JPS63189152A - Sterilization method by radiation - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial application field The present invention is applicable to general miscellaneous goods, agricultural and marine products, processed animal and plant products, minerals,
The present invention relates to a method for sterilizing polymeric materials, fibers, paper products, foods, feeds, medical tools, pharmaceuticals, and similar products using radiation. As the radiation, X-rays, gamma rays, electron beams, etc. can be used. The targets of sterilization are general microorganisms such as bacteria, filamentous fungi, and yeast, as well as viruses. Examples of miscellaneous goods include tatami mats, carpets, cloth, wooden products, feathers, futons, clothing, baby products, beds, sanitary products, woolen fabrics, hospital supplies, food packaging materials, medical containers, art and antiques,
Examples include books, bed food, and soil for vegetable gardens.

Conventional technology Currently, items that are practically treated with radiation include feed for laboratory animals, medical tools, and various packaging materials.

Conventional irradiation is currently carried out at room temperature and humidity, assuming that the irradiation temperature and humidity do not have a significant effect on the sterilizing effect when processing at room temperature. For example, when sterilizing medical equipment, the dose is calculated using the following formula.

Germicidal radiation m-DXΩog (No/N) D; D value of indicator bacteria (dose at which the number of viable bacteria becomes 1/10) No; Number of contaminated bacteria before irradiation of the irradiated object N; After irradiation of the irradiated object The number of contaminating bacteria This D value is usually determined by Bacll, which is used as an indicator bacteria.
t, ykcy of P. lus pumilus E601 is used, and a sterilizing dose of 25 kGy is generally adopted in many cases.

Problems to be Solved by the Invention Although sterilization treatment using radiation is progressing worldwide, it cannot be said that there are necessarily many objects to be irradiated.

In fact, although there is a need to irradiate miscellaneous goods, the current situation is that it is not being carried out. The reason for this is that the equipment investment is large, the irradiation cost is high, and the quality of some objects may deteriorate. For this reason, even today, we have no choice but to rely on complicated and highly dangerous fumigation treatments. Currently, EO (ethylene/oxide) is generally used as a fumigant, but there are problems with the fumigant and its decomposed products remaining in the object to be treated, and safety and health problems for workers.

Under these circumstances, there is a desire to develop processing techniques to suppress quality deterioration and reduce irradiation costs.

These problems of quality deterioration and irradiation cost can be solved by finding ways to reduce the sterilization dose.

Until now, physical means to reduce the sterilization dose have been considered, such as combining heating to 52° C. or higher or high-pressure treatment. However, high-pressure treatment is complicated and expensive, and methods in combination with heat treatment have the disadvantage that there are large variations and that stable effects cannot be expected. On the other hand, the most effective way to prevent quality deterioration is to remove oxygen from the atmosphere, but removing oxygen reduces the radiation sensitivity of microorganisms, resulting in an increase in the sterilization dose. .

Means for Solving the Problems In order to develop a processing method that prevents quality deterioration and reduces sterilization doses, the present invention examines in detail the effects of humidity and atmosphere, which were previously thought to have little effect. As a result of our investigation, we found irradiation conditions and a method to reduce the sterilization dose in a stable state with little variation, and completed a method that can be applied to objects that could not be treated before.

The temperature of the object to be processed, its surroundings, or the processing chamber is set to 25
By maintaining the temperature at ~60°C and the humidity in the range of 55 to 65% with a center of 58%, and by maintaining the object to be treated or its surroundings in a nitrogen gas atmosphere, quality can be achieved at 1/2 to 1/3 of the conventional dose. The purpose of irradiation treatment can be achieved without deterioration. However, for objects where quality deterioration is not a problem, it is not necessary to maintain a nitrogen gas atmosphere.

Effects of the Invention The radiation treatment performed under the conditions specified in the present invention reduces the sterilizing dose of the object to be treated and minimizes quality deterioration, thereby providing the following effects.

(1) Significant reduction in irradiation costs (2) Reduction in radiation source and equipment investment (3) Achievement of stable irradiation (4) Expansion of irradiation targets This is unprecedented, and the effects of the present invention are extremely large.

Examples Examples of the present invention are shown below. These tests were carried out using a 160,000 curie cobalt-60 gamma irradiator and a 3MV
This was done using an electron accelerator. In addition, the radiation sterilization effect is due to B. pumillus, which is an indicator bacterium for sterilization of medical tools.
Washed spore bacteria of E601 were vacuum-dried on a glass filter or in a sample and irradiated under various conditions and observed.

Example I B, 2 x 107 spores of pumilus E801
φ was applied directly to the syringe barrel, dried in a silica gel desiccator for about a week, and then placed in a constant temperature container containing various salt-saturated solutions to adjust the humidity so as not to come into contact with the salt solution. The entire container was sealed. After keeping the container at 25° C. for about 1 day to equilibrate the humidity, the temperature was adjusted to each temperature 30 minutes before irradiation and irradiation with gamma rays was performed.

As shown in Figure 1, the sterilization effect increases as the temperature increases at a humidity of 58%, and at 50"C, the sterilization effect increases at 0℃
Approximately 4 orders of magnitude more sensitization than in the case of . On the other hand, in the case of 40°C, sensitization of 2 to 3 orders of magnitude is observed at 80 to 90% humidity, but it is extremely unstable and is not suitable for the purpose of controlling the increase in bactericidal effect using humidity. Not suitable. The humidity of 58%, which increases the sterilizing effect, has the advantage that dry objects can be processed without getting wet.

Example 2 The same spore bacteria as in Example 1 was dried on a glass filter,
Fix it inside the top lid of a Petri dish, put a salt saturated solution inside the Petri dish and seal it to create humidity of 53% and 58%, and set the temperature to 25%.
irradiated with an electron beam at °C. The irradiation conditions were IMeV, 0.
At 5 mA and a conveyor speed of 2.02 m/a+in, the dose is 6 kGy.

The survival rate at 58% humidity is 3 x 10-5 and 53
The survival rate in % was reduced by about one order of magnitude compared to 4X10'. As shown in this figure, it was confirmed that electron beams have a greater bactericidal effect at 58% humidity, similar to gamma rays.

Example 3 Under the same conditions as Example 1, N2 gas was blown into the constant temperature container for 5 minutes, N 2 gas was blown into the thermostatic container after it was evacuated, and 02 gas was blown into the container for 5 minutes. They prepared objects, irradiated them with gamma rays, and investigated the effect of the atmosphere during irradiation.

As shown in Figure 2, the sterilization effect worsens when N2 gas is blown into the room after being evacuated, but the sterilization effect obtained when only N2 gas is blown in shows the same sterilization effect as air or 02 gas injection. . In Table 1, in addition to B. pumilus, B. 5ub
13-
There is no change in the sterilizing effect of Bacillus subtilis spores other than pumilUS between injecting N2 gas and air.

Table 16 Survival rate of various Bacillus subtilis spores in N2 injection and in air (8,8 kGy) and their ratio B, 5abtil
is 1. I Xl0-41 Xl0-' 1.
1B, 11cheniformis 1.5 As shown in FIG. 3, compared to irradiation in air, the reduction in breaking strength is smaller when N2 gas is injected, and quality deterioration can be significantly suppressed just by injecting N2 gas.

As is clear from the above examples, the method described in the claims can be used to reduce the oxygen concentration in the atmosphere simply by venting N2 gas, and to reduce the temperature to 25 to 50°C and the humidity to 58%. It has become clear that by maintaining the sterilization effect in the range of 55 to 65%, the bactericidal effect can be increased by 2 to 3 times compared to the conventional one while suppressing quality deterioration.

[Brief explanation of the drawing]

FIG. 1 shows the effects of irradiation temperature and irradiation humidity in radiation sterilization. Figure 2 shows the results of radiation sterilization in dry N2 and air (
This is to demonstrate the bactericidal effect at room temperature. FIG. 3 shows the degree of deterioration of polypropylene in nitrogen gas and air during radiation sterilization.

Claims (1)

[Claims] 1. Maintaining the temperature of the dry object to be processed, or the surroundings of the object and the processing chamber, at 25 to 50°C, and the humidity in the range of 55 to 65%, centered around 58%. A radiation treatment method characterized by increasing the sterilizing effect of the object to be treated. 2. By keeping the dry object that is susceptible to quality deterioration due to radiation treatment in an atmosphere by blowing N_2 gas, and keeping it at a temperature of 25 to 50 degrees Celsius and a humidity range of 55 to 65%, A radiation treatment method characterized by preventing quality deterioration and increasing sterilization effect.