Abstract:
The present disclosure relates to an assembly formed from a planar rigid filtration membrane and generally flat plate for accommodating and supporting this membrane, to activate and/or reveal immobilized contaminants on the membrane, the support plate comprising a holding and immobilization device cooperating with a periphery of the membrane, wherein the device comprises at least one non-deformable member that projects from the general plane of the plate and at least one stop tab, substantially perpendicular to the plane, which is extended by a holding appendage substantially parallel to the plane, so that the membrane can be engaged with the member only through a first movement of the membrane substantially parallel to the plane of the support followed by a second movement substantially perpendicular to the plane.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a National Phase Entry of International Application No. PCT/EP2010/056567, filed on May 12, 2010, which claims priority to French Patent Application Serial No. 0953120, filed on May 12, 2009, both of which are incorporated by reference herein. 
     
    
     BACKGROUND AND SUMMARY 
       [0002]    The present invention is situated in the field of equipment for the microbiological testing of substances in the liquid phase. 
         [0003]    Qualitative or even quantitative analysis of the presence of contaminants such as microorganisms is necessary for performing sterility tests on fluids. Thus the detection and analysis of particles, living or otherwise, contained in liquid or gaseous fluids, food, pharmaceutical, biological, cosmetic or health products, as well as the monitoring of fermentation processes, in general includes a step of depositing particles on a substrate and the optical analysis, for example by scanning, of the surface of this substrate. 
         [0004]    The present applicant has developed a technique according to which the particles are retained on a filtration membrane, following which the latter is put in contact with a material able to react with the contaminated particles in order to mark them, so that the marking product reacts with the enzymatic activity of the contaminant, in order to create a fluorescent signal. It then suffices to carry out an analysis, in particular by laser excitation of the membrane, in order to check whether contaminants are present and in what number. Such a technique has widely supplanted the one that consisted of collecting any contaminants, transferring them into a Petri dish and awaiting development thereof in order to perform the appropriate tests. 
         [0005]    Use of the aforementioned technique, developed by the present applicant, requires the transfer of the filtration membrane onto a support plate that generally comprises a cellulose element or pad impregnated with a solution for marking the viable microorganisms. When this membrane is placed on the support plate, the problem posed of the possible creation of an air bubble between the membrane and the cellulose pad, this air bubble forming a screen that opposes the correct and complete reaction between the marking product and the microorganisms. To solve this problem, the users are invited to place the membrane on the support plate not in a single action generally directed perpendicular with respect to the support plate, but in an action in two phases comprising firstly putting the periphery of the membrane in contact with the plate and then applying the rest of the membrane against this plate. This “duplicated” manipulation drives out the air present between the membrane and the support thereof. 
         [0006]    In practice, many users use this methodology. However, this requires that said operator does not forget to use it. If he forgets, the test performed cannot be accepted as valid since the marking material will not have completely fulfilled its function. 
         [0007]    The present invention therefore aims to solve this difficulty by proposing means that make it possible to position a membrane correctly in its support plate so as to prevent the creation of an air bubble between them. Thus a first subject matter of the invention consists of an assembly consisting of a flat rigid filtration membrane, and a generally flat plate, for receiving and supporting this membrane, in particular with a view to the activating and/or revealing of contaminants immobilised thereon, this support plate comprising holding and immobilisation means able to cooperate with the periphery of the membrane. According to the invention, said means comprise at least one non-deformable member that projects above the overall plane of said plate and comprises at least one tab forming a stop, roughly perpendicular to said plane, which is extended by an retaining appendage roughly parallel to said plane, so that said membrane can be engaged with this member only in a first movement of the membrane substantially parallel to the plane of the plate, followed by a second movement substantially perpendicular to said plane. 
         [0008]    The presence of at least one non-deformable member constitutes an obstacle that opposes the direct engagement of the membrane on the plate in a movement with a direction roughly perpendicular to the plane thereof. By virtue of the features of the invention, it is therefore only possible to place the membrane on the plate in the aforementioned two movements, so that the operator does not need to be concerned about or remember the operations to be used since the objects that he is manipulating include means that will guide him in performing his manipulations. 
         [0009]    The term “membrane” means both a self-supporting membrane and a flexible filtration structure fixed to a rigid frame. The expression “first movement of the membrane substantially parallel to the plane of the plate” means that, when this operation is performed, the membrane occupies a position very close to the plate, parallel thereto or, at the very least, forming with it an acute angle of no more than a few degrees (10° to 15° maximum). 
         [0010]    According to other advantageous features of this assembly: 
         [0011]    it comprises at least one second member forming a locking member, which also projects above the overall plane of said plate, this member being elastically deformable so that, during said second movement, it retracts and then resumes it initial position, thus locking the membrane; 
         [0012]    said non-deformable member is situated opposite to and facing said second member; 
         [0013]    said membrane is provided with a lug able to cooperate with said non-deformable member; 
         [0014]    said lug is, see from above, in the general shape of a “T”; 
         [0015]    said membrane is provided with a lug able to cooperate with said second member; 
         [0016]    said lug is, as seen from above, in the overall shape of a Latin or Greek cross; 
         [0017]    said membrane fits in a circle, said lug extending radially, at the periphery of this circle; 
         [0018]    said plate comprises a region that supports said second member and is separated from the rest of the plate by a mechanical weakening zone, so that, following a mechanical force exerted on this region, it is given a particular orientation with respect to the rest of the plate, which makes it possible to release the membrane from said second member; 
         [0019]    said region forms an appendage with respect to the rest of the plate, said weakening zone being situated at the boundary thereof; 
         [0020]    said plate has, in the central part thereof, a recess able to accept material suitable for interacting with said membrane. 
         [0000]    Other features and advantages of the present invention will emerge from a reading of the following detailed description of a preferential embodiment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    This description will be given with reference to the accompanying drawings, in which: 
           [0022]      FIGS. 1 and 2  are views in perspective of a receptacle and a base forming a pedestal for this receptacle, these two elements constituting a test device; 
           [0023]      FIG. 3  is a view in perspective of the receptacle that appears in  FIGS. 1 and 2 ; 
           [0024]      FIG. 4  is a plan view of a membrane constituting the assembly and the device according to the invention; 
           [0025]      FIG. 5  is a perspective view of the base able to cooperate with the receptacle in  FIG. 3 , this base being here provided with a membrane and a sampling cap for the latter; 
           [0026]      FIG. 6  is a side view of the cap appearing in  FIG. 5 ; 
           [0027]      FIG. 7  is a plan view of the plate of the support constituting the assembly according to the present invention; 
           [0028]      FIG. 8  is a perspective view of the plate of  FIG. 7 ; 
           [0029]      FIG. 9  is a view in section along the plane IX-IX in  FIG. 7  of the support plate, this view being particularly intended to explain the way in which a membrane is placed on this plate; and 
           [0030]      FIG. 10  is a plan view similar to  FIG. 7 , in which the silhouette of the membrane is marked in broken lines. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    The receptacle  1  and the base  2  shown in the appended  FIGS. 1 and 2  form part of a microbiological test device. The receptacle  1  is intended to receive the liquid product that it is proposed to test. It has in some way a dual function of container and funnel. 
         [0032]    It comprises a flask  10  made from plastics material, closed by a removable cap  11 , which is provided with openings for connection thereof to a pump for example. This container is preferable transparent so that the operator can view the level of liquid that it contains. Its bottom part is referenced  12 , in one piece with the flask, and is in the general form of a cylindrical peripheral skirt. 
         [0033]    As shown more particularly in  FIG. 3 , this bottom part is provided with two scallops  120  disposed one facing the other, the function of which will be explained below. It also comprises two openings  121 , square in shape, that also face each other. Here also, the function of these openings will be explained below. 
         [0034]    As also shown in this  FIG. 3 , the bottom of the container  10 , which connects it with the bottom part  12 , is open at its centre in order to form a circular passage  13  the bottom side of which is fitted with a gasket  130 . This receptacle  1  is intended to engage with a base  2  forming a pedestal. This base  2  is in the general form of a cylinder and its peripheral external wall is, as shown in  FIG. 5 , provided with two protrusions  23  intended to engage with the complementary scallops  120  in the bottom part  12  of the receptacle  1 . 
         [0035]    This pedestal also comprises two tabs  21 , elastically deformable, which each carry a finger  210  intended to engage in the openings  121  in the bottom part  12  of the receptacle. These lugs  21  are made in one piece with the pedestal  2 . They are directed parallel to the longitudinal axis thereof and are separate from the rest of the pedestal. 
         [0036]    Under these conditions, it will be understood that the movement of engagement of the receptacle  1  on the base  2  is guided by the protrusions  23  and scallops  120 , while the locking of the receptacle on the base takes place automatically, by ramp effect, via the elastically deformable tabs  21 . These two elements are separated by exerting a pressure on the tabs  21  so as to cause them to retract slightly towards the centre and thus release the fingers  210 . Although this is not clearly visible in the figures, the pedestal  2  has, parallel to and above a bottom wall  22  provided with a discharge orifice  23 , a perforated surface, formed by a network of concentric flutes, which constitute a filtration surface. Such a structure advantageously replaces a sintered glass surface which, up until then, required to be supplemented by the use of a cellulose filter support. 
         [0037]    This filtration surface is intended to receive a rigid filtration membrane as shown in  FIG. 4 . This filtration membrane consists of a filtration structure  31  disposed on a circular-shaped rigid peripheral frame  30 . This frame  30  consists for example of a moulded plastics material, while the structure  31  of the membrane is for example based on polyethylene terephthalate with a usual thickness of around 23 micrometres and a porosity variable from 0.1 to a few micrometres. 
         [0038]    As shown in this figure, the membrane is provided with two diametrically opposed lugs. They form an integral part of the frame  30  and are made in one piece therewith. They extend in the same plane as the frame  30 . 
         [0039]    The lug  32  is in the general shape of a “T” with a base  320  that extends in the radial direction, and a slightly curved transverse bar  321 , which extends perpendicular to this base. The second lug is in the form of a Latin or Greek cross, with a radial base  330  and a transverse branch  331 . The advantage and function of these shapes will be explained below. 
         [0040]    This membrane is intended to come to be positioned on the filtration surface of the base  2  described above so that the structure  31  is superimposed on the aforementioned network of concentric flutes. To do this and as shown in  FIG. 5 , the base  2  comprises a cutout  24  for engaging the lugs  32  and  33  respectively. This cutout forms both an immobilisation means and positive location means. 
         [0041]    When the liquid to be tested has been filtered, any contaminants that it contains are retained in the structure  31  of the membrane  3 . The test operation next consists of marking and/or revealing these contaminants so as to be able to view them or even count them. To do this, it is necessary to take off the membrane in place on the base  2  in a sterile manner. This is because, in the contrary case, manipulation of the membrane by the operator would bring other types of contaminant. 
         [0042]    For this purpose, use is made of a takeoff cap  4  that appears in  FIGS. 5 and 6 . This cap comprises essentially a peripheral cylindrical skirt  4  the outside diameter of which corresponds, to within any clearance, to the outside diameter of the frame  30  of the membrane  3 . This peripheral skirt comprises two scallops  41  diametrically opposed to each other, directed parallel to the generatrices of the cylinder constituting the skirt. 
         [0043]    Each scallop  41  has a broadened lower part  420  with convergent edges  420 . In the state shown in  FIG. 6 , the separation between the edges  420  is less than the width of the bases  320  and  330  of the lugs  32  and  33  of the membrane. The cap  4  is moreover provided with two diametrically opposed brackets  44  that project upwards, above the skirt  40 . They are distant angularly from the scallops  41  by 90°. Moreover, a gripping handle  43  extends perpendicular to the brackets  44 . 
         [0044]    This cap  4  is intended to engage on the membrane  3  when it is positioned on the pedestal  2 . This movement takes place downwards in the direction of the arrow f in  FIG. 6  while the scallops  42  are positioned vertically in line with the lugs  32  and  33  facing the bases  320  and  330  thereof. 
         [0045]    By pressing on these brackets, the convergent edges  420  separate by elastic deformation and snap elastically onto these lugs so as to be fixed thereto. This separation movement is represented by the arrows g in  FIG. 6 . To proceed with the reverse manoeuvre, that is to say detaching the membrane  3  from the cap  4 , it suffices to exert a pressure on the brackets  44  in the direction of the arrow h, which separates the two opposite parts of the skirt  40  in the direction of the arrow j, and then releases the lugs of the membrane. 
         [0046]    This operation of “releasing” a membrane is performed so as to effect its transfer onto a reception and support plate that appears in particular in  FIGS. 7 and 8 . This plate is intended to permit the marking and/or revealing of the contaminants carried by the membrane  3 . 
         [0047]    This solid, that is to say non-perforated, support plate  5  is a plate made from moulded plastics material, generally flat, with a mid-plane referenced P in  FIG. 9 . This plate is provided with an appendage  53  that is situated in the&#39; aforementioned plane P and is in one piece with the rest of the plate. This appendage  53  comprise, in its area of attachment to the rest of the plate, a mechanical weakening line  530 , represented by a groove the function of which will be explained below. The plate has, on its top face, moulded in one piece, a centred circular wall  50  the diameter of which is equal to the inside diameter of the frame  30  of the membrane  3 . 
         [0048]    Inside the recess R delimited by this wall, elongate-shaped studs  500  are arranged. This recess R is intended to accept a material such as a cellulose pad soaked in a material able to mark or reveal the contaminants carried by the membrane. 
         [0049]    The plate  5  also comprises other walls  51 , which for their part are formed in portions, which represent the rim of the plate. These walls fit in a circle the diameter of which is slightly greater than the outside diameter of the membrane  3 . 
         [0050]    The plate  5  comprises means of holding and immobilising the membrane  3 . These means comprise a non-deformable member  6 , which is positioned opposite and facing the appendage  53 . This member  6  consists of a tab  60  forming a stop, which extends from the plate  5  vertically upwards, in a direction roughly perpendicular to the plane P. This lug is extended, parallel to the plane P, by three horizontal appendages  61 . 
         [0051]    In addition, the aforementioned appendage  53  comprises a second member  7  forming a locking member, which also projects above the overall plane and the plate, this member  7  being elastically deformable. As shown more particularly by  FIGS. 8 and 9 , this member  7  is in the form of a hook, with a foot  70  perpendicular to said plane P, and a locking finger  71 , roughly parallel to this plane P. 
         [0052]    The membrane is placed on the support in the following manner. Using the aforementioned cap  4 , the lug  32  of the membrane  3  is positioned in a movement substantially parallel to the plane of the plate  5  and represented by the arrow k in  FIG. 9 . In any event and failing a strictly parallel movement, the axis formed by the membrane  3  and the plan P is an acute angle a, of a few degrees. In doing this, the transverse bar  321  of the lug  32  is engaged inside the non-deformable member  6 . 
         [0053]    Next, by a movement represented by the arrow  1  and directed substantially perpendicular to the plane P, the rest of the membrane is then engaged so that the second lug  32  elastically deforms the member  7  in the direction of the double arrow m, the finger  71  then coming to be locked on the lug  33 . It is clear that, by reason of the non-deformable character of the member  6 , any other method of engaging the membrane on the plate is not possible, in particular in a movement perpendicular to the plate. The movement described here makes it possible to drive out the air and thus prevent the formation of a bubble between the membrane and the cellulose pad placed on the plate, which ensures for the operator a good marking or revealing of the membrane by the material soaking the cellulose. 
         [0054]    In any event, the operator does not need to ask the question as to whether or not he has performed the correct action, since the means that equip the plate guide him and enable him to perform only the required action. When the operation has been performed, the membrane  3  occupies the position shown in broken lines in  FIG. 10 . Once this operation has been performed, it then suffices to leave the membrane  3  to incubate on its support plate  5  within an enclosure provided for this purpose, for a time and temperature specific to the protocol to be implemented. 
         [0055]    To separate the membrane  3  from the plate  5 , a downwardly directed force (in the direction of the arrow q in  FIG. 9 ) is exerted on the appendage  53 . This causes breakage thereof at the weakening zone  530 , or at the very least tilting thereof, in the direction of the arrow r, with respect to the plate  5 . By virtue of this movement, the lug  7  disengages from the membrane  3 , so that it is possible to proceed with the removal of the latter. Naturally, if the membrane is to be the subject of other test operations, it will be removed with the cap  4  described above.