DE102010006473B4 - Microbiological culture plate with integrated smear system - Google Patents

Abstract

The invention relates to a microbiological culture plate with an integrated smear system for the emersed cultivation of microorganism cultures, which enables aseptic work outside of sterile laboratory conditions and liquid samples to be tested - without having to open the culture plate - are applied decentrally to a culture medium and evenly spread there . It is characterized in that the cover (2), which extends over the lower part (1) and is elastically flexible on its side edges, on the inside of which is a firmly attached smear system with a lip (8) - consisting of an elastomeric plastic - is located on its lower side Edge inwardly directed guide pins (6) / guide webs (12) which are guided in a guide groove (5) so that a defined set distance (H) between the inside of the lid and the upper edge of the lower part (1) can be reversibly overcome and the lip (8) of the smear system comes into effective contact with a liquid sample and the solid nutrient medium (3) when the lid (2) is rotated relative to the lower part (1).

Description

The invention relates to a microbiological culture plate with an integrated smear system for emersive cultivation of microorganism cultures, with it aseptic working outside sterile laboratory conditions is possible and to be tested liquid samples - without having to open the culture plate - applied decentralized on a nutrient medium and evenly spread there ,

In microbiological laboratories, the use of sterile Petri dishes made of glass or plastic for the emersive cultivation of microorganism cultures on solidified nutrient media is customary and widely used. A large field of application is the determination of living germ counts as CFU (Colony Forming Units), for. B. to examine the bacterial load in wastewater and drinking water, food or in medical diagnostics. Using specific selective nutrient media, individual strains (eg pathogenic bacteria) or groups of microorganisms (eg molds) are also determined explicitly. Such a method is relatively simple. For germ count determination, a liquid sample aliquot (usually 100 μl) is applied to a sterile, solidified culture medium in a Petri dish and distributed evenly and completely on the surface by means of a sterile tool. The sample fluid is absorbed by the nutrient medium and proliferating germs begin to grow on the surface to form a visible colony. These can be counted after a corresponding incubation period.

One problem, however, is that compulsory aseptic conditions must be present for a sample smear, but this is not the case with a known two-part openable petri dish, due to concomitant contamination by surrounding germs, outside of sterile laboratory conditions. Thus, a germ-free operation can only be performed in the sterile area of microbiological laboratories. To perform the procedure under field conditions, e.g. B. in the sterile environment of a burner flame, compromises and the quality-compliant design is not guaranteed.

A large field of application for microbial determinations outside of laboratories can be seen in the assessment of environmental samples (eg samples of water), drinking and industrial water samples in the private sector as well as commercial samples (eg samples of composting or waste processing).

Inquiries from the population show that there is an increasing interest in self-monitoring regarding the hygienic safety of drinking and industrial water. First of all, service water, rainwater and well water are in the focus of interest, as these sources are often used in rural areas for water / wastewater and therefore cost savings.

According to the current state of the art, the liquid samples after sampling always have to be sent to commercial laboratories to be tested there. This is expensive, time consuming and involves the risk of changing the sample during transport times.

Another problem is the control of microbiological indoor air pollution, z. B. by airborne mold spores. There are various sampling devices for the separation of these germs. A distinction is made between indirect and direct filtration methods as well as impactor methods and impinger methods. They allow a renovation-accompanying assessment of mold-contaminated buildings. The clear microbiological assessment of the contamination status is not only the prerequisite for the selection of suitable remediation methods, but it is also the criterion for documenting the rehabilitation success after the measure.

If the germs are deposited directly on agar plates (impactor method), then an immediate incubation can take place. However, if the germs are first deposited into a collecting liquid after the impinger process, which is particularly appropriate at very high concentrations, this sample must then be spread on culture plates in a timely and defined manner.

An essential facilitation and process improvement is when on-site sample further processing, d. H. a smear of liquid sample materials on culture plates would be possible.

This requires a closed, sterile disposable cultivation system with appropriate nutrient medium, in which the sample application and distribution can be carried out with the simplest of hands by the layman, without causing foreign contamination. The incubation of the self-inoculated plates can then be carried out by the user, usually even at room temperature, and count out the forming colonies.

With such a self-contained Petri dish system, which can also be offered inexpensively as a mass-produced, private users could be addressed at the same time, a self-control of aqueous samples in the household (drinking water, process water, well water, gray water, rainwater, aquariums, Ponds, etc.) with regard to the germ load.

To explain the previously known prior art will be further elaborated.

Direct cultivations on solidified nutrient media are customary for a meaningful determination of germ count in aqueous samples. Among the cultivation conditions optimal for the respective species or groups of microorganisms sought, there is the proliferation of living germs and the expression of colonies which are visible on the medium and can be counted. This ensures that only reproducible germs are recorded, which is why the result is given as "colony forming units (CFU / ml)". This result form is relevant for most applications in the field of hygiene, medicine and biology.

By choosing the nutrient medium and the incubation conditions, it is possible to select which germs develop. Therefore, it is possible to single strains or groups of microorganisms such. B. selectively detect molds.

In a known manner, the plating of the sample on the surface of a nutrient medium (surface spatula method) is carried out for the determination of aerobic bacteria. For this Petri dishes are used, consisting of shell bottom and overlapping lid. For the smear is in the sterile area, z. B. under a laminar flow box, with sterile instruments, a sample amount manually and distributed as spatula (Drigalskispatel) as evenly as possible. This can not be carried out in a quality-appropriate manner outside of a sterile area, since the plates must be opened for sample application and sample smearing and as a result the nutrient medium is contaminated by germs from the environment.

There are now various devices and methods for different modifications and special applications described, where it is possible to multiply germs with different oxygen compatibility (anaerobic, microaerophilic) by overlaying with liquid culture medium or mixing the sample in initially liquid medium is carried out ( pour plate method). Likewise, various metabolic activities can be visualized via indicators in the nutrient medium.

Specific examples of the prior art will be discussed in more detail below.

So is after DE 37 05 229 C2 a method for the determination of microbial contents by a plate casting process and thereby called shells called. Here, the culture medium and sample are homogeneously mixed with each other, whereby the layer thickness is varied by the geometry and size of the shell / -n and by the introduced volume. The shells have a round or rectangular shape with bottoms that differ from each other z. B. concave, convex, linear rising, are designed. This should be evaluable different concentration ranges. A uniform smear of a sample under field conditions to obtain an emersed microorganism growth is not possible thereby.

To US 4,358,539 A describes a disposable culture system, aseptically in a simple manner, a transfer of a liquid sample, for. B. from liquid cultures, is performed on a nutrient medium by the sample is transferred via an internal cannula on an absorbent fiber tissue disc, which rests centrally on the solid medium. From this central pad, the culture grows radially onto the nutrient medium. Although microbial transmissions for simple control tasks are possible with this system, eg. B. for purity control of a culture, but no quantitative germ count. An active and even distribution of the sample on the culture medium surface does not occur. The amount of liquid transferred is not checked.

With US 5,830,746 A describes an apparatus and a method for growing anaerobic microorganisms. It is formed here by an annular sealing surface in the lid a closed gas space in the cultivation room when the plate is stored upside down. Devices for sample application and distribution are not provided. Therefore, the system must be opened for inoculation, as in conventional petri dishes, whereby an application in contrast to the present invention is possible only under aseptic conditions.

In EP 1 528 100 B1 a lockable contact plate is shown. There is a plate with a bottom plate and a lid via a locking mechanism in operative connection. The elements must be opened when sampling, so that aseptic working under field conditions is not given. Distribution elements are not available.

Finally, be on DE 690 108 56 T2 which mentions a disposable culture dish with reinforcing ribs. Here, the Petri dish has inside upstanding ribs on the ground, which serve only to reinforce the thin glass material. These hinder a uniform spreading of a sample, this culture dish must also be opened and thus no safe germ count reading allows.

For germ count also so-called "dip-slides" are used. This is a culture method for (semi-) quantitative determination of bacterial count from aqueous media. The dip-slides can also be used to determine the surface bacteria count.

The "Dip-Slides" are commercially produced, double-layered, flexible plastic carriers that were originally developed for urine diagnostics. Meanwhile, they are also widely used in technical fields.

The support plate of the immersion slide is usually loaded on the top and bottom with two different culture media for total bacterial count of bacteria and yeasts / molds. In addition, there are still systems with three-sided carrier plates.

Various companies have developed dip-slides for hygiene checks. The manufacturers offer dip-slides with different nutrient media. There are accordingly agar for total bacterial count or Selektivnährmedien for the detection of z. Enterobacteria or for the detection of yeasts and fungi.

In contrast to the proposed invention, in the case of dip-slides, a non-sterile sampling and an undefined sample quantity and distribution are deliberately accepted, which is absorbed on the nutrient medium surface by the immersion. Although "dip-slides" are kept in a sterile tube and shipped. For sampling, however, the culture medium must be removed for a short time and placed in an aseptic environment.

The proposed invention has the advantage over the "dip-slides" that a precisely defined amount of sample can be distributed completely and evenly on a defined culture medium surface. As a result, the determined colony numbers can be very accurately related to the sample volume. In addition, according to the invention, the culture medium for sample application is never exposed to an unsterile environment.

On the basis of the prior art discussed herein, it becomes clear that a solution must be sought which overcomes the disadvantages of the previously known.

It is therefore an object of the invention to develop a generic Petri dish as a microbiological culture plate with an integrated smear system such that an overlapping in a lower part lid in guides on the circumference of the lower part slidably encloses a preferably aseptic interior, which remains closed for sample application, in the lid on a nutrient medium and on a sterile applied externally applied sample lowerable and circular movable smear element is fixedly mounted, which can be raised after the smear by an opposite rotation between the lid and base back to its original position over the streaked uniformly on the culture medium sample. By means of a suitable septum in the lid, in particular off-center septum, a sample should be able to be sterilized on the nutrient medium by means of a suitable sample application system. The culture plate according to the invention should be simple and inexpensive to manufacture and uncomplicated to handle.

According to the invention, the object is achieved as follows, reference being made to the basic inventive idea on the features of claim 1. The further embodiment of the invention is specified in the claims 2 to 10.

The inventive solution requires further information.

The microbiological culture plate presents itself as a self-contained system for the cultivation of microorganisms. It consists of a cover overlapping a lower part - initially similar to a known Petri dish - but with a special edge formation on the lower edge of the lid and on the outer circumference of the lower part, the actual shell , are suitable to prevent accidental opening of this self-contained system. The lower part contains inside on its bottom already there firmly introduced nutrient medium with a defined volume, which is reached by the lowerable cover with its integrated smear system so by guiding pins or guide bars attached to the end of the lower part encompassing the lid edge, in a guide groove on the outer circumference of the lower part engage and during lowering and twisting of the lid relative to the lower part in a clockwise direction on a thread-like slope of an inclined plane in an annular peripheral region of the guide groove in the lower part are feasible, so that there twisting of the lid relative to the lower part can be done by at least 360 °. It reaches the particular made of elastic and transparent material existing lid, which develops internal mechanical stress during its lowering and turning, again its initial position, if it counterclockwise, the thread-like pitch in the opposite case overcomes and on the initial position locking locking elements is performed.

In the initial position of the lid relative to the upper edge of the lower part, such a distance corresponds to that which the fixedly attached to the inside of the lid smear system, consisting of at least one radially dimensioned web and an elastic lip pointing down there, overcomes in order to reach at the nutrient medium the sample introduced by at least one septum and to distribute it evenly in a circular manner. The septum is located in the cover in the outer center position, wherein it should generally be noted that the lid and the lower part are designed to secure the function of the invention as rotationally symmetrical elements. The lower part is to be advantageously heat-resistant, transparent glass or plastic, so that at least temperatures of 90 ° C can be realized, which is necessary for the production in order to fill the initially hot, liquid medium.

Finally, it is provided that all elements of the microbiological culture plate consist of sterilizable, preferably radiation sterilizable materials.

For aerobic microorganism cultivation lid and base are unweighted against each other, so that over the slightest material tolerances a gas exchange with the environment is given, without it can lead to foreign infections.

It is conceivable that the lowering of the lid is also possible by means of another geometric shape of a portion on the outer periphery of the lower part and holding elements of the lower lid edge in this sub-region in the rear handle with a guide element, from which they can be released again to the back as in the aforementioned spacing to get between the lid and lower part.

It should be made to below mentioned advantageous embodiments.

Thus show:

1 FIG. 2: sectional view of the microbiological culture plate with a guide groove in the lower part, which has a thread-like gradient,

2 : Top view of the microbiological culture plate from above gem. 1 .

3 : Side view acc. of the 1 and 2 of lid and base,

4 FIG. 2: a sectional view of the microbiological culture plate with a conical region and a guide web in a partial region of the outer circumference of the lower part,

5 : Top view of the microbiological culture plate from above according to 4 .

6 : Side view of the microbiological culture plate according to the 4 and 5 of lid and base.

The reference numbers used in the figures are listed in a separate list of reference numerals:
To 1 there is a lid 2 and a lower part 1 a microbiological culture plate via a guide groove 5 , introduced approximately in the middle of the outer circumference at the lower part 1 , and guide pins 6 in positive connection, causing an unwanted lifting of the lid 2 is prevented. In the initial position is the lid 2 with a defined distance H + x with its inner side cover spaced from the upper edge of the lower part 1 , which also corresponds to the height that is sufficient to the lid 2 internally attached smear system, consisting of a bridge 7 and a lip 8th , on the surface of a solid nutrient medium 3 lower.

About an off-center in the lid 2 existing septum 4 In this case, a sample liquid in a defined amount in the self-contained culture system can be introduced.

The lowering becomes possible by turning the lid 2 clockwise against the lower part 1 the lid made of flexible and transparent material 2 , over an upper and inclined section 10 . 11 the guide groove 5 its starting position, when overcoming the resistance, the locking points 9 exercise, leaving, eventually reaching the lowest and circumferential area of the guide groove 5 a barrier-free turning of the lid 2 and thus allow the spread of the sample.

In a similar form, the structure of microbiological culture plate according to 4 In contrast to the first embodiment, the lower part has 1 outside, as seen from its center and towards the bottom, a conical recess 14 with a horizontally and in this area centrally arranged leading edge 13 caused by several interruptions 15 Having openings through which guide webs 12 of the lid 2 , by pressing on the lid 2 , so they pass into a rearward grip to a horizontal leading edge 13 in the lower part of the conical recess 14 to be brought. In this phase of lowering by the distance H also has the lid here 2 an internal tension of material that overlaps him with overlaps 15 to return to his starting position. Below the leading edge 13 results in the circumferential, by cover rotation, usable guide 5 ,

• – Durchführung von Arbeiten zur emersen Kultivierung von Mikroorganismenkulturen, auch im Feldversuch, aseptisch möglich,
• – hohe Sicherheit bei der Keimzahlbestimmung,
• – Handhabung auch von Nichtfachleuten gegeben,
• – einfach und kostengünstig herstellbar.

The advantages of the invention can be summarized as follows:

• - carrying out work for the emersive cultivation of microorganism cultures, also in field trials, aseptically possible,
• - high safety in germ count determination,
• - Handling also by non-experts,
• - easy and inexpensive to produce.

LIST OF REFERENCE NUMBERS

1

lower part

2

cover

3

fertile soil

4

septum

5

guide

6

guide pin

7

web

8th

lip

9

Arretierungspunkt

10

upper section

11

inclined section

12

guide web

13

leading edge

14

conical recess

15

interruption

H + x

Distance + manufacturing tolerance

H

distance

Claims (10)

Microbiological culture plate with integrated smear system, wherein the culture plate consists of a lower part ( 1 ) with a solid nutrient medium ( 3 ) and from one of the lower part ( 1 ) overlapping lid ( 2 ), which is a septum ( 4 ), which are both rotatable against one another but can not be opened, so that they form a closed environment with respect to the environment, characterized in that the microbiological culture plate a) has the lower part ( 1 ) overlapping and elastically yielding at its side edges ( 2 ), b) on the inside of the lid ( 2 ) a firmly attached smear system with a lip ( 8th ) made of an elastomeric plastic, c) at the lower edge of the lid ( 2 ) with inwardly directed guide pins ( 6 ) and / or guide webs ( 12 ), which are in a guide groove ( 5 ), is equipped, d) in its initial state between the inside of the cover and the upper edge of the lower part ( 1 ) shows a defined set distance (H), which by means of mutual rotation between the lid ( 2 ) and lower part ( 1 ) is reversible and e) on the reversible adjustment between the lid ( 2 ) and the lower part ( 1 ), within the distance (H), an effective contact between the lip ( 8th ) of the smear system, a liquid sample and the nutrient medium ( 3 ). Microbiological culture plate according to claim 1, characterized in that the guide pins ( 6 ) after overcoming locking points ( 9 ) from an upper section ( 10 ) of the guide groove ( 5 ) via a short thread-like slope of a sloping section ( 11 ) in the guide groove ( 5 ), which circumferentially on the outer periphery of the lower part ( 1 ) is formed, upon rotation of the lid ( 2 ) are clockwise feasible. Microbiological culture plate according to claims 1 and 2, characterized in that, when turned counterclockwise, the lid ( 2 ) is traceable to its initial position. Microbiological culture plate according to claim 1, characterized in that the smear system consists of at least one radially arranged web ( 7 ) and a lip attached thereto ( 8th ) consists. Microbiological culture plate according to claim 1, characterized in that at least one septum ( 4 ) in the lid ( 2 ) is mounted off-center. Microbiological culture plate according to claim 1, characterized in that the lower part ( 1 ) on the outer circumference of a circumferentially widening in the direction of the bottom conical recess ( 14 ), wherein in the middle of a horizontal leading edge ( 13 ) with one or more interruptions ( 15 ) defined width, wherein below the leading edge ( 13 ) the circumferential guide groove ( 5 ) is located. Microbiological culture plate according to claim 1 and 6, characterized in that the guide webs ( 12 ) of the lid ( 2 ) through the interruptions ( 15 ) in the leading edge ( 13 ) are guided through and a rotation of the lid ( 2 ) in the lower region of the conical recess ( 14 ) is given by 360 °. Microbiological culture plate according to claims 1 to 7, characterized in that the lid ( 2 ) made of flexible plastic material, which like the material of the lower part ( 1 ) is transparent. Microbiological culture plate according to claim 1, characterized in that the lower part ( 1 ) made of heat-resistant material for temperatures up to 90 ° C. Microbiological culture plate according to one of the preceding claims, characterized in that all elements of the culture plate consist of sterilizable, preferably radiation sterilizable, materials.

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