GB2422663A

GB2422663A - Device for surface assay

Info

Publication number: GB2422663A
Application number: GB0501685A
Authority: GB
Inventors: Martyn Johnson-Townley
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-01-27
Filing date: 2005-01-27
Publication date: 2006-08-02
Also published as: GB0501685D0

Abstract

A surface assay device including means to automatically take a sample from a surface by issuing a swabbing fluid from an emitter means 1, thus causing the swabbing fluid 5 to flow across the surface. The swabbing fluid is collected by a receiver means 3. Conduits 4 conduct the swab to reaction chambers 17. Different configurations of said conduits and chambers being able to replicate the methodology of specific tests on said swab. Any intermediate steps of the methodology are reproduced by conducting intermediate products of reaction along intermediate conduits to intermediate reaction chambers and then to a result chamber 17. There is a means of communicating information regarding said result to an observer. A corollary of this invention is a small format device to stick-on human skin for the ongoing detection of MRSA.

Description

A device for surface assay This invention relates to a device for

detecting and reporting contamination on surfaces. Many situations demand the assay of surfaces for contamination.

For example: the control of nosocomial infections. In particular, Methicillin resistant Staphylococcus aureus, sometimes known as MRSA, has emerged all over the world.

It is incumbent upon hospital authorities to maintain regimes that assess whether a patient is a carrier of such infections. The ideal would be to monitor all patients and surfaces in a hospital by continuous swabbing and testing. However, resource constraints make this ideal generally unobtainable, insufficient manpower is available to continuously process swabs and maintain a continuous audit of the levels of contamination on all surfaces and on the skin of all patients and healthcare workers.

This ideal could, however, be approached if the swab and test procedure could be incorporated in a single device. The device could then be applied to one or more sites on a patient's skin. In effect the laboratory is "brought to the patient". This concept can be extended to the health care worker, the hospital visitor and even testing of the entire community. Beyond this, various manifestations of the present invention could bring generalised assay to any surface.

So we have the idea of a generalised surface assay device. The device has the means to automatically take a sample from the surface on which it is deployed. Inside the device there is a micro-engineered network of reaction chambers and reservoirs joined by conduits. The sample and the reagents are deployed throughout the network by capillary action according to the methodology of the required test. The present invention also admits the possibility of other means, possibly including an internal energy source, to promote fluid flow through the network.

To address these issues the present invention proposes a surface assay device including means to automatically take a sample from a given surface and including a means of conducting said sample to a chamber within said device where the device includes the means to perform a test on the sample, said device including a means to communicate information regarding the results of said test to an autonomous device or to a person.

Embodiments of the present invention could include any engine capable of automatically taking a sample from a surface. An implementation using currently leading edge technology could use a micro-engineered motor driving a system of vanes and paddles to draw a sample from the surface. This sampling engine would use a miniaturised power supply. More esoteric would be a motor/impeller system engineered at the molecular level. However, all of the embodiments described herein use capillary action and fluid flow across the surface as the sampling mechanism.

The same comments apply in principle to the mechanism whereby fluids are driven along conduits and through chambers within the assay device; for many methodologies capillary action will be sufficient but implementations using micro- or molecular-engineered pumps at requisite points within the network of conduits and chambers are possible.

An embodiment of the present invention is a skin assay device that can be left in place for a length of time on the skin of a patient. The device would be small and unobtrusive, say, no more that 1cm2 in area. The assay device is able to automatically take a sample from the host surface once it has been deployed.

An embodiment of the present invention uses a receiver to take up a sample from human skin. The receiver uses capillary action to take up the sample, after the fashion of a sponge. This provides an adequate sample when liquid is already present on the surface to provide a swab, for example, sweat on human skin. In another embodiment of the present invention, an emitter of swabbing fluid as well as a receiver would be necessary, for example if the surface was dry or too dry to admit of itself the possibility of sample taking by capillary action.

The emitter takes the form of swabbing fluid issuing from a reservoir at a predetermined rate. A further advantage of this embodiment is the ability to continuously swab the surface as opposed to a technician taking an instantaneous swab. Moreover, we now have the opportunity to make the parameters of the swabbing action well defined in terms of duration, overpressure, flow-rate and the area addressed by the swab. A technician relies on experience to judge dwell time, swabbing pressure and swabbing action -all parameters susceptible to undesirable variation according to the human factor.

Each of the plurality of emitters is physically oriented to promote the sampling action and the flow of swabbing fluid towards its corresponding receiver. Flow of swabbing fluid from the emitter, across the surface to be assayed, to the receiver begins when the assay device is deployed. For example when a sticky backing is removed and the device is positioned on human skin.

The sample is conducted by capillary action from the receiver along the conduits to reaction chambers within the surface assay device. The conduits and chambers of the surface assay device are arranged in order to duplicate the methodology of a given test.

Each chamber of the surface assay device is specialised. A chamber may contain any reagent or substance necessary for a given test methodology.

A chamber may be specially constructed to implement an aspect of the methodology.

For example, some microbiological tests require that a detection medium be confined between thin glass plates after having been streaked or stabbed with inoculum. The essential features of such a methodology are reproduced by micro-engineering in the present invention. Selective detection medium is confined between glass plates. The inoculum is introduced to the medium by capillary action. Streaking of the plates is achieved by leading the inoculum between the plates by means of capillary filaments or by capillary flow into the body of the detection medium.

A typical scenario would involve having numerous surface assay devices deployed on a patient's skin. Deployment would simply involve peeling the backing from a sequence of assay devices and sticking them to various skin locations, probably in a predetermined pattern, according to the likelihood of a location harbouring a pathogen. Due to the small and unobtrusive nature of the devices intimate locations such as nasal interiors or anal surrounds could be addressed.

Subsequent interrogation of the assay devices would involve an operative observing the assay devices possibly using an illuminated magnifying glass or light pipe to observe changes in the view port of each assay device. The operative would be observing changes in color, turbidity or bioluminescence according to the methodology being implemented by the surface assay device.

An advantage of the present invention is that the operative can interrogate a device at fixed intervals, say every 2 hours, after the initial deployment; in effect giving an ongoing assay of the patient's skin. Each time the operative makes an observation is equivalent to a "swab - lab - result" cycle. In essence the "swab - lab - result" cycle has been brought to the patient's skin. For many tests that have suitable chemistry and methodology the assay is continuous.

The present invention facilitates multiple site sampling. Clinical trials have shown that an increase in the number of sites sampled will increase the rate of MRSA detection.

The present invention permits, for instance, cheap mass-deployment of skin assay for methycillin resistant Staphylococcus aureus. Once infection is strongly suspected by way of the present invention a patient can be assayed using a "gold standard" test such as expression of the mecA gene by way of confirmation. Resource intensive testing can, therefore, be concentrated on absolute confirmation.

In another manifestation the device would have a "grain of rice" or "doughnut" format and could be deployed in or around a wound.

The present invention is particularly suited to tests that must be made over a period of time at body temperature. The present invention also admits embodiments using an internal power supply to maintain temperature or environmental levels within the surface assay device.

The present invention can be adapted to many test methodologies.

The invention will now be described by way of different implementations and with reference to the accompanying drawings in which: Figure 1 shows the layout in plan of a specific embodiment of a surface assay device to perform a plated mannitol-salt medium test on human skin consisting of a substrate supporting a plurality of emitters and receivers and conduits to a central annular plate chamber.

Figure 2 shows the layout in plan of a second embodiment of a surface assay device to perform a plated mannito 1-salt medium test consisting of a substrate supporting a plurality of receivers and conduits to a central annular plate chamber.

Figure 3 shows in plan a result chamber containing plated medium, within the medium and making intimate contact with the medium is a network of capillary filaments.

Figure 4 shows in section a result chamber containing plated medium.

Figure 5 shows a second embodiment of the present invention that has a doughnut form with a flat central result complex and is adapted to assay a wound.

A "selective" medium in this description is one that encourages growth of a particular organism by discouraging the growth of other organisms.

A "differentiator" in this description offers visible indication of a chemical reaction having taken place due to a physiological property of a particular organism.

In figure 1 we see the device in plan lying on human skin. Note that this embodiment is symmetrical. There are three outer' elements each subtending 1200. This is purely conventional: an embodiment can manifest itself with any number of similar elements and not necessarily with the circular footprint depicted. For example an elongated format might lend itself to easy deployment in fold of skin -such as the groin. The embodiment is realised within a postage stamp' footprint by precision micro engineering.

in figure 1 the results chamber is annular in plan. Inside said chamber are two or more annular plates between which is confined the selective medium 17.

The composition of the substrate 7 (figure 4) is chosen to promote ease of micro engineering of conduits, chambers, emitters and receivers. In this manifestation of the present invention the substrate is chosen to have adequate flexibility in view of the necessity to mount the device on human skin.

The act of removing the backing in figure 1 to deploy the device cleaves seals 23.

The cleaving of seals 23 causes swabbing fluid to flow 5 from chambers 2 along conduits 4 that deliver to emitter arrays 1. In all figures fluid flows 5 are denoted by solid arrows.

Swabbing fluid flows 5 from the emitter arrays 1 to the receiver arrays 3. As the swabbing fluid flows across the skin a sample is taken. The fluid flows 5 continue along the conduits 4 towards the annular results chamber 20. The results chamber 20 contains selective medium 17. In figure 1 we see that fluid flow is assisted by the presence of a sump' area 22 in the middle of the annulus.

In figure 2, we see a simplified embodiment of the present invention. The emitter arrays are omitted. Swabbing fluid is already present on the surface, for instance human sweat on skin, so a swab is taken by the flow of fluid directly into the sponge like receiver arrays 3.

In figure 3, we see a more generalised results chamber that is disposed linearly. It has one flow inS and one flow out. In figure 3 the fluid flowS continues into the result chamber 20 and is drawn by capillary action along filaments 6 located within the body of the selective medium 17 (figure 4) and between the plates 12 and 13 (figure 4).

Note that the filaments have been laid down irregularly but a regular lattice would be equally effective, the objective being to bring the flow of swab fluid into intimate contact with the selective medium between the plates.

In figure 4 we see part of the results chamber 20 of figure 3 in section. In figure 4 there are several added optical refinements shewn conventionally. The substrate 7 of the device sticks to human skin 21 by virtue of an adhesive layer 8.

In figure 4 we have oxacillin-salt agar medium 17 confined between the upper plate 12 and the lower plate 13 in the results chamber 20 (Figure 3).

The oxacillin-salt agar medium 17 is a selective for Staphylococcus aureus and has a differentiator. The medium 17 has the following composition: 6p.gImL oxacillin plus 4% NaCI plus pH indicator phenol red in mannitol agar. Non resistant Staphylococcus aureus is inhibited by oxycillin if it is present in an inoculum. The phenol red acts as a differentiator in the selective medium. Phenol Red has an orange color near pH neutrality. Resistant Staphylococcus aureus will ferment the mannitol which is a carbohydrate. This will cause lowering of the pH and a consequent and observable yellowing of the differentiator.

The swab from the surface containing the inoculum is introduced to the medium 17 by capillary action. The flowS of swab is shown in figure 4 passing between the plates 12 and 13. The flowS of swab is in intimate contact with the medium 17. Streaking of the plates is achieved by leading the swab between the plates 12 and 13 (figure 4) by means of capillary filaments 6(figure 3). Filaments 6 are omitted in figure 4.

In some manifestations of the present invent capillary action alone will suffice to allow the swab to disperse into intimate contact with the medium 17, thereby permitting omission of the filaments 6 (figure 3). The plate spacing and viscosity of the medium can be calculated exactly to promote these preferred conditions.

The two plate 12 & 13 configuration described in figure 4 does not preclude the use of further plates to achieve multiple layers of detection medium 17.

In figure 4 the observer 14 is looking through the view port 16 for color change in the oxacillin-salt agar medium 17.

Because of the anticipated small size of the surface assay device optical aid 10 & 15 & 11 is an option to assist the observer to inspect the results chamber although this is not a necessary refinement of the present invention. An optional light pipe 18 shining through a port 19 provides a source of illumination. An optional lens 11 optimises field of view to the plane of the medium 17. Figure 4 shows a reflective backing to the plate assembly 10 that reflects incident light to assist illumination of the medium 17.

Optics 15 is shown conventionally and represents any suitable lens configuration to aid the observer.

A further refinement of the present invention is optical confirmation of flow of swabbing fluid in any chamber or conduit by the addition of microencapsulated dye which changes color in the presence of swabbing fluid in order to give confirmation of correct operation of the device.

In other embodiments of the present invention the selective medium could be any mucilaginous material used as a base for bacterial culture containing antibiotic or a plurality of antibiotics to which Methicillin resistant Staphylococcus aureus is no- longer susceptible. This would have the effect of isolating strains of contamination of Methicillin resistant Staphylococcus aureus, again a differentiator would provide visible indication of the result.

Incubation is at body temperature 37 C and 24 hours after deployment on human skin the results chamber is ready for its first inspection.

A second embodiment of the present invention is deployed to assay a wound for mrsa.

The act of deployment merely involves lodging one or more devices in the wound tissues; there being no sticky backing to remove. This embodiment of the present invention being symmetric about a plane passing through its circumference.

in figures we see in section a second embodiment of the present invention. The form of this embodiment is a doughnut shaped ring enclosing a flat area that contains the annular results chamber. This embodiment of the present invention measures only a few millimetres in diameter. In figure 5 the entire doughnut ring 3 is acting as a capillary receiver. The entire doughnut ring is composed of capillary material. The device is lying on a damp surface, such as an open wound. Swab flowS is directed radially from the exterior to the interior of the device, the doughnut rim of the device acting as receiver to sample the damp surroundings into which the device is embedded. The fluid flows 5 are promoted by capillary action. Once the swab flow S reaches the flat interior of the device it reaches the results chamber 20 without traversing any intermediate conduits.

Results chamber 20 consists essentially of the components described in figure 4. But in this embodiment we have a multiple plate assembly 12. The oxacillin-salt agar medium 17 is a selective for Staphylococcus aureus and has a differentiator. The medium 17 has the following composition: 6pgImL oxacillin plus 4% NaCl (w/v) plus pH indicator phenol red in mannitol agar. Non resistant Staphylococcus aureus is inhibited by oxycillin if it is present in an inoculum. The phenol red acts as a differentiator in the selective medium. Phenol Red has an orange color near pH neutrality. Resistant Staphylococcus aureus will ferment the mannitol which is a carbohydrate. This will cause lowering of the pH and a consequent and observable yellowing of the differentiator.

Having being brought into intimate contact with the medium 17, flow of the swab fluid continues to the sump volume 22.

The results chamber 20 has translucent sides 24 which enable observation of differentiator color changes within the results chamber 20.

Claims

Claims 1. A surface assay device including means to automatically take a

sample from a given surface and including a means of conducting said sample to a chamber within said device where the device includes the means to perform a test on the sample said device including a means to communicate information regarding the results of said test to an autonomous device or to a person.
2. A surface assay device according to claim 1 including means to automatically take a sample from a surface.
3. A surface assay device according to claim 1 in which the mechanism for collecting a sample from a surface is capillary action.
4. A surface assay device according to claim I in which the mechanism for collecting a sample from a surface is a scoop and vane system implemented by micro engineering.
5. A surface assay device according to claim I in which the mechanism for collecting a sample from a surface is a scoop and vane system implemented by molecular engineering.
6. A surface assay device according to claim 1 including an emitter means to introduce a swabbing fluid onto the surface to be assayed.
7. A surface assay device according to claim 6 in which the swabbing fluid remains sealed within a chamber until the device is deployed.
8. A surface assay device according to claim 6 in which the sample from the surface to be assayed is taken by means of the flow of swabbing fluid across the surface.
9. A surface assay device according to claim 6 in which the propagation speed of the swabbing fluid across the surface to be sampled has been adjusted by chemical means.
10. A surface assay device according to claim I including a receiver means to retrieve the swabbing fluid from the surface to be assayed.
11. A surface assay device according to claim 10 in which said receiver means uses capillary action as a means of retrieving the swabbing fluid from the surface to be assayed.
12. A surface assay device according to claim 10 including receiver means and no emitter means where the surface to be assayed effectively provides swabbing fluid of its own accord.
13. A surface assay device according to claim I including a conduit means to conduct the swab from the receiver means to other components of the surface assay device.
14. A surface assay device according to claim 13 in which the swab is conveyed along the conduit means by capillary action.
15. A surface assay device according to claim 14 in which the speed of propagation under capillary action of the swab in a conduit can be varied to suit the required methodology by varying the composition of the capillary material in the conduit.
16. A surface assay device according to claim I including one or more chambers each linked by any number of conduits to other components of the surface assay device.
17. A surface assay device according to claim 16 in which any of said chambers can contain a reagent according to the methodology of the test being undertaken.
18. A surface assay device according to claim 16 in which a chamber may be filled with an inert porous material that is doped with a reagent.
19. A surface assay device according to claim 16 in which any of said chambers can contain a specific detection medium as a reagent according to the methodology of the test being undertaken.
20. A surface assay device according to claim 19 in which the detection medium in the chamber is a variety of salt broth.
21. A surface assay device according to claim 1 in which a results chamber can provide the result of a test by observation of change of any observable in the chamber.
22. A surface assay device according to claim 21 that will give the result of a test by showing a predefined color change in a particular chamber.
23. A surface assay device according to claim 21 that will give the result of a test by showing a change in turbidity in a particular chamber.
24. A surface assay device according to claim 21 in which the result chamber enables observation of the result via a transparent area or viewing port.
25. A surface assay device according to claim 24 in which said result chamber has mirroring behind the chamber in order to make best use of incident light to observe changes in said chamber.
26. A surface assay device according to claim 24 that comprises a viewing port having a lens or other optical enhancement.
27. A surface assay device according to claim 21 in which observation of the result is facilitated by an external means.
28. A surface assay device according to claim 27 in which observation of said result is facilitated by an intense illumination.
29. A surface assay device according to claim 1 that by way of control will show a predefined color change in a given chamber if the test has taken place correctly.
30. A surface assay device according to claim 21 in which the detection medium in a given results chamber exhibits change in its appearance when colonised by a pathogen.
31. A surface assay device according to claim 30 in which the detection medium in a given results chamber has had its chemical composition chosen to raise specificity for a particular pathogen.
32. A surface assay device according to claim 30 in which the detection medium could be any mucilaginous material used as a base for bacterial culture.
33. A surface assay device according to claim 30 in which one or several antibiotics have been added to the detection medium in order to prevent colonisation of the detection medium by specific pathogens.
34. A surface assay device according to claim 30 in which the detection medium is intimately confined between glass plates which are disposed in a fashion selected from the group consisting of two glass plates and multiple glass plates arranged in a stack.
35. A surface assay device according to claim 34 in which the distance between the plates is chosen to promote transit by capillary action of the flow of swab fluid.
36. A surface assay device according to claim 34 in which said glass plates and their associated detection medium are confined within a chamber.
37. A surface assay device according to claim 36 in which an inoculum carried in swab fluid is conveyed to said glass plates and their associated detection medium by the mechanism of capillary action.
38. A surface assay device according to claim 37 in which an inoculum carried in swab fluid is drawn between said glass plates and into intimate contact with said detection medium by capillary action.
39. A surface assay device according to claim 34 and claim 37 in which capillary filaments between said glass plates are connected to said capillary flow of fluid into the chamber in which said glass plates are located.
40. A surface assay device according to claim 39 in which said inoculum carried in swab fluid is brought into intimate contact with the detection medium by means of the capillary filaments between the glass plates.
41. A surface assay device according to claim 16 in which air can access any of the plurality of chambers on deployment in order to facilitate aerobic reactions or growth.
42. A surface assay device according to claim 16 in which air is excluded from any chamber on deployment in order to facilitate anaerobic reactions or growth.
43. A surface assay device according to claim 1 including a substrate with a sticky backing in order to mount the device securely on a surface.
44. A surface assay device according to claim 6 in which the action of deployment will release swabbing fluid from the emitter means onto the surface to be assayed.
45. A surface assay device according to claim 6 in which certain of said chambers containing fluid are sealed during manufacture by a sealing means.
46. A surface assay device according to claim 44 or 45 in which the act of deployment causes cleaving of certain sealing means according to the methodology of the test.
47. A surface assay device according to claim 16 which comprises a specialised chamber acting as a sump to promote fluid flow within the network of said chambers and conduits.
48. A surface assay device according to claim 1 in which a capillary flow can be split at ajunction.
49. A surface assay device according to claim 48 in which said resultant pair of capillary flows can each perform separate parts of the test methodology.
50. A surface assay device according to claim 48 in which said resultant pair of capillary flows can each have different flow rates in order that a test performed in a chamber in one flow can be undertaken before a test in the other.
51. A surface assay device according to claim 48 in which said resultant pair of capillary flows can be recombined after having performed separate tests in each flow.
52. A surface assay device including means to automatically take a sample from a surface by issuing a swabbing fluid from an emitter means, causing the swabbing fluid to flow across the surface to be sampled to a receiver means and including a plurality of conduits, a plurality of reaction chambers, different configurations of said conduits and chambers being able to replicate the methodology of specific tests on said sample by conducting the swab along said conduits to said reaction chambers, the intermediate steps of the methodology being reproduced by conducting intermediate products of reaction along intermediate conduits to intermediate reaction chambers and then to a final reaction chamber in which a result is obtained and including a means of communicating infonnation regarding said result to an autonomous device or to a person.
53. A surface assay device according to claim 52 including means to automatically take a sample from a surface.
54. A surface assay device according to claim 52 in which the mechanism for collecting a sample from a surface is capillary action.
55. A surface assay device according to claim 52 in which the mechanism for collecting a sample from a surface is a scoop and vane system implemented by micro engineering.
56. A surface assay device according to claim 52 in which the mechanism for collecting a sample from a surface is a scoop and vane system implemented by molecular engineering.
57. A surface assay device according to claim 52 including an emitter means to introduce a swabbing fluid onto the surface to be assayed.
58. A surface assay device according to claim 57 in which the swabbing fluid remains sealed within a chamber until the device is deployed.
59. A surface assay device according to claim 57 in which the sample from the surface to be assayed is taken by means of the flow of swabbing fluid across the surface.
60. A surface assay device according to claim 57 in which the propagation speed of the swabbing fluid across the surface to be sampled has been adjusted by chemical means.
61. A surface assay device according to claim 52 including a receiver means to retrieve the swabbing fluid from the surface to be assayed.
62. A surface assay device according to claim 61 in which said receiver means uses capillary action as a means of retrieving the swabbing fluid from the surface to be assayed.
63. A surface assay device according to claim 61 including receiver means and no emitter means where the surface to be assayed effectively provides swabbing fluid of its own accord.
64. A surface assay device according to claim 52 including a conduit means to conduct the swab from the receiver means to other components of the surface assay device.
65. A surface assay device according to claim 64 in which the swab is conveyed along the conduit means by capillary action.
66. A surface assay device according to claim 65 in which the speed of propagation under capillary action of the swab in a conduit can be varied to suit the required methodology by varying the composition of the capillary material in the conduit.
67. A surface assay device according to claim 52 including one or more chambers each liniced by any number of conduits to other components of the surface assay device.
68. A surface assay device according to claim 67 in which any of said chambers can contain a reagent according to the methodology of the test being undertaken.
69. A surface assay device according to claim 67 in which a chamber may be filled with an inert porous material that is doped with a reagent.
70. A surface assay device according to claim 67 in which any of said chambers can contain a specific detection medium as a reagent according to the methodology of the test being undertaken.
71. A surface assay device according to claim 70 in which the detection medium in the chamber is a variety of salt broth.
72. A surface assay device according to claim 52 in which a results chamber can provide the result of a test by observation of change of any observable in the chamber.
73. A surface assay device according to claim 72 that will give the result of a test by showing a predefined color change in a particular chamber.
74. A surface assay device according to claim 72 that will give the result of a test by showing a change in turbidity in a particular chamber.
75. A surface assay device according to claim 72 in which the result chamber enables observation of the result via a transparent area or viewing port.
76. A surface assay device according to claim 75 in which said result chamber has mirroring behind the chamber in order to make best use of incident light to observe changes in said chamber.
77. A surface assay device according to claim 75 that comprises a viewing port having a lens or other optical enhancement.
78. A surface assay device according to claim 72 in which observation of the result is facilitated by an external means.
79. A surface assay device according to claim 78 in which observation of said result is facilitated by an intense illumination.
80. A surface assay device according to claim 52 that by way of control will show a predefined color change in a given chamber if the test has taken place correctly.
81. A surface assay device according to claim 72 in which the detection medium in a given results chamber exhibits change in its appearance when colonised by a pathogen.
82. A surface assay device according to claim 81 in which the detection medium in a given results chamber has had its chemical composition chosen to raise specificity for a particular pathogen.
83. A surface assay device according to claim 81 in which the detection medium could be any mucilaginous material used as a base for bacterial culture.
84. A surface assay device according to claim 81 in which one or several antibiotics have been added to the detection medium in order to prevent colonisation of the detection medium by specific pathogens.
85. A surface assay device according to claim 81 in which the detection medium is intimately confined between glass plates which are disposed in a fashion selected from the group consisting of two glass plates and multiple glass plates arranged in a stack.
86. A surface assay device according to claim 85 in which the distance between the plates is chosen to promote transit by capillary action of the flow of swab fluid.
87. A surface assay device according to claim 85 in which said glass plates and their associated detection medium are confined within a chamber.
88. A surface assay device according to claim 87 in which an inoculum carried in swab fluid is conveyed to said glass plates and their associated detection medium by the mechanism of capillary action.
89. A surface assay device according to claim 88 in which an inoculum carried in swab fluid is drawn between said glass plates and into intimate contact with said detection medium by capillary action.
90. A surface assay device according to claim 85 and claim 88 in which capillary filaments between said glass plates are connected to said capillary flow of fluid into the chamber in which said glass plates are located.
91. A surface assay device according to claim 90 in which said inoculum carried in swab fluid is brought into intimate contact with the detection medium by means of the capillary filaments between the glass plates.
92. A surface assay device according to claim 67 in which air can access any of the plurality of chambers on deployment in order to facilitate aerobic reactions or growth.
93. A surface assay device according to claim 67 in which air is excluded from any chamber on deployment in order to facilitate anaerobic reactions or growth.
94. A surface assay device according to claim 52 including a substrate with a sticky backing in order to mount the device securely on a surface.
95. A surface assay device according to claim 57 in which the action of deployment will release swabbing fluid from the emitter means onto the surface to be assayed.
96. A surface assay device according to claim 57 in which certain of said chambers containing fluid are sealed during manufacture by a sealing means.
97. A surface assay device according to claim 95 or 96 in which the act of deployment causes cleaving of certain sealing means according to the methodology of the test.
98. A surface assay device according to claim 67 which comprises a specialised chamber acting as a sump to promote fluid flow within the network of said chambers and conduits.
99. A surface assay device according to claim 52 in which a capillary flow can be split at a junction.
100. A surface assay device according to claim 99 in which said resultant pair of capillary flows can each perform separate parts of the test methodology.
101. A surface assay device according to claim 99 in which said resultant pair of capillary flows can each have different flow rates in order that a test performed in a chamber in one flow can be undertaken before a test in the other.
102. A surface assay device according to claim 99 in which said resultant pair of capillary flows can be recombined after having performed separate tests in each flow.
103. A surface assay device according to claim 32 that contains a nutrient means.
104. A surface assay device according to claim 32 that has a differentiation means in order to differentiate a particular organism from other organisms.
105. A surface assay device according to claim 32 that has a selective means to inhibit unwanted organisms.
106. A surface assay device according to claim 103 that has mannitol agar as a nutrient.
107. A surface assay device according to claim 103 that has MuellerHinton medium as a nutrient.
108. A surface assay device according to claim 104 that has phenol red as a differentiator.
109. A surface assay device according to claim 103 and claim 105 that has oxacillin screen agar as a nutrient and selective means.
110. A surface assay device that has NaCl as a selective means.
111. A surface assay device according to claim 32 which has detection medium of the following composition 6jtg/mL oxacillin plus 4% NaCI plus phenol red in mannitol agar nutrient.
112. A surface assay device according to claim 83 that contains a nutrient means.
113. A surface assay device according to claim 83 that has a differentiation means in order to differentiate a particular organism from other organisms.
114. A surface assay device according to claim 32 that has a selective means to inhibit unwanted organisms.
115. A surface assay device according to claim 112 that has mannitol agar as a nutrient.
116. A surface assay device according to claim 112 that has MuellerHinton medium as a nutrient.
117. A surface assay device according to claim 113 that has phenol red as a differentiator.
118. A surface assay device according to claim 112 and claim 114 that has oxacillin screen agar as a nutrient and selective means.
119. A surface assay device that has NaCI as a selective means.
120. A surface assay device according to claim 83 which has detection medium of the following composition 6xgImL oxacillin plus 4% NaCI plus phenol red in mannitol agar nutrient.