appreciated that a number of modifications may be made. In particular, it is possible to provide a container which comprises only a single row of compartments as such a container may be more suitable for particular applications.

The illustrated embodiments of the invention may be incorporated in a robotic sampling system in which each culture container is scanned by a vision system which is such that the position and characteristic (such as colour, shape, size and transparency) of individual colonies in the culture are imaged and recorded. This may be achieved by using a vision system sensitive to small colour and location changes in a poor contrast environment. For example, a high resolution CCD matrix or line camera linked to a computer may be employed with background illumination. Intelligent pattern recognition software will be used for characterisation, classification, co-ordinate computation and generation of overall culture statistics.

The exact position of colonies of interest may thus be determined and this information is used to control the exact position of culture containers on the X-Y axis in relation to the tip of plunger so that plunger may be moved downwards to sample the colony of interest in the manner previously described. Alternatively the plunger may be positioned on the X-Y axis so that its tip is vertically above a colony of interest.

Claims

CLAIMS ;

1. A method of obtaining a sample of material, for example a colony or plaque of microbiological material, comprising positioning the material to be sampled proximate to a resilient sampling area, deforming the sampling area so that the area contacts the material, and allowing the area to resile away from the sample.

2. A method as claimed in claim 1 comprising advancing an elongate sampling strip having a plurality of resiliently deformable sampling areas along a path which successively brings said areas to a sampling position, deforming the area at the sampling position so that said area contacts the colony or plaque to be sampled, _^allowing the area to return to its original condition, and continuing the advance of the strip to bring a successive sampling area to the sampling position.

3. A method as claimed in claim 2 wherein the elongate sampling strip comprises a carrier strip with a plurality of successive apertures in which the resiliently deformable sampling areas are provided.

4. A method as claimed in claim 3 wherein the sampling strip is fed from a roll thereof.

5. A method as claimed in claim 2 wherein the resilient areas carrying the samples are advanced to a transfer position at which the samples are transferred from the strip.

6. A method as claimed in claim 5 wherein the samples are isolated from each other during travel of the strip between the sampling and transfer positions.

7. A method as claimed in claim 1 in which the resilient sampling area is at the base of a container, the method comprising positioning the material to be sampled proximate the mouth of the container, effecting the resilient deformation of the sampling area, into the container so that the are contacts and samples the material, and returning the sampling area to its original.

8. A method as claimed in claim 7 wherein the container comprises a plurality of compartments each with a sampling area resiliently deformable into the compartment.

9. A method as claimed in any one of claims 1 to 8 wherein the material to be sampled is a microbiological material.

10. A sampling strip comprising a plurality of longitudinally spaced apertures in which resiliently deformable sampling areas are provided.

11. A container for use in collecting a -sample of material, the container having a resiliently deformable sampling area at its base the sampling area being deformable into the container.

12. A container as claimed in claim 10 which has a plurality of compartments each with a resiliently deformable sampling area at its base.

13. Sampling apparatus comprising sampling means having at least one resiliently deformable sampling area, and means for deforming the area to bring it into contact with material to be sampled.

14. Sampling apparatus as claimed in claim 13 wherein the means for deforming the are is a reciprocable plunger.

15. Sampling apparatus as claimed in claim 13 wherein the sampling means is an elongate strip having a plurality of longitudinally spaced resiliently deformable sampling areas, and means area provided for advancing the strip such that the sampling areas more successively to the sampling position.

16-. Sampling apparatus as claimed in claim 13 wherein the sampling means comprises a container with at least one resiliently deformable sampling area.