WO2007032691A1

WO2007032691A1 - A microbiological growth device and a method of use

Info

Publication number: WO2007032691A1
Application number: PCT/NZ2006/000240
Authority: WO
Inventors: Gwyneth Anne Verkerk; Richard Mark Tiddy
Original assignee: Overnightest Limited
Priority date: 2005-09-16
Filing date: 2006-09-15
Publication date: 2007-03-22

Abstract

The invention is microbiological growth device having a receptacle which is used to house a quantity of microbiological growth media. The growth media is provided with at least one elongate recess having a length, or depth, greater than the minimum width of the recess. The elongate recess has a first end, or an open end, which is situated in or adjacent a free surface of the growth media, and a second end, or a closed end, which is situated within the growth media. Preferably the growth media is a selective growth media, and preferably the recess is a tapered recess and is capable of slightly restricting the supply of oxygen to its closed end. The invention is also a method of testing for bacteria or pathogens, where the results are presented by a colour change in the growth media.

Description

A Microbiological Growth Device and a Method of Use

FIELD OF THE INVENTION

This invention relates to a microbiological growth device and a method of use of the device, and in particular, but not exclusively to a microbiological growth device for field testing purposes.

BACKGROUND

Microbiological tests are commonly carried out in laboratories, and in many cases are carried out using a Petri dish and agar. Very small quantities of a sample to be tested are streaked thinly over the surface of the agar and the Petri dish is covered and incubated to promote the growth of populations of micro-organisms. The results can be analysed by a number of means, but typically the populations are analysed visually or with the aid of a microscope by an experienced microbiologist.

The entire process typically requires the use of specialist equipment and clean conditions, and can be time consuming. Also, great care must be taken to avoid contaminating or altering a sample as it is being sampled and transported to a testing laboratory.

In many field applications it is necessary to obtain test results quickly. If the tests could be carried out in the field it would be possible to eliminate the time that is used to transport a sample to a testing laboratory and to the time to report the results back to the field.

The testing of dairy cows for mastitis is such a case. Although mastitis can be caused by a wide range of micro-organisms, there is a relatively small number of primary pathogens that cause most infections. If a farmer could quickly identify the particular bacteria, or confirm whether an infected cow required medication or not, then significant gains could be made. The use of antibiotics could be avoided if they were not required, or the most appropriate antibiotic could be administered.

It has been estimated that approximately 20% of New Zealand's 5 million dairy cows are treated for mastitis every year. Mastitis is regarded as a key dairy health and milk quality issue in almost every dairying nation. The cost of mastitis to the New Zealand dairy farmer was estimated recently to be around $3600 per hundred cows per annum. Costs include reduced production, treatment, preventive measures, culling, milk discard and milk contamination by antibiotics.

In New Zealand the majority of mastitis is caused by Gram positive bacteria of the Streptococcus or Staphylococcus genus. Most infections respond to appropriate antibiotic therapy, however treatment selection is often undertaken on a "Best Guess" basis, as normal microbiological culture techniques are impractical and expensive.

Medical theory recommends that before undertaking any course of treatment the active infection is sampled and cultured in a diagnostic laboratory. Resulting sensitivity analysis can then allow the most appropriate and rational course of therapy. Additionally, the identity of the predominant bacteria can guide the animal health advisor in making preventative recommendations. For example, a high proportion of Streptococcus uberis indicates environmental infection.

In most cases where a culture is requested, a milk sample must travel from the farm to the veterinarian to the expert diagnostic laboratory and results be reported back to the farm via the veterinarian. This process can frequently take 3-5 working days. It is difficult for the farmer to find time to deliver the sample into town during the busy spring season, when most of the mastitis occurs.

Traditional milk bacteriology is slow and expensive, and as a result, only a very small percentage of mastitis cases are diagnosed with the help of laboratory testing. As a result, treatment of mastitis cases is undertaken with a drug that is "best guess". This could be based on past culture results or farmer experience. The full course of treatment takes 3-5 days, and is "all over" by the time the culture result is back.

The delay, or the logistic difficulties in obtaining test results, means that many cows are not treated correctly, sometimes the wrong antibiotics are used, and sometimes antibiotics are used when they do not need to be. This can delay the recovery process in the cow or cause milk to be unnecessarily discarded. The incorrect choice of drug could result in a failure to cure. This in turn could lead to longstanding chronic infection of the udder, which becomes difficult to cure. In this state, the cow may shed bacteria, putting her herdmates at risk of infection. She will also produce milk which is unacceptable for human consumption and may contaminate the herd vat. If she becomes an incurable case, she may have to be culled, despite being an otherwise productive cow.

Other situations, for example determining the cause of other infections in animals, or water quality testing, or even determining the cause of some infections in humans, can also be adversely affected by the difficulties or the time taken to obtain test results.

OBJECT

It is therefore an object of the present invention to provide a microbiological growth device and/or a method of use of the device which will at least go some way towards overcoming the above mentioned problems, or at least provide the public with a useful choice.

STATEMENTS OF THE INVENTION

Accordingly, in a first aspect, the invention may broadly be said to consist in a microbiological growth device, having a receptacle which is used to house a quantity of microbiological growth media wherein the growth media is provided with at least one elongate recess having a length, or depth, greater than the minimum width of the recess, the elongate recess having a first end, or an open end, which is situated in or adjacent a free surface of the growth media, and a second end, or a closed end, which is situated within the growth media.

Preferably the recess is tapered.

Preferably the tapered recess is broadest at the open end and is narrowest at the closed end.

Preferably the recess is so sized and shaped as to allow a flowable substance to flow substantially to the closed end of the recess but be narrow enough to provide a slight restriction to the flow of oxygen to the closed end, for example a slender or tapered recess. Preferably the tapered recess is a tapered recess that is approximately ten to thirty millimetres in depth having a "width at or adjacent its open end of approximately three to six millimetres and a width at or adjacent its closed end of less than two millimetres.

More preferably the tapered recess substantially tapers to, or towards, a point at its closed end.

Preferably the device further includes a closure means, for example a lid, cap or plug.

While the recess can be formed by cutting or otherwise removing a portion of growth media, or by at least partially joining two or more portions of growth media, preferably the recess is formed by the insertion of a former into the growth media before it has set.

Clearly the former can be separate from the device, however, optionally the former can be part of the device, for example part of the closure means.

Preferably the growth media is an agar type growth media.

Preferably the growth media is a selective growth media adapted to promote the growth of a limited range of microbes.

Preferably the growth media is adapted to provide a visual indicator to indicate the presence or population growth of a particular microbiological species or group of species.

While the visual indicator can require the use of ultra violet light to provide a visual indication, preferably the visual indicator does not require the use of ultra violet light to provide a visual indication.

In a second aspect, the invention may broadly be said to consist in a test kit incorporating at least one microbiological growth device substantially as specified herein.

Preferably the test kit further includes data recordal means, for example a surface on which data can be written, or tabs which can be punched to indicate the tag number of an animal, and/or the specific teat, from which a sample of milk has been extracted. Preferably the kit further includes visual representations which indicate the visual aspects of a positive or negative test result, for example coloured dots which show the colour that is associated with a particular result.

Preferably the test kit incorporates two or more growth devices that are connectable to form a kit capable of detecting more than one bacterial species.

In a third aspect, the invention may broadly be said to consist in a method of manufacture of a microbiological growth device including the steps of;

the preparation of a growth media solution,

pouring a quantity of the growth media solution into a receptacle, and

inserting a former into the growth media solution in the receptacle before the solution has set, and

allowing the solution to set.

Preferably the method of manufacture further includes the step of closing the receptacle.

Optionally the former is provided as part of a lid or closure device for the receptacle and the step of closing the receptacle causes the former to be inserted into the growth media.

Optionally the step of inserting a former into the growth media solution in the receptacle before the solution has set could be replaced by a step of cutting or pressing a recess in the growth media after it has set. In a fourth aspect the invention may broadly be said to consist of a method of testing for the occurrence of a particular bacteria or pathogenic micro-organism in a sample comprising the steps of:

depositing the sample in to a receptacle containing a predetermined growth media composition categorised by a particular colour;

incubating the receptacle and sample for a predetermined period;

determining whether a visible colour change has occurred;

according to the growth media composition, identifying the species of pathogenic micro-organisms in said sample.

Preferably the predetermined growth media composition is a selective growth media.

Preferably the selective growth media is part of a microbiological growth device substantially as specified herein.

Preferably the growth media is agar-based and includes ingredients relevant to the organisms preferably being cultured.

In a fifth aspect the invention may broadly be said to consist of a method of testing for the occurrence of mastitis in mammals comprising the steps of:

obtaining at least one sample of milk from a teat of the mammal to be tested;

incubating the receptacle and sample for a predetermined period;

determining whether a visible change has occurred;

classifying said mammal as mastitis affected or not; and according to the growth media composition, identifying the species of pathogenic micro-organisms in said sample.

Preferably the predetermined composition is a selective growth media.

Preferably the growth media is adapted to provide a visual indicator to indicate the presence or population growth of a particular mastitis bacteria.

Preferably the method involves the selective culturing of pathogenic mastitis from a list of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca and Enterobacter aerogenes.; Staphylococcus aureus, Staphylococcus chromogenes, Staphylococcus epidermidis, Staphylococcus hyicus, Staphylococcus simulans, Staphylococcus xylosus, Streptococcus agalactiae, Streptococcus uberis, and Streptococcus dysgalactiae Corynebacterium bovis, Psuedomonas and Mycoplasma species.

Preferably one species of pathogenic mastitis bacteria being selectively cultured is a contagious pathogen, Staphylococcus aureus.

Preferably one species of pathogenic mastitis bacteria being selectively cultured is an environmental pathogen, Streptococcus uberis.

In a sixth aspect, the invention may be said to consist of a growth media composition with which to perform one or more of the methods for testing for mastitis according to the principles disclosed in this specification.

The invention may also broadly be said to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of the parts, elements or features, and where specific integers are mentioned herein which have known equivalents, such equivalents are incorporated herein as if they were individually set forth. DESCRIPTION

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

FIGURE 1 is a cross sectional view of a first example of a microbiological growth device,

FIGURE 2 is a cross sectional view of a second example of a microbiological growth device,

FIGURE 3 is a perspective view showing a first example of a clip, the clip being suitable for holding three microbiological growth devices, and

FIGURE 4 is a perspective view showing a second example of a clip suitable for holding microbiological growth devices.

EXAMPLE ONE

With reference to Figure 1, a first example of a microbiological growth device (10) is shown having a receptacle (11) and a quantity of a microbiological growth media (13) which would typically be an agar product. The device further includes a cap (15) which can engage with the receptacle (11) to form a substantially air tight seal. Formed in the growth media (13) is a well or recess (17).

The receptacle (11) can be any suitable small container and is preferably made of a clear plastic or glass material, for example a microtube tube or similar product. While the receptacle can be any size, it has been found that a tube shaped receptacle that is about ten millimetres (mm) in diameter and about forty mm long is suitable. The receptacle (11) can comprise two or more chambers which may be formed as a single unit during the manufacturing process.

The recess (17) is elongate having a length, or depth, greater than the minimum width of the recess (17). The elongate recess (17) has a first end, or an open end, which is situated in or adjacent a free surface of the growth media (13), and a second end, or a closed end, which is situated within the growth media (13). In this example the recess (13) is a tapered recess, being narrower at its closed end (20) than at its open end. The tapered recess can taper to, or toward, a pint at its closed end.

The dimensions of a tapered recess (17) that has been found to be effective is a recess (17) with a depth (21) of approximately ten to thirty mm, or ideally about twenty mm, a width at the open end (23) of approximately three to six mm, or ideally about four mm, and a width (25) at the closed end (20) of less than two millimetres, or ideally less than one millimetre. The angle of taper is ideally between about five and twelve degrees. However, it is envisaged that other recess shapes could be used to achieve similar results.

Preferably the recess (17) is so sized and shaped as to allow a flowable substance, for example milk or water, to flow substantially to the closed end (20) of the recess (17) but be narrow enough to provide a slight restriction to the flow of oxygen to the closed end (20), for example a slender or tapered recess. The advantage of this slight restriction to the flow of oxygen is described below.

In use, a sample to be tested, for example a milk sample, can be placed in the receptacle (11) in contact with the growth media (13). In practice, milk can be squirted directly from the cleaned teat of a cow into the receptacle (11) minimising any contamination of the milk sample. The receptacle can be tapped to ensure that the milk has as far as possible toward the closed end (20) of the recess (17). Then the receptacle can be tipped over, or flicked, to remove excess milk, leaving a film of milk in the recess. Typically a small droplet of milk will remain in the bottom or closed end (20) of the recess (17).

The cap (15) can be used to seal the receptacle (11) and the device (10) can then be stored in a warm place, for example in an incubator, breast pocket or on a hot water cylinder, and after a period of time, typically 8 to 12 hours, the device can be inspected for the presence of bacterial populations.

The narrow tapered recess (17) as shown and described in this example is considered advantageous in that an oxygen tension gradient can be established during the growth of a microbiological population within the recess (17). The oxygen tension will be the least at the closed end (20) of the recess providing a suitable location for an anaerobic bacteria population to flourish. Aerobic bacteria will tend to flourish at the open end of the recess (17), and microaerophilic, facultative anaerobic or anaerobic, bacteria may be most likely to flourish at some point in between the closed end and the open end.

Ideally the growth media (13) is a selective growth media, for example a growth media which contains inhibitors that will inhibit the growth of many bacteria types that are either contaminants or are known to cause mastitis but which will allow a specific type of bacteria known to cause mastitis to flourish.

It is also an advantage if the growth media (13) contains a visual indicator, for example a coloured dye which can change colour due to the growth of a bacterial population, for example a dye which changes colour in response to a change in pH levels. This colour change feature, when used in combination with a selective growth media can provide a very simple indication of the presence of a particular bacteria type in the milk from a specific teat of a cow or other mammal.

Optionally, the visual indicator can require the use of ultra violet light to provide a visual indication.

EXAMPLE TWO

With reference to Figure 2, a second example of a microbiological growth device (40) is shown comprising a receptacle (41), a quantity of growth media (43) and a cap (45). Whilst many of the features of the device (40) are similar to the first example (10), the primary difference is the addition of a former (47) which forms a part of the cap (45).

The former (47) can be used to form a recess (49) in the growth media (43) as it sets. This can be an advantage in the manufacture of the device (40) since the growth media (43) can simply be poured into the receptacle while it is hot, the cap (45) with the former (47) can be installed, and when the growth media (43) has cooled the recess (49) will be formed.

In addition, the former (47) can further reduce the access of oxygen into the recess (49), which can assist in the growth of an anaerobic bacterial population within the recess (49). KIT SETS

In many cases more than one microbiological growth device will be used, for example where a number of micro-organisms may be known to cause a particular type of infection and where it is necessary to determine which bacteria prior to the administration of antibiotics. Two examples of clips which are designed to hold multiple devices are shown in Figures 3 and 4.

With reference to Figure 3, a first example of a clip (60) is shown having three bores (61) which can each retain a microbiological growth device (10) or (40). The clip (60) is also provided with a writing surface (63) which can for example be a rough surface on which a pencil will write clearly.

The kit can further include visual representations which indicate the visual aspects of a positive or negative test result, for example coloured dots which show the colour that the growth media can turn to indicate a particular result, for example the presence of the Streptococcus uberis bacteria in a milk sample.

With reference to Figure 4, a second example of a clip (80) is shown, the clip comprising a number of interlockable retainers (81), each retainer (81) having a bores (83) which can retain a microbiological growth device (10) or (40). A male portion (85) on each retainer (81) is designed to interlock with a corresponding female portion of an adjacent retainer (81).

A test kit for a typical New Zealand dairy farming environment would contain two microbiological growth devices, (10) or (40). One device would be aimed at identifying the Streptococcus uberis bacteria and another would be aimed at identifying the Staphylococcus aureus bacteria. Below are details of a typical test procedure for use in this situation. In other applications more than two growth devices (10) may be appropriate.

TESTING PROCEDURE

The present procedure provides essentially an overnight test which can be used to determine which micro-organism is present in mastitis milk. Testing may be undertaken on an individual animal and even on an individual udder quarter from which the milk was obtained (particularly useful where the infection is recent and the mastitis may be subclinical and be localised in one quarter of the udder). The test of this described embodiment is designed to determine the difference between mastitis caused by the presence of Streptococcus uberis and/or Staphylococcus aureus. The test can be used to confirm a choice of treatment - including use of the right drug regime, to enable selective treatment for high cell count cows, and also frozen milk samples to be used in the test.

The method is based on pH colour change in the selective growth media. For example, where Streptococcus uberis is present, there is a colour change in the media from purple to yellow. When Staphylococcus aureus is present there is a colour change in the media from red/orange to rich yellow. If no change is recorded in the colour of the media this provides an indicator of various options, such as the presence of other rare infections, such as E.coli, or may be a false negative where antibiotics may have been administered to the animal prior to testing and is preventing bacterial growth in the test sample (however, subsequent testing may then confirm the result in such instances).

The steps involved with one embodiment of the procedure are:

1. Take a milk sample.

2. Use sterile pipette to instill 2-3 drops of the milk in to a recess or well in the centre of the selective media already present in a receptacle.

3. Flick the receptacle downwards once, to ensure the milk is dispersed over the sides of the recess or well.

4. Tip excess milk out of the receptacle.

5. Close the receptacle.

6. Incubate the sample in a suitable warm place, for example on a water heater or in a pocket of a garment being worn. A suitable incubation period may be overnight or between milkings.

7. Read the colour change after about 8 -24 hours.

Alternatively, the procedure may use fresh milk, and may be applied to the receptacle directly from the teat, being careful to ensure that no contamination is introduced from the external surface of the teat. The milk sample may be obtained by any usual and appropriate means. An example of an alternative procedure or method of testing for the occurrence of mastitis in mammals is as follows; obtain at least one sample of milk from a teat of the mammal to be tested,;

deposit the sample into a receptacle containing a predetermined growth media composition categorised by a particular colour, for example by squirting milk directly from the teat;

incubate the receptacle and sample for a predetermined period;

determine whether a visible change has occurred;

classify said mammal as mastitis affected or not; and

according to the growth media composition, identify the species of pathogenic microorganisms in said sample.

These procedures usually provide results within 8 to 24 hours of the test being undertaken.

It is relevant to the procedure that the milk sample be distributed within the recess or well of the agar media in the test tube. In addition, it is preferable not to have too much milk in the receptacle as only a fine film of milk is required, although a little milk which may remain in the base of the recess is acceptable.

Table I. Interpretation of a typical test.

The following table is based on a kit having two tubes, a first tube with a selective growth media designed to support the growth of streptococcus uberis bacteria and having a pH sensitive purple dye which changes to yellow to show a positive result, and a second tube with a selective growth media designed to support the growth of staphylococcus aureus bacteria and having a pH sensitive red dye which changes to yellow to show a positive result.

The test results provide information on the individual cow and can provide insight into the total herd status. By periodically recording the results monitoring of herd levels is possible as is the investigation of possible causes and early treatment when results differ from one test to the next. VARIATIONS

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

In the above examples the selective growth media can be growth compounds such as animal, plant or microbial extracts, blood plasma or sera, peptones, caseins, carbohydrates, salts, amino acids, nucleic acids, with additives such as esculin , haemin, vitamins, lipids and fatty acids, combined with a suitable pH and agar. In addition to these general growth compounds the media can be supplemented with indicators, for example pH or oxidation-reduction indicators, together with inhibitory compounds, for example antibiotics, chemicals or dyes, that selectively allow the growth of the bacteria of interest, whilst at the same time, either eliminate or suppress unwanted contaminating micro-organisms.

It is envisaged that the device or the method can be used to identify the presence of a range of pathogenic mastitis for example; Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca and Enterobacter aerogenes, Staphylococcus aureus, Staphylococcus chromogenes,

Staphylococcus epidermidis, Staphylococcus hyicus, Staphylococcus simulans, Staphylococcus xylosus, Streptococcus agalactiae, Streptococcus uberis, and Streptococcus dysgalactiae Corynebacterium bovis, Psuedomonas and Mycoplasma species.

In addition, the use of highly selective media has many applications in diagnostic microbiology, particularly where the differential diagnosis is established and limited to only a relatively few species of micro-organisms (bacteria, archae, protozoa, fungi, yeasts, insects and parasites). Thus example applications could be in animal mastitis (e.g. cattle, goats and sheep) where the number of recognized primary pathogens (Streptococci, coliforms and Staphylococcus aureus ) is relatively small. Other veterinary applications may be in the diagnosis of skin infections, ear infections, and in the public health arena for testing recreational or potable water. There are other numerous applications in human microbiology such as the diagnosis of impetigo or pyrogenic sore throats. It is also possible that the system could be used to determine sensitivities of pathogens to therapeutic products to increase the likelihood that treatment will be successful.

In these other applications, the method of testing for the occurrence of a particular bacteria or pathogenic micro-organism in a sample can comprise the steps of:

depositing the sample into a receptacle containing a predetermined growth media composition categorised by a particular colour;

incubating the receptacle and sample for a predetermined period;

determining whether a visible colour change has occurred;

Preferably the predetermined growth media composition is a selective growth media. Preferably the selective growth media is part of a microbiological growth device substantially as described herein. Preferably the growth media is agar-based and includes ingredients relevant to the organisms preferably being cultured. Preferably the growth media is adapted to provide a visual indicator to indicate the presence or population growth of a particular microbiological species or group of species. DEFINITIONS

Throughout this specification the word "comprise" and variations of that word, such as "comprises" and "comprising", are not intended to exclude other additives, components, integers or steps.

ADVANTAGES

Using a selective culture medium in a small tube and a pH indicator, mastitis micro-organisms can be grown in the tube and cause a colour change making it possible to achieve a relatively quick diagnosis by a relatively inexperienced operator. The tube simply requires a small amount of milk to be added, then can be kept in a warm pocket, or left on a water heater overnight. The colour change is will usually be evident 8-12 hours later.

In addition to use of the device by farmers and vets, drug companies may see potential in the device for promoting responsible drug use and corporate responsibility.

Sometimes the farmer is not certain whether to treat or not, as many cases of mastitis may be in a process of "self cure". This is particularly true in apparently mild cases. Testing with this device may result in not having to treat the cow potentially avoiding the costs of treatment and the cost of any discarded milk, the risk of antibiotic contamination of the milk and/or the inconvenience of running the cow separately from the herd.

Without the aid of a convenient test, in some cases a farmer may start treatment of a cow, and then, when the treatment fails, may attempt to culture the "difficult" bug. Unfortunately, the exercise is normally unrewarding, as the initial treatment may have decreased the bacterial count sufficiently that routine culture will not pick up the infection. The result is frequently a frustrating "false negative". Routinely culturing with the device (10) or (40), before treatment of any cow suspected of having mastitis, can help avoid this scenario.

The testing of milk using the device (10) or (40) can also help in herd management troubleshooting, as the type of bacteria grown can point to certain factors, such as milking machines, as being the major players in the development of the herd problem. Thus milk culture results for a herd can help to solve problems and to prevent mastitis in the future.

Claims

1. A microbiological growth device having a receptacle which is used to house a quantity of microbiological growth media wherein the growth media is provided with at least one elongate recess having a length, or depth, greater than the minimum width of the recess, the elongate recess having a first end, or an open end, which is situated in or adjacent a free surface of the growth media, and a second end, or a closed end, which is situated within the growth media.

2. A microbiological growth device as claimed in claim 1, wherein the recess is tapered, the tapered being broadest at the open end and narrowest at the closed end.

3. A microbiological growth device as claimed in any of claims 1 or 2, wherein the recess is so sized and shaped as to allow a flowable substance to flow substantially to the closed end of the recess but be narrow enough to provide a slight restriction to the flow of oxygen to the closed end, for example a slender or tapered recess.

4. A microbiological growth device as claimed in any of claims 2 or 3, wherein the tapered recess is a tapered recess that is approximately ten to thirty millimetres in depth having a width at or adjacent its open end of approximately three to six millimetres and a width at or adjacent its closed end of less than two millimetres.

5. A microbiological growth device as claimed in any of claims 2 to 4, wherein the tapered recess substantially tapers to, or towards, a point at its closed end.

6. A microbiological growth device as claimed in any preceding claim, wherein the device further includes a closure means, for example a lid, cap or plug.

7. A microbiological growth device as claimed in any preceding claim, wherein the growth media is a selective growth media adapted to promote the growth of a limited range of microbes.

8. A microbiological growth device as claimed in any preceding claim, wherein the growth media is adapted to provide a visual indicator to indicate the presence or population growth of a particular microbiological species or group of species.

9. A test kit incorporating at least one microbiological growth device substantially as claimed herein.

10. A method of manufacture of a microbiological growth device including the steps of;

the preparation of a growth media solution,

pouring a quantity of the growth media solution into a receptacle, and

allowing the solution to set.

11. A method of testing for the occurrence of a particular bacteria or pathogenic micro- organism in a sample comprising the steps of:

incubating the receptacle and sample for a predetermined period;

determining whether a visible colour change has occurred;

12. A method of testing as claimed in claim 11, wherein the predetermined growth media composition is a selective growth media.

13. A method of testing as claimed in any one of claims 11 or 12, wherein the selective growth media is part of a microbiological growth device substantially as claimed herein.

14. A method of testing as claimed in any one of claims 11 to 13, wherein the growth media is adapted to provide a visual indicator to indicate the presence or population growth of a particular microbiological species or group of species.

15. A method of testing for the occurrence of mastitis in mammals comprising the steps of:

obtaining at least one sample of milk from a teat of the mammal to be tested;

incubating the receptacle and sample for a predetermined period;

determining whether a visible change has occurred;

classifying said mammal as mastitis affected or not; and

16. A method of testing as claimed in claim 15, wherein the predetermined composition is a selective growth media.

17. A method of testing as claimed in claim 16, wherein the selective growth media is part of a microbiological growth device substantially as claimed herein.

18. A method of testing as claimed in any one of claims 15 or 17, wherein the growth media is agar-based and includes ingredients relevant to the organisms preferably being cultured.

19. A method of testing as claimed in any one of claims 15 to 18, wherein the growth media is adapted to provide a visual indicator to indicate the presence or population growth of a particular mastitis bacteria.