DE69119647T2 - Capillary vaccinator and arrangement and method for vaccinating a variety of test fields - Google Patents

Abstract

A capillary inoculator assembly is provided for inoculating multiple test sites with small, precise volumes of inoculum. The inoculator employed in the assembly includes a trough-shaped carrier and one or more rows of capillaries extending therethrough. The capillaries extend through one or more rows of projections which form the lower part of the carrier. They are completely filled by capillary action, and the inoculum is retained therein by forces of adhesion and surface tension. A test device may be employed in conjunction with the capillary inoculator and includes discrete test sites which are aligned with the ends of the respective projections. Each of the test sites may be provided with an absorbent material such as a cellulose disk. A dry reagent may be deposited upon each disk so that the inoculum may be analyzed by testing equipment or by visual observation. A method is provided which includes the steps of filling the capillaries, aligning the capillaries with the test sites within the test device, and depositing the liquid inoculum on the respective test sites through wicking action or other procedures. A method is also disclosed for providing a plurality of discrete, liquid samples having small, precise volumes from a quantity of liquid which may be of indeterminate volume. <IMAGE>

Description

The invention generally relates to an inoculator for inoculating test sites with small amounts of a liquid or suspension. The inoculator is suitable for dividing a liquid sample into small, discrete volumes and for dispensing these volumes.

Many laboratory procedures in the fields of microbiology and chemistry require the division of a liquid sample into small portions of known and usually equal volumes. The most common method for dividing and dispensing such samples is called single-channel pipetting. In this method, the liquid sample is drawn into a disposable tube or pipette and dispensed either as a single volume or in smaller, usually equal, increments. The user must position the tip of the pipette over each test site and dispense a sufficient amount of sample into or onto the test site. Care must be taken to ensure that contact between the tip and the test site is reliably excluded, as otherwise the tip will become contaminated. If such contact does occur, the volume of liquid present in the pipette may also be lost.

When using a single-channel pipette, inoculating a large number of test sites can be a labor-intensive task. Although it is possible to use a multi-channel pipette device with multiple tips to reduce the number of steps required to inoculate all sites, this leaves the problem of possible tip contamination unsolved and makes tip positioning more difficult. Single and multi-channel pipettes are generally not used to apply very small liquid samples in the range of 3 to 5 microliters because these pipettes have a very low degree of reproducibility.

A second group of devices for applying small and usually equal volumes of a liquid sample is generally known as "Steers replicators." These replicators have a hand-held body with an array of pins extending downward from the body and arranged as required for the intended inoculation process. Each pin has a blunt, concave, or slotted tip. When the tips of the pins contact the liquid sample, a certain volume of liquid adheres to the lower end surfaces of the pins due to surface tension. The pins are then moved into contact with the test sites so that when the liquid is transferred to them, they are inoculated. The actual amounts of liquid transferred to the test sites depend on the material from which the pins are made, the surface tension of the liquid, the materials present at the test site, and evaporation into the room air. In addition, replicators of this type tend to trap air because the geometry of the tips often prevents the air from escaping during fluid adhesion. In addition to the fact that the replicator is rather bulky and offers only moderate precision, the fluid sample to be transferred through the replicator must be filled into a shallow container so that the pins can be immersed in the sample. The container must then be disposed of carefully without spilling. The replicators are usually made of stainless steel and are therefore not disposable. The replicators must therefore be sterilized after the test sites have been inoculated.

Numerous disposable inoculation devices have been proposed for inoculating test sites containing various substrates for identifying microorganisms. One such device is described in US-A-4,808,316. This device comprises a substantially rigid, planar frame, a plurality of test wells, an inlet manifold in fluid communication with the test wells, and an outlet manifold in fluid communication with the test wells. Each of the test wells contains a suitable reagent which reacts with a liquid sample introduced into the test well. The liquid sample is introduced into the test wells by gravity through the inlet manifold.

Vacuum filling techniques for filling card-formed test wells are described in U.S. Patent Nos. 3,957,583, 4,018,652, 4,116,775, 4,207,394, and 4,318,994. Each of the test wells contains a combination of culture medium, antibiotic, and indicator reagent. Microorganism suspensions are drawn into the test wells by evacuating most of the air from the cavities. When the ambient pressure is then restored, the liquid is drawn in. The light transmittance of the test wells is read through the thickness of the wall.

One of the problems encountered when conducting medical tests is that the sample is often only available in small quantities. There is therefore a need for miniaturized systems to be able to supply small volumes of sample to a measuring field.

Recently, such a system has been developed using multiple disc-shaped or other shaped carriers with a dry reagent coated thereon. The carriers may be made of alphacellulose, pH-neutralized glass fiber, or other such absorbent materials. The carriers may be attached to a holder, such as a card or other surface holder, or placed in test wells formed in a tray. In either case, it is important to inoculate each carrier site with a precise volume of analyte so that the test is accurate and reproducible from site to site and from test to test.

A capillary inoculator according to the preamble of claim 1 is described in GB-A-1 572 596. This inoculator comprises a plate with a plurality of wells, each of which has a capillary opening formed therein. The wells are filled with liquid and the volume remaining in each well is a function of the angle at which the plate or tray is held, as is the case when filling an ice cube tray under a tap.

US-A-4 699 884 describes a tunnel plate with several wells, each having a conical lower end with an outlet opening formed therein. A multiple pipette is inserted into the wells to fill them. The liquid passing through the outlet openings forms a droplet around the conical outer surface of the well.

It is an object of the invention to provide a capillary inoculator, a set containing such an inoculator and a method for using such an inoculator, by means of which exact volumes of a liquid can be formed.

The capillary inoculator according to the invention is defined in claim 1.

The inoculator constructed in accordance with the invention comprises a carrier having a base and side walls defining a reservoir and a plurality of capillaries extending through the base of the carrier and in fluid communication with the reservoir. Preferably, each of the capillaries consists of a bore formed in and extending through the base.

The base of the carrier has a plurality of projections, each of which has the capillaries extending therethrough. The projections preferably have tapered ends similar to the conical ends normally used as the feed ends of a pipette, in order to achieve optimal liquid retention within the capillaries and, on the other hand, to facilitate liquid transfer to the test sites. The use of projections enables the capillaries to be filled by immersing the capillaries in a reservoir. If filling is to be carried out in this way, the carrier does not need to have a reservoir which is formed as an integral part of the carrier. If the reservoir is integrated into the carrier, an absorbent collecting device is preferably provided near the carrier to absorb excess liquid.

The invention further provides an inoculation kit comprising a carrier with a plurality of capillaries extending therethrough and a test device positioned near the carrier, the device containing test sites aligned with the respective capillaries. Preferably, each of the test sites is provided with an absorbent support capable of sucking liquid from the respective capillaries by means of a wicking effect. Preferably, a compressible part is arranged between the carrier and the device in order to separate the ends of the capillaries from the test sites before the start of the inoculation process. By applying pressure to the carrier the ends of the capillaries are pressed into contact with the test sites, thereby transferring the liquid to the test sites. The carrier is preferably provided with a plurality of projections through which the capillaries extend. Preferably, each projection has a tapered end positioned opposite the respective test site.

A method designed according to the invention is defined by claim 8. This method comprises the following steps: providing a carrier with a plurality of capillaries running through it, introducing a liquid into each of the capillaries, aligning the capillaries with a plurality of test sites, and transferring the liquid in each of the capillaries to the respective test sites. Preferably, the transfer of the liquid is carried out by moving the carrier towards the test device until the capillaries contact the respective test sites. Preferably, each test site is provided with an absorbent substrate which draws the liquid out of the capillaries by wicking.

A method of filling the inoculator is also proposed, in which the capillaries are brought into contact with a liquid and then all of the capillaries are completely filled. The capillaries are partially or completely filled by capillary force. By thus completely filling the capillaries - whether by capillary force or by a combination of gravity feed and capillary force - the volume of liquid filled into each of the capillaries is maintained at an exact value.

Fig. 1 shows an exploded perspective view of an inoculator and a test plate according to the invention;

Fig. 2 shows a plan view of the inoculator according to Fig. 1;

Fig. 3 shows a side view of the inoculator according to Figs. 1 and 2;

Fig. 4 shows a sectional view of the inoculator/test plate set in a first position of the inoculator and the test plates relative to each other;

Fig. 5 shows a sectional view of the inoculator/test plate set in a second position of the inoculator and the test plates relative to each other;

Fig. 6 shows a sectional view of an alternative embodiment of an inoculator constructed in accordance with the invention positioned over a test plate ; and

Fig. 7 shows a sectional view of this alternative embodiment in which the inoculator engages the test plate.

The invention provides a set 10 for inoculating test sites with exactly reproducible and optionally equal volumes of a suspension or other liquid sample. The set has an inoculator 12 and a test device which can be designed as a plate 14 adapted to the inoculator. Between the inoculator 12 and the test plate 14 is positioned a compressible part, e.g. a foam ring 16, which, when in its "relaxed" position, separates the inoculator 12 and the test plate 14 by a sufficient distance.

The inoculator comprises a substantially trough-shaped carrier 18, which is preferably formed in one piece and made of a polymer material, e.g. transparent polystyrene resin, It is important that the resin is of a high degree of purity and that no silicone release agents are used during the molding process. This is necessary in order to produce an inoculator that has clean surfaces with high hydrophobicity, the importance of which will be explained later.

The carrier 18 includes a base 20 having a substantially flat upper surface 22, circumferential side walls 24 extending from the upper surface 22, and two rows of capillaries 26. The base and side walls form a reservoir or bowl. Each of the capillaries extends through the base and has an upper opening exiting the upper surface 22 of the carrier base and in fluid communication with the reservoir. Filling of the capillaries is facilitated when the capillaries are substantially adjacent to the side walls 24.

Two series of projections 28 extend from the lower surface of the support base 20. Each projection has a tapered end 30 located near the bottom opening of the capillaries. These tapered ends of the projections, which together with the support base 20 and the projections define the walls of the respective capillaries 26, serve to retain liquid within the capillaries. Although projections with flat bottoms or no projections at all could be used, in these cases the liquid would tend to flow through the capillaries and form drops hanging from the respective flat bottom surfaces. The preferred tapered ends force the liquid to run back up each beveled edge, which would otherwise not readily occur. Another advantage of the tapered ends of the projections is that they increase the probability of correct contact of the capillaries with the test sites with which the capillaries are in This process will be discussed in more detail below. It is important that the bottom surfaces of the ends of the projections do not have a significantly higher wettability than the inner walls of the capillaries, as the inoculum could pass through the capillaries and potentially contaminate the work area or test sites.

The capillaries formed in a single inoculator may have the same or different volumes, each ranging from about one to twenty-five microliters. The inoculator 12 shown in Figures 1-5 is designed to inoculate sixty-four disk-shaped supports 32 with equal volumes of liquid or suspension. (In this specification, the terms "liquid" and "suspension" are used interchangeably.) The supports may be in the form of absorptive disks, hydrophilic membranes, or other substrates, depending on the tests intended. Microwells may also be inoculated with liquid from the respective capillaries. Each capillary has tapered inner walls 34 that taper from a diameter of about 0.055 inches (0.140 cm) at the upper surface 22 of the support base to a diameter of about 0.040 inches (0.102 cm) at the open end of each projection 28. The length of each capillary is about 0.12 inches (0.30 cm) and accordingly the capillary has a volume of about 3.5 microliters.

The capillaries of the inoculator 12 used in accordance with the preferred embodiment of the invention have such tapered, preferably conical, inner walls 34 that the process of manufacturing the inoculator is facilitated. A long, thin core pin in the dimension range of the capillaries cannot be pulled out of the molded part without damaging it or causing abrasion of the pin if the pin does not have a pull angle. Although the inoculator 12 shown and described here does not required, a capillary formed larger at its upper portion than at its lower portion can reliably hold a larger volume of liquid as compared to a capillary of uniform diameter. The range of acceptable capillary diameters depends on the properties of the material of the capillaries and the liquid held in the capillaries, the range of acceleration over which the capillaries are to hold the liquid by surface forces, the method by which the inoculator is filled with liquid, and the method used to remove liquid from the inoculator. In the preferred embodiment of the invention, removal of liquid from each capillary 26 is accomplished by wicking the capillary into a small absorbent support containing the reagents with which the liquid is to react. With this type of removal, the minimum diameter of the bottom of the capillary must be several times larger than the effective pore size of the absorbent support. Accordingly, for a particular support as described below, the minimum diameter may be 0.001 inch (0.00254 cm). However, such a small diameter presents great difficulty in molding and slows the intended discharge of the liquid. In other applications, compressed air or other pressurized gas may be applied to the capillaries from above to discharge the liquid, or the liquid-filled device may be subjected to controlled acceleration. In these methods of removal, there are no definite lower limits on the diameter of the capillaries other than those imposed by the method of manufacturing the device and the required rate of liquid removal.

The maximum diameter of the bottom of each capillary 26 is determined by the need to keep the liquid in the flow during acceleration processes that may occur at any desired or likely movements of the inoculator 12 between the time the capillaries 26 are filled and the time the liquid is intended to be removed. The inertial forces resulting from such accelerations must be overcome by the surface tension forces at the surface of the liquid. In the preferred embodiment of the invention, an aqueous liquid containing a wetting agent at a low concentration is held in polystyrene capillaries each having a length several times (i.e., 2-4 times) its average diameter. Manual manipulation of the filled device is required to dispense the liquid. The practical upper limit for the diameter of each capillary is approximately 0.1 inch (0.254 cm). With a smoother movement of the inoculator, a more wettable capillary material, a liquid with a higher surface tension and a larger diameter can be used. The maximum diameters mentioned also depend on the length of the capillary and the direction and magnitude of the acceleration. In general, there must be resistance at least to gravity.

The maximum diameter at the top or liquid entry end of the capillaries is limited by the volumetric accuracy desired when the capillaries are filled by flowing a liquid across the capillaries, which is the preferred filling method for the inoculator disclosed herein. If the diameter becomes too large, the volumetric accuracy suffers due to deviations in the shape of the liquid surfaces left as the flowing liquid separates from the liquid retained in the respective capillaries.

If desired, the capillaries can be filled from below by capillary rise. The projections are filled via immersed in a liquid for a period of time sufficient to completely fill the capillaries. Preferably, the capillaries are filled simultaneously. In this case, the maximum diameter of the top (and all other areas) of each capillary is determined by the requirement that the surface tension of the liquid, the angle of contact of the liquid with the capillary material, and the diameter ensure that each capillary is filled to the top. In this way, volumetric accuracy is achieved.

A transparent polystyrene carrier as described herein, used with microbial suspensions to seed absorbent supports, will function as intended when each capillary has a volume between three and ten microliters. Using other materials and/or design parameters, capillary volumes in the range of 1-25 microliters may be used. Generally speaking, the capillaries are designed such that the volume of liquid retained by all capillaries is the same at filling and remains the same for up to ten minutes prior to transfer without inadvertent release or significant evaporation. Using the parameters described above, these goals can be achieved.

Referring to Figures 1, 2 and 4, the inoculator 12 comprises a carrier which is formed as a long, narrow trough with an elongated central rib 36 which separates the two rows of capillaries from each other. (The rib 36 should be omitted if it causes difficulty in filling the capillaries.) At one end of the carrier there is provided a filling area 38 which is free of capillaries. The filling area 38 has a sloped upper surface 40 which adjoins the upper surface 22 of the carrier base 20 at one end and which is in contact with three surface areas of the peripheral side walls 24 at adjacent to these walls 24. Thus, a liquid applied to the upper surface 40 of the filling area tends to move towards the upper surface 22 of the support base 20 in which the upper openings of the capillaries 26 are arranged.

An overflow basin 42 for excess inoculum is formed integrally with the support base 20 in an offset position from the rest of the reservoir. A second rib-like projection 44 having a sloped surface 46 adjacent to the main reservoir area separates this reservoir area from the overflow basin 42. A sponge 48 or other absorbent material is positioned in the overflow basin. Any absorbent material may be used in the overflow basin provided it does not release dust or fiber contaminants into the capillary area and is not altered by the inoculum.

Two sideways extending flanges 50 each extend from one side of the support base 20. One of the flanges has a relatively large area 52 that can be used for gripping the inoculator and/or for attaching an identification tag to the inoculator.

A plurality of feet 54 extend downwardly from the bottom surface of the support 18. These feet serve to raise the capillary ends out of contact with the work surface and also provide positioning aids for aligning the inoculator with the test plate when the inoculator is attached to the test plate in the manner to be described.

A transparent cover strip 56 made of adhesive-coated clear MYLAR (TM) or other liquid-impermeable material is attached to the upper edges of the peripheral wall 24 of the carrier 18. This tape covers all areas of the carrier with the exception of the filling area 38.

The structure and configuration of the device to be inoculated by the inoculator 12 of the present invention will depend on the particular use to which the device is put. Several of these devices are disclosed in EP-A-0 347 771 entitled "Device For Enhancing Fluorescence And Kinetics And Methods Of Using The Device", which is hereby incorporated by reference into the present specification.

The test plate 14 shown in the figures is molded from polypropylene or other suitable polymeric material. Referring to Figures 1 and 2, the test plate 14 has a substantially flat rectangular body 58 having an elongated land region 60 with a flat upper surface 62 formed thereon. Sixty-four cylindrical test wells 64 are provided, each having an upper opening exiting at the upper surface 62 of the elongated land region 60 and a lower opening exiting at the bottom surface 66 of the test plate. The diameter of each well is greater than the diameter of the projections 28 extending from the inoculator. The depth of the wells 64 is less than the length of these projections. Optionally, position reference notches 68 may be formed in the longitudinal edge of the test plate closest to the wells, each aligned with a respective well. A label 70 may be attached to the upper surface of the plate to indicate plate data.

A transparent, liquid-impermeable adhesive tape 72 is attached to the lower surface 66 of the test plate 14. This tape may be an acrylic, adhesive-backed strip of clear MYLAR (TM) or other suitable polymeric material. As shown in Fig. 4, the tape 72 is attached to the lower surface 66 of the test plate 14. The Belt 72 provides an adhesive bottom for each of the cylindrical wells 64. The disks or membranes 32 are respectively attached to the adhesive bottoms of the cylindrical wells 64 and provide the test locations at which the test data is collected.

A notch 72 is formed in one of the ends of the test plate 14 to receive one of the feet 54 extending from the inoculator 12. Near the opposite end of the test plate 14, two openings 74 are formed to receive the other two feet 74 of the inoculator 12. The test plate itself may be provided with a plurality of feet 76 for ease of handling, positioning the test plate in a test instrument and protecting the transparent band 72. A ventilation channel 78 extends between the end of the elongated land region 60 and an edge of the test plate.

The disk-shaped supports 32 arranged in each of the cylindrical test wells 64 are preferably made of an absorbent material such as alphacellulose or pH-neutralized glass fiber. A particularly preferred material is alphacellulose in the form of lint cotton paper. The disks should have sufficient thickness to absorb an effective amount of the reagent intended to react with the liquid inoculum in question. When the supports are formed in the form of pieces of filter paper, a thickness of 0.2 mm to 2.0 mm has generally proven to be suitable. In these cases, a solution of test reagent is absorbed by the supports and dried before they receive the liquid inoculum from the inoculator 12. For such analysis purposes, the supports preferably have a thickness of 0.5 mm to 0.9 mm.

The shape of the supports arranged in all test wells 64 is not critical. The thickness of the support, in conjunction with the surface area, determines the volume of liquid required to completely wet each support. is required. The void volume of each support is preferably between approximately one microliter and twenty-five microliters.

In operation, the liquid inoculum is introduced into the reservoir of the carrier 18 by pouring or pipetting it into the fill area 38. A desirable feature of the invention is that the volume of sample introduced into the inoculator can be varied over a wide range, e.g., 300 to 1000 microliters, without affecting the accuracy of the volumes applied to the test sites.

The liquid inoculum placed in the carrier generally does not have sufficient volume to cover all of the capillaries simultaneously when filled. Because of the hydrophobic surfaces defining the reservoir, the liquid inoculum tends to form a rolling mass that covers only about one-quarter of the capillaries. However, no additional liquid is required, thus avoiding wastage of inoculum. After the entire volume of liquid inoculum has been filled into the filling area 38, the operator tilts the inoculator 12 slightly toward the overflow end to move the liquid mass sequentially over the upper ends of the capillaries, filling each of the capillaries as it is covered with liquid. Filling is accomplished partly by gravity flow, but primarily by capillary action. The double well defined by the side walls 24 and the elongated rib 36 is sufficiently narrow so that each capillary must be filled as the liquid moves over it. If no rib is used, the distance between the side walls must be sufficiently narrow to ensure that the liquid penetrates into each capillary. Once all the capillaries are filled and the excess liquid has drained off the the end provided with the catch basin, the inoculator is tilted 30 to 40° about its longitudinal axis toward the catch basin itself so that the liquid flows over the rib 44 and into the sponge 48 of the overflow basin. The hydrophobic surfaces of the carrier retain substantially no liquid in the channels above the capillaries. The cover strip 56 helps prevent spillage.

The liquid introduced into the capillary inoculator 12 preferably contains a visible dye to confirm that all capillaries are completely filled. When viewed from the top of the carrier 18, the capillary cavities are relatively long and narrow. Thus, a small amount of dye is easily visible; a partially filled capillary is identified by a lighter shade of color.

Alternatively, by choosing a liquid that has the same refractive index as the plastic from which the capillaries are made, the need to use a dye can be eliminated. Confirmation that each capillary is filled is not provided by a relatively dark column of liquid, but by the effect of an optical disappearance of the bore of the capillary when the capillary is filled.

The inoculator 12 is preferably, but not necessarily, mounted to the test plate 14 prior to filling. The foam ring 16 or other resilient separator disposed between the inoculator and the test plate must be sufficiently rigid to prevent contact between the projections 28 and the disk-shaped supports 32 during normal handling. Furthermore, the capillaries themselves should be of a suitable size and configuration to withstand normal handling - including turning the inoculator on edge or in an inverted orientation.

- to prevent liquid from being released by shaking.

The transfer of liquid from the inoculator 12 to the test sites located in the test plate 14 is preferably mechanical. A self-aligning plate (not shown) is pressed downwardly onto the top of the inoculator, forcing the ends of the capillaries into contact with the supports 32 as shown in Figure 5. If the supports are sufficiently absorbent, upon such contact the liquid will be rapidly and substantially simultaneously moved out of the capillaries by wicking. Although this process can be performed manually, for many applications it is important that instrument readings be taken immediately after inoculation. Reproducible tests could not be consistently performed by manually initiated inoculation. As previously explained, inoculation may also be performed by gas pressure over the capillaries or by sudden acceleration of the inoculator.

Depending on which reactive substrates are contained in all supports 32, the appropriate tests can be carried out following inoculation. The reactions between the inoculum and the substrate can in some cases be observed visually. Since there is no rapid evaporation of the liquid from the capillaries, it is not critical that the inoculation of the test sites be carried out immediately after filling. The foam ring 16 protects the ends of the capillaries from all air currents, and the cover strip 56 protects the upper openings of the capillaries. Evaporation is thus minimized.

While performing instrument readings, the inoculator is in the position shown in Fig. 4.

Alternatively, the inoculator can be removed from the test plate and put away.

If desired, the sponge 48 or other absorbent material disposed in the inoculator may contain a reagent dried thereon. When excess inoculum is drained into the overflow basin, a large volume of analyte is brought into contact with the reagent. Indication of a positive result may be by a visible color change or a fluorescent reaction. This procedure is suitable for tests that require a relatively large volume, but not a precise volume, as opposed to those performed at the test sites of the test plate 14, which require small, precise samples.

The inoculator 12 and inoculation method described above offer a number of significant advantages in situations where small, precise amounts of liquid inoculum must be applied to test sites. Since no pressure or suction is required to transfer the inoculum, errors caused by air compressibility are avoided. Filling the inoculator in a single pipetting step or pouring operation does not require high positional or volume accuracy. The inoculum is divided into a number of precise volumes in a single operation. The individual volumes of inoculum are isolated from one another, preventing cross-contamination when transferring the inoculum to the test sites. Excess inoculum is captured within the inoculator, preventing spillage, accidental contact, and mismeasurements of the amount of inoculum transferred to all test sites. By using the inoculator in the manner described, good accuracy and reproducibility can be achieved even when simultaneous inoculation of test sites with volumes of five microliters or less. The inoculator allows visual inspection of correct filling of the capillaries and ensures that the liquid contained in the capillaries is not significantly affected by evaporation during the normal period between filling of the capillaries and inoculation. The liquid is retained in the capillaries regardless of the orientation of the inoculator.

Figs. 6 to 7 show an alternative embodiment of the invention. The set 10' shown in these figures is essentially similar in structure and function to the set according to Figs. 1 to 5, but is preferably intended for handling relatively small volumes of liquid.

The kit includes an elongated inoculator 12' and a mating test device 14'. The inoculator 12' can be secured to the test device 14' by conventional locking snap devices (not shown) integrally formed in the respective components. A pair of resilient projections 16' positioned between the inoculator 12' and the test device 14' on opposite sides of the kit 10' maintain the inoculator 12' in the raised position shown in Fig. 6. Only one of the projections is shown in Fig. 6.

The use of the projections 16' instead of a foam ring 16 allows air to pass through the set. Therefore, to minimize evaporative losses, the inoculator 12' has wall portions 17' which fit into a substantially oval groove 19' surrounding the test wells 64' formed in the test device 14'. The relative positions of these wall portions 17' and the outer walls 21' of the test wells 64' impede the flow of air through the sub-regions of the capillaries 26' so that the evaporation which would otherwise occur is reduced.

The inoculator 12' has a support 18' with a flat upper surface 22' and peripheral side walls 24' which project from the flat upper surface. The capillaries 26' run substantially tangentially to the side walls to facilitate the entry of liquid. No rib is provided between the rows of capillaries. A flange 52 is also provided which is substantially similar in structure and function to the flange 52 of the embodiment according to Figs. 1 to 5.

The structure of the test device 14' is similar to that of the embodiment described above, with the certain exceptions already mentioned. In addition to these exceptions, the disk-shaped supports 32' are attached to the bottom surface of the test device itself rather than to the tape discussed above. Filling of the inoculator 12' and inoculation of the test sites are carried out in essentially the same manner as explained in connection with the inoculator 12 described above. During filling, the inoculator 12' is arranged in the position according to Fig. 6, and inoculation takes place after the inoculator 12' has been moved to the position according to Fig. 7. Upon contact of the projections 28' with the absorbent test sites, substantially all of the liquid is dispensed from each capillary 26'.

Claims (9)

1. Capillary inoculator (12) for dividing a liquid inoculating agent into several volumes and inoculating several test sites, with: a carrier (18) having a base (20), side walls (24) projecting upwards from the base, and optionally a cover (56) attached to the side walls (24) of the carrier (18), the base and the side walls forming a reservoir, and a plurality of capillaries (26) which are in fluid communication with the reservoir and each extend through the base (20), characterized by a plurality of projections (28) extending from the carrier (18) through which the capillaries (26) extend, each of the capillaries (26) being capable of retaining a liquid inoculant subjected to at least gravity by surface tension and adhesion, and each of the capillaries (26) having a pair of open ends so that the capillaries (26) can be filled by capillary action. 2. A capillary inoculator according to claim 1, wherein the base (20) and the side walls (24) form an elongated reservoir having a pair of opposite ends and an overflow basin (42), and which is provided with means (44) for separating the reservoir from the overflow basin (42). 3. Capillary inoculator according to claim 1 or 2, wherein each of the projections (28) has a tapered lower end (30). 4. Set for simultaneous vaccination of several discrete test sites, with: an inoculator (12) according to any one of claims 1-3, and a device (14) arranged adjacent to the inoculator (12) for receiving liquid inoculant from the inoculator, the device (14) having a plurality of discrete test sites (32,64) and all of the outlet ends of the capillaries (26) being aligned with one of the test sites (32,64). 5. Set according to claim 4, with a compressible part (16) arranged between the inoculator (12) and the device (14), the outlet ends of the capillaries (26) being positioned such that they each contact the test sites (64) when the inoculator (12) is moved a certain distance towards the device (14), and the compressible part (16) is compressed when the inoculator (12) has been moved the certain distance towards the device (14). 6. Set according to claim 5, wherein the carrier forms a reservoir which is in fluid communication with the capillaries (26). 7. Set according to claim 5, wherein the test points (32,64) are formed by a plurality of test points arranged within the device. Troughs (64) are formed, and which optionally has a plurality of absorbent supports (32) which are each positioned within the test troughs (64). 8. A method for forming multiple discrete liquid samples having small, precise volumes using the capillary inoculator (12) according to claim 1, comprising the following steps: Introducing a liquid into the reservoir; causing the liquid to contact each of the capillaries (26) for a period of time sufficient to substantially completely fill the capillaries by capillary action or a combination of gravity and capillary action; Providing a test facility (14) with several test points (32,64); Aligning the capillaries (26) with the respective test points (32,64); and Transfer the liquid contained in each of the capillaries (26) to the respective test site (32,64). 9. The method of claim 8, comprising the steps of providing a compressible chamber (16) between the inoculator (12) and the test device (14), and pressing the inoculator (12) toward the test device (14) to thereby compress the compressible chamber (16) and bring the outlet ends of the capillaries (26) into contact with the respective test sites (32,64).