Method for detecting, identifying and enumerating micro-organisms in a porous support dry-impregnated wit11 a dehydrated reaction medium 5 The present invention relates generally to tlie field of niicrobiological analysis. More particularly, it relates to a method for the detection, identification and/or enunleration of microorganisn~s in a porous support dry-imnpregnated throughout its thickness by a dehydrated reaction medium. 10 In the fields of clinical diagnostics and industrial ~nicrobiological control, foodprocessing, phar~naceuticals or cosmetics, gelled culture media in petri dishes, no st frequently agar media, have been an indispensable tool in the detection and identification of pathogenic microorganis~nss ince the end of the 19"' century. 15 Several products have been made commercially available to replace a petri dish culture medium. One of these, the petrifilngM system, comprising rehydratable nutrients, is very widely used. Another system developed by Nissui Pharmaceutical, Compact ~ r y ' ~a,ls o consists of a dehydrated medium. These culture media have the advantage that they can be preserved for longer than a ready-to-use agar culture medium. They 20 lnay also, as is the case for ~etrifilm'~b, e small in size and thus take up a small amount of incubation space. Thus, broadly speaking, there are two \vajrs to obtain a rehydratable culture nledium: the first consists in placing the culture nledium in liquid for111 in the support, then drying 25 the whole thing, and tlie second consists in adhering the culture nledium in dehydrated fornl to a support, so as to immediately obtain a rehydratable culture medium. The first method, namely obtaining rehydratable nutritive media manufactured including a phase for wet impregnation of the nutrients, has been the subject of several 30 patent applications. Thus, patent applicatiotl CN102337324 describes a method in which the nutritive broth is mixed \vitIi a chemical coniponent which evaporates rapidly. Document W02005/061013 describes a marker dissolved in a solve~a~ntd deposited on an absorbent layer, so as to detcct vaginitis. Mole recently, -. patellt application US20130089887 describes a support, namely a thin membrane inipregnated with clxomogenic andlor fluorogenic substrates dissolved in a solvent, placed in contact with an agar medium. 5 Nonetheless, this method for dissolving in water or in a solvent has a negative impact on the length of time for which the rehydratable culture medium can be preserved. Indeed, placing certain fsagile products such as enzynies or enzy~iiatic or metabolic substrates or antibiotics in suspension may have a severe impact on their overall 10 stability. The heating required to dry the culture medium may also denature, and render ineffective, the heat-sensitive components of the reaction medium. This method in aqueous phase also does not make it possible to control and vary the location of the reaction medium andlor the various additives required for bacterial visualization. 15 In order to overcome the drawbacks of the culture media obtained by this method, the second method proposes placing the nutritive powder directly onto the support without a prior phase of'dissci"tvingsaid.powder. Thus, 3M propose a dehydrated nutritive medium coated with adhesive and placed on a film without having gone tlxougl~a prior phase of dissolving the medium. This device 20 consists of two parts, a bottom film and a top film, covered at their surface by certain components of the dehydrated culture medium. At the time of the analysis, the satnple is placed between these two films. This device and the associated detection method, as described in application WO 2009/082667, have several drawbacks. 25 First of all,-this-device requires,. for its manufacture, a step of adhering the dehydrated nutrients to the films which have bad to be coated with adhesive beforehand. Following this, the culhtre medium cannot de facto form a three-dimensional strt~cture with ; variable height and layered concentrations, since it is adhered to a film. Only one small superficial layer of medium is therefore available. The volume of the liquid sample 30 required for tnicrobiological analysis may therefore not exceed 1 or 2 ml, which i~npacts the tlxeshold for detection sensitivity. Then, the packaging of the petrifilmTM requires the manufacturing of the bottom film and the top film together. It also does not make it possible to have several difrerent culture media on the same device. Morcover, this device has limited applications and cannot, for example, be used for taking swabs or as a dressing. Finally, tlie petrifilniT" necessarily requires the input of an external operator providing the aqueous sample. 5 On the other hand, in an earlier patent application FR1257047, the applicant proposcs a nletliod for isolation, from a sample to be analyzed, on a culture medium that is rehydratable in sihc, which makes it possible to obtain isolated colonies. This rehydratable medium is covered with a membrane enabling colonies to be isolated. 10 Thus, tlie culture tnedium retnains sterile and the colonies develop on the membrane which is just above said medium. However, isolation of colonies, on an agar or non-agar support, is sometimes seen as a constraint and is often incoinpatible with experiments carried out outside the laboratory and/or by people having little knowledge and know-how in the field of microbiology. 15 In light of all the problems laid out above, the present invention proposes a novel method for dete&m;fdt!n'Yification arid enumeration of microorganisms liable to be contained in a sample. 20 Thus, one aim of the present invention is to provide a device comprising a dehydrated medium improving detection sensitivity. Another aim of the present invention is to provide a method for detection, identification and enumeration of microorganisms without having to rely on isolation. 25 -. Another aim of the present invet~tion is to provide a device and a method enabling multi-detection, and thus to obtain, from tlie same sample to be analyzed and without carrying out isolation, isolated, identifiable and countable cultures on different reaction media present on the same device. 30 One aim of the invention is also to provide a pal-titularly flexible device and method. The reaction ~nediunml ay be a more or less complex medium, which is chomogenic, for example, or may be very simple, that is to say solely containing a limited number of substrates (antibiotics, ~netabolics ubstrates, etc.). The device and the mnethod may also have very varied modes of use, such as a swab, or an absorbent medium for visualizing ~iiicrobiacl ontaminations in dressings, sanitary pads or food packaging. 5 Another aim of the present invention is to provide a device wliich can be used by people having little know-how in microbiology. Thus, the device may be rehydrated in one go by the operator at the time of the analysis of the sample. Rehydration may also be carried out in sit11 without the input of the operator, especially if the sample to be tested 10 is placed in proximity to the rehydratable reaction medium, allowing its gradual rehydration. The sample to be analyzed may for example be an exudative \vouud or a piece of meat and may produce a liquid liable to contain the microorganisms to be detected. 15 Another aim of the present invention is to provide a device which itself serves for the collection of the sample, such as a swab. , ,.. One aim of the present invention is to provide a device, the production and sale of which are facilitated by the fact that the porous support dry-impregnated by a reaction 20 medium is produced independently of its packaging. Another aim of the present invention is to provide a device in which a concentration gradient of the reaction substrates is created, thereby enabling the amount of these substrates to be limited, and the production cost of the device to be limited. 25 Other aims will become apparent upon reading the present application. The present invention therefore aims to achieve all or some of the abovementioned aims. 30 Consequently, a subject of the present invention is a method for the detection and/or identification and/or enumeration of at least one target microorgat~ismin a sample liable to contain it, co~nprisingth e following steps: (a) providing a device for the detection and/or identification and/or enumeration of microorganisms comprising a porous support conlprising reaction mediunl powder tlxougl~out its thickness, said porous support having been d~yitnpregnated throughout its thickness by a dehydrated reaction mediuni, 5 (b) placing a sample in contact with the porous support, (c) incubating the device, (d) detecting andlor identifying and/or enumerating the colony or colonies of microorganistns within the porous support, when the microorganisn~ss ought are present in the sanlple. 10 According to the invention, the device is dry-impregnated thoughout its thickness by a dehydrated reaction medium. The incorporation of pulverulent materials into porous supports may be carried out according to at least four techniques: - use of a vacuum pump as described in patent US 5,213,843; 15 - mechanically vibrating the potous support itself, on which the powder has been placed, by any vibrating system, the vibrations making it possible to cause the powder to penetrate more or'less deeply, - use of an electrostatic field; - ultrasonic vibration, sitnultaneous to the application of the powder, using an 20 ultrasound generator which causes a sonotrode to vibrate, as described in patent application FR 2866578. When the porous product passes tinder the sonotrode, the action of the latter vibrates the powder pasticlcs, and they then penetrate into the cavities of the porous substance. 25 Preferentially, -the method for manufacturing the porous support dry-impregnated throughout its thickness comprises a step of vibrating the powder particles by means of an electric field. Preferentially, this is an alternating electric field. Patent EP 1.028.836 describes the impregnation of textiles (nonwoven, woven, etc.) by applying an alternating electric field between two systems of electrodes, between which the powvder- 30 covered textile is located. The powder particles, which become electrically charged, sta1.t to vibrate at the frequency of the alternating field. Thus, surprisingly, this teclmiqae may be used to dly-impregnate a porous suppost with a dehydrated reaction mncdium. The n~ovenlents of the particles therefore enable their penetration into the pores of the support. The particles have penetrated tlie porous support at depth, tl~sougl~ootuhte thickness of the support. Thus, the zones of the support that are impregnated with nlediunl are impregnated 5 throughout tlie thickness of the support, since the powder bas passed through the thickness of the porous support. Thus, at least all or some of the porous support comprises a reaction medium in powder form tl~roughouti ts thickness, with some zones on the support nonetheless being able to be devoid of any medium, such as for example the perimeter of the support. 10 The degree of impregnation of the particles though the thickness of the support rnay be controlled, for example homogeneously, in a localized malltier or as a gradient, depending on the characteristics of the materials present (s~~pposatsn d powders), but also the characteristics of the method enlployed (intensity of the electric field, treatment 15 time, fsequency, etc.). The support may be impregnated sequentially over time, which enables better impregnation. Thus; 'the impregnation with gelling agent may take place before the impregnation with reaction medium. 20 Dry inlpregnation of a dehydrated mediunl throughout the thickness of a porous support docs not require the use of water and enables the location of the particles to be controlled. Moreover, it enables flexibility though the thickness of the impregnated layer by enabling different zones to be defined through the thich~ess, which are in different amounts and arc of different natures. 25 Advantageously, .a-.concentration gradient of tlie reaction substrates is created in tlie porous support, thereby making it possible to limit the amoutlt of these substrates arld to limit the production cost of the device. It lnay also be chosen to have a porous support comprising one type of substrate distributed ho~nogcneouslp and another type. of substrate distributed in a gradient. Advantageoosly, the support is impregnated 30 thoughout its thickness by a nutritive medium and superficially by chomoge~lic substsates. In another embodiment, the substrates arc encapsulated, enabling their sequential release after incubation of the device. Thus, this embodiment has the advantage of limiting the use of the substrates by avoiding their dilution in the nutritional nledium during rehydration of the medium. Similarly, a selective agent such as an antibiotic nlay also be encapsulated. This embodinlent is particularly advantageous since it rnakes it possible to postpone placing 5 the contents (comprising a small amount of target microorganisms, if the latter are present) in contact with the selective agent intended to orient the growth of the microorganistns toward that of the rilicroorganisms being sought. Thus, the n~icroorganismsin the microbial stress phase are not directly placed in contact with the selective agent, the latter carrying a risk, at this stage, of either slowing down the 10 growth of said microorganisn~sa nd hence increasing the time needed for analysis, or of completely inhibiting the growth of said microorganisn~s and thus preventing their detection/identification. This is because the target microorganisn~s are said to be "stressed" when they are present in the sample to be analyzed. The microorganisms (including the target microorganisms) need a certain amount of time to adapt to the 15 conditions existing within the porous support. In their "stressed" state, the target microorgat~isms are particularly sensitive, especially to the presence of selective agents such as antibiotics. Thus, the porous support may comprise different reaction media. These reaction media 20 are located in different zones of the support. These zones may co~~espontod veitical zones and therefore to the thickness of the support, andlor correspond to horizontal zones of the support. The porous support may therefore have, in one zone, several reaction media, such as for example a culture medium and a visualization medium. The device may also have one or more reaction media arranged in different zones of one or 25 more porous suppoltsj. each of these zones having reaction medium distributed throughout the thickness of the support. In practice, several parameters may influence carrying out this method, ;such as, principally: 30 - the texture of the network of fibers or filaments, or generally speaking of the porous support used; - the pl~ysicochemicapl roperties of the powders, such as the nature or the pa~ticle size of the powder; - the duration of the treatment, tllc intensity of tile electric field and also the frequency of the electric field. 5 It will therefore be necessary to adapt these parameters so as to enable satisfactory dry impregnation of the reaction medium in the porous support. Preferentially, the amount of reaction medium, in powder for~n, impregnated in the porous support is between 0.01 g/cmn3 and 0.1 g/cmn3, preferably between 0.02 g/c1113 and 0.09 g/cm3, more preferentially between 0.03 g/cm3 and 0.06 g/cm3. 10 Preferentially, when the reaction medium comprises a culture mediutn and optionally a visualizatioll medium, the amount of impregnated reaction tneditun, in powder form, is between 0.01 &rn3 and 0.09 g/cm3, more preferentially between 0.03 g/cm3 and 0.06 g/cm3. Thus, an advantage of the present invention is to enable optimized growth, especially due to the excess amount of culture medium which thereby alleviates 15 of nutsient competition among the ~nicroorganisms. Preferentially, when the reaction medium comprises a visualization medium without culture medium,lfre-amaunt Ofimpregnated reaction medium, in powder form, is much lower and is between 0.10 mg/cm3 and 10 mg/cm3. 20 According to the invention, the porous suppost is placed in contact with the sample. In one embodiment of the invention, the sa~npleis aqueous and will enable rehydration of the reaction medium contained in the porous support. 25 According to another embodiment, a suitable volume of liquid is added to the sample andlor to the porous support in order to rehydrate the reaction medium, when the sample is not aqueous or is insufficiently aqueous. In practice, those skilled it1 the a ~wt i ll choose the suitable volume of liquid or of 30 aqueous sample as a function of its viscosity and of the diameter of the porous support, so as to rehydrate the medium and enable the growth of the microorganisms. Advantageously, the rehydration of tlie porous support requires a volume of liquid or of aqueous satnple of greater than 2 1111, preferentially greater than 3 ml, even Inore preferentially greater than 4 till, which makes it possible to improve detection sensitivity when the microorganisms are at a low concentration in the sample. 5 According to the present invention, the sample may conlprise a prior step of preparation, concentration or dilution of the sample. According to the invention, rehydration of the support rnay be carried out with or 10 without operator intervention. The aqueous sample may be added manually by means of a pipette or auton~aticallyi nto the device. It may also be contained in at least one reservoir integrated into the device and/or in channels enabling rehydration of the porous support. It then spreads through the support simply by pressing on the reservoir. 15 Advantageously, the sample is placed in contact with the porous support by placing it under the porous support. Thus, rehydration takes place via the lower and/or lateral portion, prefei%%iy -.uix-Yhe. lower portion. This operating procedure enables homogeneous hydration of the whole porous support and especially avoids nutrients and/or substrates from being drawn, by the liquid or the aqueous sample, into the lower 20 portion of the device. Advantageously, this operating procedure enables the method according to the invention to be carried out in space by solving the problem linked to the absence of gravity for the sample and/or the liquid. In one embodiment, there is no human intervention arid the aqueous sample originates directly from a zone producing the liquid to be tested. This nlap be, for example, an 25 exudative wound or foodstt~ffsw hich release liquids during their storage. The sample, by its very nature, will release some of its constituent liquids which will, over tirne, soak into the porous support. The zone producing the sanlple to be tested may also be a perineal zone of hutnans or animals excreting urine. The porous support is then placed in proximity to this zone and is impregnated gradually by the aqaeous sanlple produced. 30 In another embodiment, tlie satnple is placed in contact with the porous support by taking the sample using the porous support. The porous support is thus used as a swab and the operator must place the latter in a tube containing a suitable atnount of liquid if the sample is not aqueous or is insufficiently aqueous. The device is subsequently incubated in situ (in the case of dressings, sanitary pads, 5 etc.) or in an incubator for a sufficient length of time to enable the detection of tnicrobial colonies within the porous support. According to one preferred embodiment, the method according to the invention is a detection method which may be carried out by visual or optical reading of the porous support. 10 Tlie invention also relates to a device comprising a porous support dry-impregnated throughout its thickness with a dehydrated reaction mediuni enabling the visualization of colonies of microorganisms within said support, said porous support being calendered. 15 The porous support has been dry-impregnated throughout its thickness, that is to say that when a reaction medium is present at a location of the support, it is present in this zone thougho~-thetMcknesosf the support. The porous support has undergone a calendering operation. Calendering, though the pressure and heating temperature generated, enables. stable maintenance and retention 20 over time of the dehydrated reaction tnediutn in the porous support by ensuring tlie retention of the different elements such as nutritive elements in the porous support. It also makes it possible to obtain a completely smooth and planar upper surface of tlie porous support, Preferentially, calendering is carried out at a temperature higher than room temperature, 25 preferentially ata 300 colonies 49/57/61 2 300 colonies 0 0 453 The porotis supports \vere impregnated by the following tnedia: - MH2 (Muller Hinton 2) + xanthan alliance gum pharnia - MH2 + xanthan alliance gum phamla + 1.5 mgfl ciprofloxacin - MH2 + xattthan alliance gum pharma 5 - CPS3 + xanthan alliance gum pharma - CPS3 + xanthau alliance gun1 pharma + 1.5 mg/l ciprofloxacin Strains tested: - Protells nrirnbilis API 8803099, ADM AP3, MIC: 0.125 10 - Protetis ~nirribilisA PI 8803080, ADM JS10, MIC: 0.25 - Protetis nrirubilis API 9406037, bioM6rieux collection, MIC: 4 - Prote~cs~ ~~ilgaArPiIs 8803017, ADM CQ11, MIC: 0.125 - Psezidomonus uerrigiriosn API 9405061, bioM6rieux collection, MIC: 0.125 - Psetidor~ronnns erriginosn AP17509005, ATCC 25853, MIC: 0.5 15 - Pseridorirorias aerrigi~iosuA PI 941 0075, MIC: 16 - Pser~dornonusu erugirioso API 9405063, MIC: 4 Method: To produce the agar media, a liter of water is added to the test specimen of the d ~ y 20 mediunn, i.e. 38.3 g for Chro~nlD CPS3 and 41.57 g for the Muller Hinton 2 medium. The dry medium is then dissolved with magnetic stirring, brought to the boil then sterilized by autoelaving. After cooling the agar tnediutn to 55OC, the ciprofloxacin sterilized by filtration is added to the agar medium at a concentration of 1.5 mg/l. To carry out impregnation according to the present itiverltion of the dry media MH2 and 25 Cham ID CPS3, a -test specimen of the dry medium corresponding to the manufacture of one liter of medium is taken, i.e. 26 g for Clxom ID CPS3 and 26.07 g for the Muller Hinton 2 medium, to which test specimen xanthan (20 g) and, if appropriate, ciprofloxacin (1.5 g) are added. The whole thing is theit mixed together in a turbulaB. The porous supports are then impregnated with the culture nmedia powders as described 30 above and sterilized by gaulnla radiation between 10 and 17 kGy. Conclusion In this example, the Muller Hinton and ChrornID CPS3 agar niedia with or without 5 1.5 gll ciprofloxacin were compared to the porous supports acco~ding to the present invention impregnated with the same lnedia with or without 1.5 gll ciprofloxacin for three strains of Protells ntirrrbilis, one strain of Proferrs vlilg(iris and four strains of Psezrdorrtor~rrsc rerrtgil~osaA. ll these strains had an MIC around the value of 1.5 mg/l of ciprofloxacin. The strains with an MIC of less than 1.5 mg/l (P~.ole~~rs~ i ~ a b iAl iPsI: 10 8803099, Protetis r~rirabilis: API 8803080, Proterrs 1vr1gcn.i~: API 8803017, Pselrdorrtonas rrerlrgiliosa: AP1 9405061, Psetrdor~tonos rrerllginosa: API 7509005) do not grow on MH2 agar media + substrates + ciprofloxacin (1.5 mg/l) and ChromID CPS3 wit11 ciprofloxacin added (1.5 mg/l). Similarly, these "ciprofloxacin-sensitive" strains, for an MIC of 1.5 n~g/ld, o not grow either on the porous supports impregnated 15 with ChromID CPS3 media and MH2 + substrate in the presence of 1.5 mg/l ciprofloxacin. The results obtained on agar media and on porous supports impregnated according to the present invention are therefore consistent with one another. All these strains grow on MH2 + substrate or Cl~om1DC PS3 agar media and on porous supports impregnated by MH2 + substrate and ChromID CPS3 media. 20 The strains with an MIC of greater than 1.5 mgll (Proferrs mirobilis: API 9406037, Pseudor~toliusa ertrginoso: API 9410075, Psetrdornonas aerlrgilzosa: M I9 40506) grow on all the agar or impregnated media, with or without ciprofloxacin (1.5 dl). These results confirm that it is possible to produce culture lnedia according to the present invention containing small amounts of active agents such as chromogenic substrates or 25 antibiotics. Claims 1 A method for the detection and/or identification and/or ellu~nerationo f at least 5 one target microorganism in a sanlple liable to contain it, comprising the following steps: (a) providing a device for the detection and/or identification and/or enumeration of tl~icroorganisms comprising a porous support comprising reaction medium powder throughout its thickness, said porous support having been 10 dry-impregnated throughout its thickness by a dehydrated reaction medium, (b) placing a sample in contact with the porous support, (c) incubating the device, (d) detecting andlor identifying and/or enumerating the colony or colonies of microorga~lisn~wsi thin the porous support, when the microorganisms sought are present 15 in the sample. 2 The method as claimed in claim 1, comprising a prior step of preparation, dilution or concentration of the sample. 20 3 The method as claimed in either one of claims 1 and 2, wherein step b) is carried out by placing the sample under the porous support. 4 The method as claimed in either one of claims I and 2, wherein step b) is carried out by taking the sanlple using the porous snpport. 25 5 The method as claimed in any one of the preceding claims, wherein, when the sample is not aqueous or is insufliciently aqueous, a suitable volume of liquid is added to the sample andor to the porous support in order to rehydrate the reaction medium. 30 6 A device comprising a porous support comprising at least one dehydrated reaction medium in powder form distributed throughout the thickness of the porous support, said porous support having a thickness of between 0.5 and 2 mm and being calendered. 7 The device as claimed in clairn 6, characterized in that at least one reaction medium in po~vder form is homogeneously distributed through the thich~ess of the porous support. 5 8 Tlie device as claimed in claim 6, characterized in that at least one reaction medium in powder form is distributed in a graduated maluler through the thickness of the porous support. 10 9 The device as claimed in claim 6, characterized in that it comprises at least two different reaction media in powder form distributed in at least two layers, said support comprising, at a given point through the thickness, one or the other culture medium. 10 The device as claimed in any one of tlie preceding claims, wherein the reaction 15 medium is a visualization medium and/or a culture medium. 11 The device as claimed in any one of the preceding claims, wherein tlie reaction medium comprises at least one gelling agent, the amount of which is between 1 mg/cm2 and 2 mg/cm2. 20 12 The device as claimed in any one of the preceding claims, wherein the amou~iot f reaction medium impregnated in the porous support is between 0.10 tng/cm3 and 0.1 g/c~n3p, referably between 0.01 g/cm3 and 0.09 g/cmn3. 25 13 The device comprising a plurality of porous suppo~tsa s described in claims 6 to 12. 14 The device as claimed in any one of claims 6 to 13, \vherein the porous'support is integrated into a dressing, a bandage, a sanitary pad or an item of food packaging. 30 15 The device as claimed in any one of claims 6 to 13 comprising a rod, at the end of which said porous support is fixed. 16 The device as claimed in any one of clai~ns6 to 15, characterized in that the medium is a culture medium for detecting methicillin-resistant Staphylococci. 17 The use of a device as claimed in any one of claims 6 to 16 for detecting andfor 5 identifying andlor enumerating at least one target microorganism in a sample liable to contain it. 18 . The use of a device as claimed in claim 14 as a dressing. 10 19 Tlie use of a device as claimed in claim 14 as a sanitary pad. 20 The use of a device as claimed in claim 14 as packaging k r foodstuffs. 2 1 The use of a device as claimed in claim 15 as a swab.