JPH0492671A - Sterilizing method for petri dish made of synthetic resin for culture medium - Google Patents

Abstract

PURPOSE:To surely execute the sterilization, and also, to execute the sterilization at a low cost by irradiating a Petri dish made of synthetic resin for a culture medium with an electron beam. CONSTITUTION:A Petri dish made of a synthetic resin for a culture medium is irradiated with an electron beam. The irradiation of the electron beam is executed by an electron beam accelerating device. The electron beam accelerating device concerned is not specifically limited in so far as it emits an electron beam of high energy. In this case, the electron beam being a main body for executing a sterilizing action can be managed by setting values of a voltage and a current, therefore, the sterilization management is facilitated. In such a way, the sterilization time can also be shortened, and also, the Petri dish made of a synthetic resin for a culture medium can be sterilized at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for sterilizing a synthetic resin petri dish for a blood agar medium, a tissue culture medium, a synthetic medium, or the like.

(Prior art and its problems) Conventional methods for sterilizing synthetic resin petri dishes for culture media include EOG sterilization using ethylene oxide gas (hereinafter referred to as rEOGJ) and γ-ray sterilization using γ-rays, which is a type of radiation. Ta.

On the other hand, blood agar medium is a medium in which blood is mixed into an agar medium, dispensed and coagulated, and it is very difficult to see whether the suspended red blood cells in the medium will hemolyze during bacterial culture. Therefore, if red blood cells become hemolyzed or discolored during storage of the blood agar medium in a petri dish, the commercial value will be lost.

The above-mentioned conventional EOG sterilization has problems in that the gas used may remain in the petri dish, even if only a small amount, and microorganisms may remain even after treatment.
When using petri dishes for blood agar media, there are problems in that the culture medium deteriorates over time, such as hemolysis and discoloration, and the growth support ability of the culture medium decreases over time.

In addition, the conventional gamma ray sterilization described above has a large effect on the physical properties of the Petri dish itself, causing discoloration, making it troublesome to manage and maintain the gamma ray source, requiring a long sterilization time, and reducing the need for shielding. However, there were issues such as the high cost involved.

The present invention has been made in view of the above-mentioned problems in the prior art, and has been made to solve the problems.
Another object of the present invention is to provide a method for sterilizing a synthetic resin/yare medium for use in a culture medium that prevents or suppresses changes over time and decline in growth support ability over time and can be sterilized at low cost.

(Means and effects for solving the problems) According to the present invention, the above-mentioned problems can be solved by a method of sterilizing a synthetic resin petri dish for culture medium, which is characterized by irradiating the synthetic resin petri dish for culture medium with an electron beam. is solved and the above objectives are achieved.

That is, by using the method of the present invention, germs, microorganisms, etc. attached to the synthetic resin/yellow material are annihilated in a short time by irradiation with electron beams, and the irradiated electron beams do not remain.
Moreover, it has little effect on the physical properties of the synthetic resin petri dish itself.

The material for the synthetic resin Petri dish for the culture medium used in the present invention is not particularly limited as long as it is a transparent synthetic resin, such as polystyrene, AS resin, ABS resin, polyethylene, polypropylene, acrylic resin, and polyethylene terephthalate.

It can be polycarbonate resin, methylpentene polymer polysulfone, polyamide, polyacetal, polyester, vinyl chloride resin, etc.

Further, the electron beam irradiation in the present invention is performed by an electron beam accelerator. The electron beam accelerator is not particularly limited as long as it emits a high-energy electron beam.
For example, Dynamidron (massage chamber) manufactured by Sumitomo Heavy Industries, Ltd. is used.

The electron beam accelerator is capable of steplessly setting acceleration energy from 0.5 MeV to 5 MeV, and is configured to irradiate the workpiece being transported by a cart conveyor with an electron beam of the above energy. be.

In addition, the optimum electron beam irradiation dose for sterilizing the synthetic resin/yellow material for this culture medium is preferably 5 kGy to 150 kGy, and irradiation with more than 150 kGy is preferable because discoloration of the synthetic resin/yellow material will occur. , not. Also,
If there are few germs, microorganisms, etc. adhering to a synthetic resin Petri dish, sterilization can be achieved by irradiation with IkGy, but in reality it was necessary to irradiate with 10kGy or more.

(Example) Next, the present invention will be explained in further detail using an example as a comparative test example. In addition, in this comparative test example, a case will be described in which a blood agar medium is used as the medium, but it should be noted that it is similarly applicable to tissue culture medium, synthetic medium, etc.

Electron beam sterilization according to the present invention / EO according to Yare and conventional technology
The effect on the shelf life of the blood agar medium was tested using G sterilized Petri dishes.

(1) Sterilization method - Electron beam sterilization petri dish Place the polystyrene petri dish in a cardboard box and use an electron beam accelerator (Dynamidron-rubbing room) to increase the acceleration energy of the electron beam to 5 MeVX I[imA and the speed of the cart conveyor to 5 m. /min, and an electron beam was irradiated from the outside of the cardboard box to both sides of the petri dish inside the box. The electron beam irradiation dose was ff5.8 kGy for the petri dish at the side of the cardboard box, and 13.9 kGy for the petri dish at the center of the cardboard box.

■ Prepare a gas mixture of 20% EOG sterilized petri dish and 80% carbon dioxide,
It was sent to a polystyrene petri dish under a pressure condition of 0.35 kg/am2, sterilized by aeration at a temperature of 35 to 50 °C for 4.5 to 5.0 hours, and then the air ray/yon was sterilized for 15 to 2 hours.
This was done 3 times for 0 minutes.

(2) Test method The performance test and appearance test described below were conducted using the electron beam sterilization/Yare obtained by the above sterilization method and the EOG sterilization/Yare.

■Performance test: 12 electron beam sterilized Petri dishes and 12 EOG sterilized Petri dishes each.
Of these, sheep blood agar medium was placed in each of five sterilized petri dishes, and horse blood agar medium was placed in each of the remaining seven sterilized petri dishes. Next, while maintaining 7 volumes of each of the above blood agar media at 10°C, changes over time in the blood agar media after 3 weeks were examined. Each of the above 5
Four of the four Petri dishes containing sheep blood agar medium were inoculated with a strain of Streptococcus group A, and the remaining one Petri dish was inoculated with a strain of Streptococcus pneumoniae. In addition, five of the seven petri dishes containing horse blood agar were inoculated with Streptococcus strains in the same manner as above, and the remaining two dishes were inoculated with Haemophilus.
Inoculated with influenza strains (each of the above strains was
(cultured at 37°C for 20-22 hours). The results are shown below in Table 1 and Table 2, 3rd column: Hemolytic ring diameter (+nm) Bacterial strain; 1-4: 5: Streptococcus Streptococcus Group A pneumonia Table 2 ■Performance test results Table 1 and above As is clear from the results in Table 2, the electron beam sterilization/Yahle according to the present invention and the EOG sterilization/Lehle according to the prior art are the most significant and important features of blood agar media, such as β-hemolysis of Streptococcus group A. Performance”.

“α-hemolytic performance of Streptococcus pneumoniae”
Significant differences were observed in the effects on maintenance.

That is, immediately after production, there was no difference in performance between the two blood agar media using the Noyale sterilization method.

However, when the above-mentioned strain was inoculated and cultured after 2 months and 3 weeks, β-hemolysis of Streptococcus A group 1 to 4 was found to be γ in blood agar medium using EOG sterilized petri dish and blood agar medium immediately after production, which is a control medium. Hemolysis (non-hemolysis) occurred, the hemolysis ring became smaller, and the settlement became smaller. Similarly, the α-hemolytic ring of Streptococcus pneumoniae strain 5 became smaller and the colonies became smaller. Furthermore, the colony of Haemophilus influenzae strain 6.7 was also smaller. On the other hand, when an electron beam sterilized petri dish was used, even after storage for the above period, there was no significant difference from the blood agar medium immediately after production. Therefore, it has been found that the electron beam sterilization method according to the present invention is significantly superior to the EOG sterilization method according to the prior art.

■Appearance test Electron beam sterilized Petri dishes and EOG obtained by the above sterilization method
Prepare 4 sterile Petri dishes, and put sheep blood agar medium in 2 sterile Petri dishes to make lOoC and 1.
The remaining two sterilized petri dishes were kept at 10°C and 15°C with horse blood agar medium placed in each of the remaining sterilized petri dishes. The color change over time of each blood agar medium in a petri dish was measured using a color difference meter. This measurement was performed by bringing each blood agar-filled Petri dish from storage temperature to room temperature, and then heating it for 37 hours.
This was done after being left at °C for 24 hours. In addition, this measurement was performed using a CM100OJ color difference meter manufactured by Minolta Co., Ltd. This color difference meter analyzes reflected light and digitizes the color tone. r
The L-value (lightness) and the a-value (redness) are important, and both serve as indicators of the degree of hemolysis and blackening. Due to hemolysis or blackening, the ° value and a value described above decrease.

The color change over time of each blood agar medium in a petri dish measured by the color difference meter is shown in FIGS. 1 to 4, with the horizontal axis representing the number of months that have passed and the vertical axis representing the a° value.

■Appearance test results and discussion As shown in Figures 1 and 2, a sheep blood agar medium placed in an electron beam sterilized petri dish can be stored for 3 months even if stored at 10℃ or 15℃. It was found that almost no hemolysis Φ discoloration occurred; on the other hand, in the case of sheep blood agar culture medium placed in a petri dish sterilized with EOG, it was stored for about 2 months at 10°C and after about 1 month when stored at 15°C. It was found that discoloration occurs relatively rapidly during hemolysis, and in particular, the higher the storage temperature, the more rapidly hemolysis occurs.

Regarding the horse blood agar medium, as shown in Figures 3 and 4, hemolysis and discoloration occur earlier than in the case of the sheep blood agar medium shown in Figures 1 and 2; The degree of hemolysis and discoloration over time of the medium placed in a line-sterilized Petri dish is much lower than that of the medium placed in an EOG-sterilized Petri dish, and it hardly depends on the storage temperature.
It was found that the degree of hemolysis and discoloration of culture media placed in sterilized petri dishes increases significantly over time if the storage temperature is high. Also, L.

The value also changed almost in the same way as the a value.

■If the sterilization method for synthetic resin petri dishes for comprehensive evaluation media is changed from EOG sterilization to electron beam sterilization, the storage period of sheep blood agar and horse blood agar can be effectively extended.

(Effect of the invention) According to the method of the present invention, the effects described below are brought about.

(1) In the method of the present invention, sterilization is easy because the electron beam, which is the main body that brings about the sterilization effect, can be controlled by setting the voltage and current values, and the sterilization time is also significantly shorter than that of conventional gamma ray sterilization. It is possible to sterilize synthetic resin/yare for culture medium in short time and at low cost.

(2) According to the method of the present invention, when storing a culture medium using the sterilized petri dish, there is significantly less change (deterioration) over time (therefore, the ability to support growth over time) compared to the conventional EOG sterilized medium. The decrease can be prevented or suppressed.

[Brief explanation of drawings]

FIGS. 1 to 4 are graphs showing changes in color tone over time of a sheep blood agar medium and a horse blood agar medium in a Petri dish, respectively. Patent Applicant Nisui Seiyaku Co., Ltd. Figure 1 Sheep Blood ) Etsutsutsuki Figure 2 Sheep blood 11 prefectures Inusaihi (15 degrees Celsius left) EOGi relative Tsun Schiele, Zegastric Figure 4, 5M] J tatami! 14 words and 3 letters (15°C)

Claims (1)

[Claims] (1) A method for sterilizing a synthetic resin petri dish for a culture medium, which comprises irradiating the synthetic resin petri dish for a culture medium with an electron beam.