There have usually been used a plastic microplate provided thereon with a plurality of wells as a reaction vessel or a culture vessel in a chemical test which comprises a process for reacting a chemical sample with a certain reagent, or a microbiological test which comprises a step for cultivating a microorganism in a sample, in particular, in a test which requires treatments of a number of samples, reactions with a number of reagents or cultivation of a microorganism in a number of systems.
For instance, a plastic plate equipped with a number of small wells has usually been used in immunological assays such as ELISA assays. In respect of the determination of the sensitivity of bacteria to antibacterial agents by the micro liquid dilution technique, i.e., the determination of the minimum inhibitory concentration (MIC) for a specific antibacterial agent, there has widely been used the single disc method according to the agar plate dilution method or the agar diffusion method, but the use of a microplate provided with U-shaped wells identical to that used in the immunological tests is specified, in the standard method for the determination of MIC by the micro liquid dilution technique which is designated by the Chemotherapeutic Association of Japan in 1989, which is similar to the foregoing single disc method further economized and automated.
In such a test wherein a microplate is used, individual reactions or cultivation of microorganisms each is carried out in a separate well on the plate. In the determination of MIC by the micro liquid dilution method using a microplate, for instance, an antibacterial agent is added to a plurality of wells in a variety of concentrations and the growth of a bacterium to be tested in each well is then observed to thus determine the minimum inhibitory concentration of the antibacterial agent. As microplates used in such tests, there have been put on the market one which is prepared by preliminarily dispensing a desired amount of an antibacterial agent to each well and then drying or freezing and storing. However, the microplate per se is expensive, this makes it difficult to offer a cheaper commodity and accordingly, the users have strongly desired for the reduction of the price thereof. Moreover, such a microplate requires the dispensation of a desired amount of, for instance, a liquid sample to each well during testing and it requires a tremendous labor to carry out the test. Accordingly, it is preferred to develop an instrument for easily dispensing, for instance, a desired amount of a liquid sample to a container used for carrying out the desired test.
To meet such a demand, the inventors of this invention have proposed an instrument for use in chemical tests or microbiological tests, which comprises a base provided thereon with portions for holding a sample (WO 94/04703). The instrument is designed to absorb, for instance, a liquid sample in the sample-holding portion formed on the base to hold a desired amount of the liquid sample on or within the sample-holding portion and to thus meet the foregoing requirement. To allow the instrument to hold a sample, however, it should be designed in such a manner that an excess of the sample is dropwise added to the instrument and then it is, for instance, inclined to remove the excess sample; or the instrument per se is immersed in a liquid sample accommodated in a container and then pulled up to thus allow the sample-holding portion to hold a desired amount of the sample.
For this reason, the liquid sample is inevitably scattered in the surrounding to some extent when using the foregoing instrument to carry out such a test. However, any scattering of the liquid sample should sometimes be avoided when the liquid sample to be tested comprises, for instance, pathogens.