Device and method for microbiological analysis of biological samples

The device for microbiological analyzes on samples of body fluids comprising: an incubation area for containers containing said samples; an analyzer for analyzing the inner atmosphere of said containers; a sorting system to sort the containers according to the carbon dioxide content detected by said analyzer.

TECHNICAL FIELD

The present invention relates to methods and devices to perform analyses of biological samples, and more in particular microbiological analyses aimed at verifying the presence of bacteriologically significant concentrations of microorganisms inside biological samples, such as in particular, although not exclusively, samples of body fluids, such as urine and blood.

STATE OF THE ART

The performance of microbiological analyses on biological samples, in particular body fluids, is well known, in order to verify the presence of pathogenic agents, generally microorganisms that can have a harmful effect on the health of humans or animals. This type of analyses is usually carried out on urine, blood, feces and buffers. In general, verifying the presence of pathogenic agents inside the sample is not sufficient, and it is also necessary to classify them, i.e. to verify what type of microorganism is involved, in order to check its harmfulness to the health and to prescribe the necessary treatments.

The traditional methods for microbiological analysis of urine samples are based upon the so called seeding, which provides for the distribution of the sample to be analyzed on a growth medium, leaving it there for a high number of hours (typically 12 hours or more), in order to verify whether microorganism colonies grow on the medium or not. If so, these microorganisms are examined in order to check the nature thereof.

When more samples must be analyzed, the seeding process is extremely long lasting, and requires some preparation by the operator who performs it. Handling a high number of samples entails biological risks, as well as risks linked to the possibility of confusing the samples with each other, thus wrongly attributing the analysis results to the patients.

In F. Gardini et al. “A head space gas chromatographic approach for the monitoring of the microbial cell activity and the cell viability evaluation” Journal of Microbiological Methods, 29 (1997) 103-114, an approach is described based upon the gas chromatography to detect the microbial activity inside the samples to be analyzed. The gas chromatography aims at identifying the carbon dioxide (CO2) concentration present in the atmosphere in which the sample is, and whose presence is due to the metabolism of the microorganisms present in the sample. This approach requires complex and expensive equipment, as well as long analysis times.

U.S. Pat. No. 4,971,900 describes a method and a device for the detection of biologically active agents in samples of various nature, for example also urine. The method is based upon the analysis of the carbon dioxide content in the atmosphere above the sample, which is positioned on the growth medium. The analysis lasts many hours, and aims at identifying any pathogenic agent by means of the trend of carbon dioxide development over time. This analysis method requires extremely long times and is not particularly reliable as the detection of the microorganism depends upon the correct tracing of the time curve of the carbon dioxide development. In particular, problems may arise when pathogenic agents of different type are present inside the sample, which develop according to times different from each other.

U.S. Pat. No. 6,709,857 describes a system for optically detecting the gas concentration in a vial containing a sample to be analyzed. The gas concentration is detected by means of photothermal spectroscopy.

U.S. Pat. No. 5,155,019 describes a method for detecting the presence of biological activity in a sample utilizing an infrared analysis of the sample sealed in a container, in order to identify the presence and the concentration of carbon dioxide in the atmosphere above the sample cultured inside the container. In this case again, particularly long times are required for the analysis, as well as a complex equipment.

U.S. Pat. No. 5,217,876 describes a method for detecting the presence of microorganisms in a sample inside a container. The method is based upon the idea of optically detecting a change in the color of an indicator medium in the container in which the sample is cultured, change that is due to the development of carbon dioxide because of the presence of a microbiological activity inside the sample. In this case again, long times are required for the analysis and, as in the previously mentioned case, the identification of the pathogenic agent present in the sample is not particularly reliable, as it is based upon the trend of the carbon dioxide development over time.

A similar method is described in U.S. Pat. No. 5,094,955.

U.S. Pat. No. 5,482,842 describes a further method for detecting microorganisms within body fluids, in particular a blood sample. The analysis is carried out through an infrared light source and an infrared detector. In this case again, the presence of carbon dioxide is detected, which develops due to the presence of pathogenic microorganisms. Carbon dioxide has an infrared radiation absorption coefficient different from that of the atmosphere normally present (in the absence of pathogenic agents) above the level of the sample inside the vial.

U.S. Pat. No. 5,856,175 describes a device for the detection of pathogenic agents in samples of body fluids, which is similar to the device described in U.S. Pat. No. 5,094,955 and in U.S. Pat. No. 5,217,876.

U.S. Pat. No. 5,814,474 describes a device for the direct detection of microorganisms in culture bottles. The described device is used for the analysis of samples of urine, saliva or blood. Substantially, the method described herein is based upon the analysis of the atmosphere contained in the vial inside which the cultured sample is inserted. The gas inside the vial is made pass through gas sensors in order to detect the composition thereof and then to identify, based upon the result of the gas analysis, the microorganisms present in the sample. This analysis method is particularly complex, requires very expensive sensors and long analysis times.

SUMMARY OF THE INVENTION

According to one aspect, the present invention provides for a method that simplifies and accelerates the operations for the analysis of body fluids, in particular but not exclusively urine. According to some embodiments, the method according to the present invention allows to distinguish, in a plurality of samples, the surely positive samples from the surely negative ones, i.e. to distinguish the samples inside which at least one pathogenic agent is present, which must be identified in a second more accurate analysis phase, from the sample surely devoid of pathogenic agents, for which it is therefore useless to perform further analyses.

In this way, during the subsequent phase of analysis of the samples, which can be carried out through a seeding process or other known process, only some of the originally considered samples are treated, whilst the surely negative samples do not require further processing.

According to one embodiment, the method according to the present invention comprises the following steps:a) introducing a biological sample to be analyzed in a test tube containing a growth medium;b) incubating the test tube for a first time interval;c) analyzing, following the first time interval, the atmosphere in said test tube;d) determining, based upon the carbon dioxide quantity detected in the atmosphere, whether the biological sample contains a pathologically relevant bacterial load or not.

The present invention is substantially based upon the idea of using the carbon dioxide quantity detected in the atmosphere inside a sample not for identifying the type of pathogenic agent, which may be present in the sample, as in the traditional methods, but as a parameter to distinguish surely negative samples from the surely positive ones. The identification of the type of pathogenic agent present in the positive samples will be carried out in a subsequent more accurate analysis phase, e.g. a seeding process, or other known systems, for example described in the patent documents mentioned in the introductory part of the present description. However, the only methods that currently allow to identify in a reliable manner the type of microorganisms present in the samples are those based upon the seeding, characterized by the drawbacks described above.

In one embodiment of the present invention, it is possible to provide for two threshold values, with which the carbon dioxide content that develops after a given time inside each single container of cultured sample is compared. In some embodiments it is possible to provide for the samples, whose carbon dioxide content after the preset incubation time interval is greater than a first limit value, to be classified as surely positive, and vice versa for the samples that after the same incubation period present a carbon dioxide content lesser than a second lower limit value, to be classified as surely negative. The intermediate samples can be considered uncertain and, for greater reliability of the analysis, they can be subjected to a detailed analysis in order to verify the presence and the type of microorganisms.

Vice versa, according to a modified embodiment of the present invention, the uncertain samples, instead of being subjected to a detailed analysis, for example to a seeding process, can be subjected to a second incubation interval, renewing the atmosphere present in the single containers of the samples, if necessary. This renewal of the atmosphere allows to eliminate the carbon dioxide presence and to add oxygen in order to develop the metabolism of the microorganisms present in the sample, if any. After a second incubation time interval, the uncertain samples are subjected again to a verification of the carbon dioxide content in the atmosphere of the container. This content is then compared with a threshold value, which distinguishes between surely positive samples (for which the carbon dioxide content is greater than the threshold value) and surely negative samples, for which the carbon dioxide content is lesser than the threshold value.

Through this second operating method it is possible further to reduce the samples that must be subjected to the subsequent seeding process, as the samples, which have been determined as uncertain through the first analysis phase, are further subdivided into surely positive samples and surely negative samples. These latter are not subjected to seeding or other analysis process in order to determine the type of pathogenic agents contained inside them.

Further advantageous embodiments and possible features of the method according to the present invention are indicated in the appended claims and will be described in greater detail hereunder with reference to one embodiment.

According to a different aspect, the present invention relates to a device for microbiological analyses of samples of body fluids, such as urine or the like, comprising:

an incubation area for containers containing said samples;

an analyzer for analyzing the inner atmosphere of said containers;

a sorting system to sort the containers according to the carbon dioxide content detected by said analyzer.

Substantially, in some embodiments the device provides for an incubation area, where the samples contained inside the single containers are incubated for an adequate period of time, for example of around one hour. The samples are then analyzed through the analyzer, and sorted, i.e. subdivided into positive samples and negative samples. In an improved embodiment the sorting system subdivides the samples that have been subjected to this first incubation into surely positive samples, surely negative samples and uncertain samples. The device can present a second incubation area for the uncertain samples, where they stay for a second incubation time interval, if necessary following the renewal of the atmosphere inside their containers due to the above described reasons. It is also possible for the second incubation phase to be carried out in the incubation area, where the first incubation of the single samples occurs. The equipment will be adequately controlled by a microprocessor, so that it can store in a memory information relating to the position of the containers with the samples that are performing the first incubation phase and the samples that are performing the second incubation phase, so as to avoid errors in the execution of the first and of the second incubation phase of the various samples contained inside the analysis equipment or device.

Further advantageous features and embodiments of the device according to the present invention are indicated in the appended dependent claims and shall be described in greater detail with reference to a non-limiting embodiment of the invention.

According to a further aspect, a further object of the present invention is to provide a test tube for the analysis method and for use with the equipment according to the present invention. More in particular, according to one embodiment the test tube of the present invention is a vacuum test tube containing a growth medium suitable to the development of microorganisms that may be present in the specific biological sample to which the test tube is destined, as well as a magnetic agitating element located inside the test tube.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

With reference toFIGS. 1 to 3, a device according to the present invention, indicated as a whole with number1, comprises a loading area3for loading racks R of containers P, in which single racks of containers P containing the biological sample to be analyzed are inserted and handled according to the arrow f5by a first conveyor5.

In the illustrated embodiment the containers are vacuum test tubes, with a seal cap, but it should be understood that also containers of different type can be used, sealed in order to detect, if necessary, the accumulation of carbon dioxide inside them due to the metabolism of microorganisms, if any, which are contained in the sample and develop thanks to a growth medium contained inside the test tube where the sample is positioned.

Adjacent to the load area3, an incubation area7is provided, where a second conveyor9is arranged, which moves the racks R of test tubes P according to the arrow f9.

The number11generally indicates a rest area for test tubes P, preferably housed in a rack R, containing uncertain samples that must be subjected to a second incubation. Between the incubation area7and the rest area11an analyzer, indicated as a whole with the number13, and a sorter, indicated as a whole with the number15, are arranged. The analyzer performs in sequence on the single test tubes P of the racks R coming from the incubation area7the analysis of the atmosphere contained inside the test tubes. Based upon the result of the analysis performed by the analyzer13, the sorter15sorts the test tubes, subdividing them into test tubes containing positive samples, i.e. samples on which an analysis must be performed to identify the pathogenic microorganisms contained in the sample, and test tubes containing negative samples, i.e. on which a further analysis is not required, as they do not contain significant pathogenic agents, and lastly test tubes containing uncertain samples which are carried to the rest area11in order to be subjected to a second incubation phase.

With specific reference to the loading area3, single racks R, containing test tubes P in which samples to be analyzed are arranged, are inserted inside it through an aperture closed by a door17(FIG. 2). The conveyor5transfers in a stepped manner the single racks R from the position of insertion in the load area3towards a transferring unit21, which transfers the single racks R of test tubes P from the loading area3to the incubation area7. In some embodiments the transferring unit21comprises a continuous flexible member23driven around pulleys25,27, at least one of which is motorized. To the flexible member23one or more pushers29are fixed, which push the single racks R containing the test tubes P in order to handle them according to the arrow f21in a direction orthogonal with respect to the feed direction f5of the conveyor5. The transferring unit can also assume different configurations, for example it can comprise a threaded rod, to which a cursor with a pusher is engaged. The rotation of the rod in a direction and in the opposite direction causes the feed and the return of the cursor and the related pusher.

Whichever configuration has the transferring unit21, it provides to transfer the single racks R containing the test tubes P of samples to be analyzed from the loading area3, which can be maintained at a low temperature in order to inhibit or to slow down the metabolism of the microorganisms, if any, present in the samples, to the incubation area7, preferably maintained at a controlled temperature, for example around 37° C.

In the incubation area7the conveyor9moves in a stepped manner the single racks R with the test tubes P from the position, in which they are inserted from the transferring unit21to the incubation area7, towards an analyzing and sorting area, where the analyzer13and the sorter15are arranged.

In the analyzing and sorting area a second transferring unit31is provided, similar to the transferring unit21and comprising for example a flexible member33driven around pulleys35,37. To the flexible member33one or more pushers39are constrained, which push with a stepped controlled movement the single racks R towards a sorter. The transferring unit31is controlled by a programmable electronic control unit, not shown, in such a way as to feed each rack R in a stepped manner according to the arrow f31, taking it off from the conveyor9and passing individually the single test tubes P contained in the rack R through the analyzer13. In this way, each test tube can be analyzed by aspirating a sample of the atmosphere contained inside it and determining the carbon dioxide content which has developed in the test tube due to the effect of the metabolism of the pathogenic microorganisms, if any, which can be contained inside the sample cultured in the test tubes P during the incubation period in the incubation area7.

The incubation has a modest duration with respect to the incubation times used in the traditional analysis systems, and lasts for example about one hour, the convey9being programmed to move with such a speed that the incubation time is substantially equal to the time a single rack needs to pass from the position where the transferring unit21is located, to the position where the transferring unit31is located.

As shown in particular also inFIG. 4, in this embodiment the analyzer is double, and comprises a first sensor41A and a second sensor41B, realized to determine with a sufficient precision the carbon dioxide content inside the single test tubes P. With this double arrangement it is possible to double the speed of analysis of the device. Each sensor41A,41B can be made in NDIR technique, as described for example in U.S. Pat. No. 6,255,653, whose content is incorporated in the present description by reference. Each sensor is connected through a respective flexible duct43A,43B to a pervious needle45, one of which is visible inFIG. 4. The two needles45are carried by a slide47vertically sliding along guide columns49according to a movement f47imparted by an actuator, not shown. The lifting and lowering movement of the needles45integral with the slide47is used to make the two needles45penetrate in the test tubes P, which each time are located below the slide47. The lowering of the needles45is controlled in such a manner that the needles remain in the area of the single test tube P, in which is located the gaseous atmosphere, indicated with G inFIG. 4, without touching the biological sample C, e.g. a sample of urine, blood or other body fluid, collected in the lowest part of the test tube P. The lowering movement of the needles45causes the perforation of the caps T of the test tubes P, so that a part of the gas above the sample C can flow through the pervious needles45and the flexible ducts43A,43B, towards the sensors41A,41B of the analyzer13.FIGS. 4A and 4Bshow the penetration movement of the pervious needles45through the caps T of the test tubes P in order to position themselves (FIG. 4B) in the gas aspiration position. The gas in the single test tube P can flow through the respective duct43A,43B towards the sensor41A,41B due to the effect of the overpressure which generates inside the test tube because of the accumulation of carbon dioxide developed by the metabolism of the microorganisms, if any, present in the sample C.

The sensors41A,41B are able to detect the quantity of carbon dioxide present in the single analyzed test tubes with a precision sufficient for the purposes described below. A high precision, as well as a long or repeated detection are not necessary, as instead they are in the traditional systems, where the trend of the carbon dioxide concentration is used as significant parameter to determine the type of microorganism present in the sample. On the contrary, according to the present invention what is important is substantially the presence of carbon dioxide as an index of the metabolism of microorganisms present in the sample, whose nature will be determined, if necessary, in a subsequent phase of qualitative analysis carried out on the positive samples.

On the single test tubes P contained in the racks R the sorter15performs operations, which will be described below with specific reference toFIGS. 5 and 6, as a function of the carbon dioxide quantity detected by the single sensors41A,41B.

The sorter15provides to pick up the single test tubes P from the rack R which is fed in a stepped manner by the transferring unit31in order to sort them in the rest area11, or in a tray51below (FIG. 2) where the positive samples accumulate, or also to leave the negative samples in the rack R which is then taken by the operator and emptied of the test tubes P or simply ejected from the analyzing machine for a subsequent handling by the operator.

More in particular, in the illustrated embodiment the sorter15comprises a slide53guided on substantially vertical guides55and provided with a movement according to the double arrow f53(see in particularFIG. 3). Along the slide53a cursor59is movable along guides57, which carries a gripper61provided with an opening and closing element controlled by an actuator63carried by the cursor59. The cursor59is provided with a movement according to the double arrow f59(FIG. 3) along the longitudinal development of the slide53. Thanks to this double movement f59and f53, the gripper61can take single test tubes P from the rack R which is pushed in a stepped manner by the transferring unit31in order to discharge them through a well65in the space51below or to insert them in one or in the other of the two racks R which are in the rest area11.

It should be understood that the number of racks R in the rest area11can be different from that shown. For example, only one rack R can be provided, or more than two racks R, in which case the stroke of the gripper61with its cursor59in the direction f59will be obviously extended in an adequate manner so as to reach all the racks R arranged parallel in the rest area11.

FIGS. 5A-5Eshow the movement of the gripper61to discharge a test tube P+containing a positive sample (i.e. a sample in which there is such a bacterial load requiring a further analysis, for example through seeding, in order to detect the type of microorganisms present), through the well65in the space51below. InFIG. 5Athe open gripper is lowered towards the test tube P+which is above the gripper and which was carried in this position through a movement according to f31of the respective rack actuated by the transferring unit31. InFIG. 5Bthe gripper is lowered and is closed to engage the test tube P+. InFIG. 5Cthe test tube is lifted by extracting the test tube P+from the rack R so that with a movement according to f59the test tube is moved above the well65(FIG. 5B) where the gripper61opens in order to make the test tube P+fall in the well (FIG. 5E). Through the well, the test tube P+achieves a collection area, from where the operator will collect all the test tubes, which must be subjected to an analysis according to a known method, in order to detect the types of microorganisms present in the samples contained inside these test tubes.

When the sample in the test tube P which must be picked up by the gripper61is negative, i.e. when after the about 1 hour incubation in the incubation area7the analyzer41A or41B has not detected a significant carbon dioxide content in the atmosphere taken from the upper part of the test tube P, this test tube remains in the rack R and then passes, without being handled by the gripper61, beyond the position in which the manipulator15is located.

The samples for which in the inner atmosphere of the test tube a carbon dioxide content has been detected which is greater than a minimum value (below which the test tube is considered negative), but lower than a maximum value (over which the test tube is considered positive), are picked up by the gripper61and handled according to the cycle schematically illustrated inFIGS. 6A-6E. InFIG. 6Athe open gripper is ready to lower on the test tube indicated with P?, which must be subjected to a further incubation. InFIG. 6Bthe gripper has dropped and closed on the test tube P?. Then the gripper61provides to extract according to the arrow f53the test tube P?and to transfer it towards one of the racks R, which are in the rest area11with a movement which passes beyond the discharge well65as shown inFIGS. 6C and 6D. Once achieved this position, the gripper61is lowered to insert the uncertain test tube P?in the rack R of the rest area11(FIG. 6E), then it opens and lifts leaving the test tube in the rack, then returning in the gripping position for gripping a new test tube P contained in the rack R, which is fed in a stepped manner by the transferring unit31(FIG. 6F).

In this way in the racks R of the rest area11accumulate the single uncertain samples contained in the test tubes P?, whose carbon dioxide content is comprised between two rest values, minimum and maximum, and for these samples a further incubation is necessary.

In a modified embodiment, it is also possible to provide for all the uncertain samples to be subjected to a further analysis in order to detect the type of microorganisms contained inside them, thus not providing for the rest area11, or leaving it inactive and sorting the test tubes simply by subdividing them into positive and negative, thus discharging the uncertain samples according to the procedure described above directly in the well65together with the positive samples. It is also possible not to provide for the discharge well, and to transfer the positive and uncertain samples in the area11, from where they are manually picked up for a seeding process or other procedure for the detection of the pathogenic microorganisms inside them, whilst on the original racks R coming from the first incubation area the test tubes with the surely negative samples remain.

According to further embodiments, it is possible to put the negative samples in the discharge well, so that no test tubes remain on the racks R coming from the incubation area. In a further variant of embodiment, the surely negative samples can be transferred in the rest area11, the surely positive samples can be discharged through the well in the area below and the uncertain samples can remain in the rack in order to be inserted in the load area again.

What is important is, substantially, the fact that a sorting is carried out at least between positive test tubes and negative test tubes, and preferably between positive test tubes, negative test tubes and uncertain test tubes, these latter being subject to a second incubation phase.

According to some embodiments, in the rest area11incubation means can be provided, so that the uncertain test tubes P+are maintained in conditions of incubation at a controlled temperature, for example about 37° C., directly in the rest area11and from here they are handled in the way described above, providing for example a second analyzer in the rest area11, or transferring the single racks from the rest or second incubation area11to the area in which the sensor41A,41B are active.

However, according to the preferred embodiment, the racks R, which have been filled in the rest area11, are picked up by the operator, who inserts them again in the load area3so that they can be subjected to a new incubation cycle in the incubation area7.

In order to allow the uncertain samples contained in the test tubes P (P?) of the rest area11to develop the metabolism of the microorganisms present there, according to some embodiments in the rest area11a device can be provided, generically indicated with the number71, which injects oxygen or in any case a gas containing oxygen in the single test tubes P, which are in the rest area11. The device71can comprise for example a slide73vertically movable along guide columns74and carrying a pair of pervious needles75A,75B which can perforate the test tubes P which are in the rest area11and insufflate inside them oxygen or ambient air, fed for example by a compressor connected to the needles75A,75B by means of flexible ducts. Feeding of the racks R in the rest area11in order to allow their filling with the uncertain test tubes P?and their perforation passing through the device71is obtained for example through two transferring members81A,81B with a conformation substantially equal to that of the transferring units21,31and not described in greater detail.

In this way the single racks R are gradually filled with the uncertain test tubes P?passing below the slide53and carry each test tube P below the needles75A,75B so as to make the test tubes receive oxygen that can develop the metabolism of the microorganisms and thus push the racks R outside the rest area11in order to allow their re-introduction in the load area3.

The device will be provided with a user interface which allows to communicate to the central unit of the machine which racks R inserted in the load area3have already undergone a first incubation phase, and thus contain uncertain test tubes, and which are loaded with new test tubes on which the first incubation in the area7must be carried out.

In this way the machine, being provided with encoders associated with all the actuators for handling the racks through the different areas of the machine, can know in any instant what rack contains test tubes already undergone a first incubation and now in phase of second incubation, and what racks contain test tubes which must be subjected to a first incubation, the analysis and a second incubation, if necessary, if the test tubes result to be uncertain. Alternatively, instead of following the single test tubes with a control of the feeding movements, it is possible to provide a system for reading bar codes or other codes associated to the test tubes, to recognize each test tube in the essential points of their path through the machine.

The test tubes containing uncertain samples (test tubes P?) coming from the rest area11, once they have been subjected to a second incubation phase in the incubation area7(or, in a modified embodiment, directly in the rest area11), are subjected to a new analysis through the analyzer13. The carbon dioxide content detected during this second analysis is compared preferably with a single threshold value. The samples containing a carbon dioxide quantity greater than the threshold value are considered positive, and thus discharged through the sorter15in the well65, whilst the samples containing a carbon dioxide quantity lower than this threshold value are considered negative and remain in the rack, which is gradually ejected from the area7due to the effect of the transferring unit31.

The threshold used for the discrimination following the second incubation can be equal to the minimum threshold or to the maximum threshold used for sorting and discriminating the test tubes, which underwent a first incubation phase.

The entire process is schematically summarized in the flow chart ofFIGS. 8A,8B. The flow chart indicates how the single test tube is filled with the sample to be analyzed and then inserted in the device. Subsequently the test tube is subjected to incubation for a period ΔT and, once the incubation ended, the atmosphere from the test tube is removed. The detected carbon dioxide quantity is compared with a first threshold Smaxand a second threshold Smin. If the carbon dioxide content is greater than the threshold Smaxthe sample is considered positive and discharged, by the sorter15, through the well65in the space51below. If the carbon dioxide quantity is lower than the threshold Sminthe sample is considered negative and kept in the rack, and then it is ejected from the machine. If neither one or the other of the two conditions occurs, and thus the carbon dioxide content is comprised between Smaxand Smin, oxygen is added in the test tube to allow the prosecution of the metabolism and a second incubation is performed for a time interval that in this example lasts for a time ΔT equal to that of the first incubation, although this is not strictly necessary, a different duration for the two incubation phases being possible. Once the second incubation is ended, the atmosphere is removed from the test tube and the carbon dioxide content is compared with a single threshold, which in the illustrated example is the threshold Smax, but which may be equal to the threshold Sminor to a threshold different from the thresholds Smaxand Smin. If the sample has developed a carbon dioxide quantity greater than Smaxit will be considered positive, otherwise it will be considered negative.

In order to optimize the incubation of the samples, according to some embodiments in the incubation area7agitating members are provided, positioned in an adequate manner along the feed path of the racks. These agitators are not shown inFIGS. 1 to 6in order to simplify the drawing, but one of them is schematically represented inFIG. 7below a single test tube P. The agitator ofFIG. 7is generically indicated with the number100. It comprises an actuator101, for example an electric motor, which puts in rotation a magnetic element103, for example a magnetic bar inserted inside a disk keyed onto the shaft of the motor101. The magnetic element103acts as a magnetic carrier for an agitating element107contained in the test tube P and drowned in the sample C, which is in the same test tube P. The magnetic coupling between the element103and the element107causes, due to the effect of the rotation of the shaft101, the rotation of the element107. This latter can be adequately shaped, for example with fins, to create a possible upwards movement of the sample C contained in the test tube P to optimize the incubation conditions thereof inside the test tube P, in which also the growth medium is contained.

FIG. 7schematically shows also a further possible feature of the device according to the present invention, constituted by a sensor generically indicated with111and suitable to detect the level of the sample C inside the test tube P. The sensor111can be a capacitive sensor or a sensor of any other type. For example it can comprise an emitter/receiver device to detect the level of the sample C by transparency. The sensor111can be provided with a vertical movement parallel to the axis of the test tube P in order to detect the level of the sample C in the test tube. The sensor111can be arranged in any adequate position inside the device1, for example in the free area between the load area3and the incubation area7, as schematically indicated with111inFIG. 1, so as to determine the level of the sample in each single test tube during the transfer of the test tubes contained in the racks R performed by the transferring unit1from the loading area3to the incubation area7.

Determining the level of the sample C in each test tube P allows avoiding the accidental immersion of the tip of the needles or cannulas45inside the biological sample, as this circumstance can damage the sensors41A,41B. The central control unit of the machine can store the level of the sample C detected in each test tube P so as to allow the lowering movement of the slide47, which carries the needles45, to be always sufficient to perforate the caps T of the test tubes P, but such that the needles do not come into contact with the sample.

With the method and the equipment described above it is possible to sort a high number of samples contained in test tubes P after a first incubation period (for example about one hour), sorting them into surely positive sample, surely negative samples and uncertain samples, if any. These latter can be considered positive for safety and simplicity, or they can be subjected to a second incubation cycle and thus to a second sorting between positive samples and negative samples according to a method schematically summarized in the flow chart ofFIGS. 8A,8B. Finally, independent of the method chosen, after a period of max. two hours it is possible to obtain from a high number of samples a first sure result on surely negative samples and a significant reduction of the samples which must be subjected to a longer and more accurate analysis, for example through seeding, to detect which microorganisms are there inside the samples classified as positive. Therefore, only these samples will be subjected to seeding or other analysis with a considerable saving in costs and risks.

This allows to obtain substantial advantages with respect to all the traditional methods of analysis, in particular those described in the patent documents mentioned in the introductory part of the present description.

In order to automate the analyses carried out by the device described above, it is possible to provide that the single test tubes P are marked in the production phase with a univocal code. Each test tube will be furthermore provided with a label, a band or the like, carrying a code, for example in the form of a bar code, connected in a bi-univocal manner to the data of the patient to whom the sample C contained in the test tube pertains. The equipment1can be provided with a bar code reader or the like, which reads the univocal code applied to the test tube in the production phase and the code related to the patient to whom the sample contained in the test tube belongs. These two codes are matched by the central unit of the equipment1, so that the code related to the patient, applied for example by means of a band around the cap of the test tube P, can be subsequently removed in order to facilitate the analysis operations on the samples deemed positive. These analyses, for example seeding, in fact require the breakage of the test tube and thus the risk of damage to the bar code, which identifies the patient and is applied on the cap. The matching between code of the test tube and code of the patient, carried out by means of the reader associated to the device1, avoids the risks of loss of the data of the patient to whom the sample belongs, when the test tube is broken to perform seeding.

Subsequent analysis operations are performed automatically, by storing the identification code of the test tube which matched in a one-to-one manner the patient code and associating the result of the analysis with the code of the test tube. Once the analyses have been performed and the result obtained, these can be matched again to the data of the patient simply recovering the data through the identification code of the patient and the identification code of the test tube mutually associated.

It is understood that the drawing only shows an example provided by way of a practical arrangement of the invention, which can vary in forms and arrangements without however departing from the scope of the concept underlying the invention. Any reference numbers in the appended claims are provided for the sole purpose of facilitating reading of the claims in the light of the description and the drawing, and do not in any manner limit the scope of protection represented by the claims.