Sterilization effect of Co60 γ rays
Diets/Radiation-sterilized Diets/
Sterilization effect of Co60 γ rays
1.Radioresistance of microorganisms
Shibasaki Isao : Topics of radiation sterilization techniques.
Seiyaku Kogyo (Pharmaceutical Industry) Vol.5,No.7,1985
Seiyaku Kogyo (Pharmaceutical Industry) Vol.5,No.7,1985
| Microorganisms | Does (kgy) required to cause a decrease to 106 cells |
|---|---|
| Gram-negative microbes | |
| Escherichia coli | <0.5~ 3.0 |
| Proteus vulgaris | <0.5~ 1.5 |
| Salmonella typhi | <0.5~ 5.0 |
| Shigella dysenterae | 2.0~ 3.0 |
| Pseudomonas aeruginosa | <0.5~ 2.0 |
| Gram-positive microbes | |
| Bacillus subtilis spores | 10.0~ 20.0 |
| Baci. cereus spores | 20.5~ 30.0 |
| Crosridium perfrigens spores | 20.0~ 30.0 |
| Staphylococcus aureus | <0.5~5.0 |
| Micrococcus radiodurans | >30.0 |
| Molds | |
| Aspergillus niger | 3.0~ 5.0 |
| Asp. flavus | 2.0~ 3.0 |
| Penicillum notatum | 1.5~ 2.0 |
| Yeasts | |
| Candida albicans | 7.0~ 10.0 |
| Can. Krusei | 10.0~ 20.0 |
2.Dose required for the sterilization of radioresistant microbes
Saito Muneo : Application of radiation-sterilized diets for germ-free of SPF animals.
Radiation & Industries No.24,1984
Radiation & Industries No.24,1984
| Test groups | Treatment | Irradiation does of Co60γ rays (kGy) | ||||||
| No irradiation | 10 | 20 | 30 | 40 | 50 | 60 | ||
| Resisttant microbe groups※ | M | ー | ー | 26/40 | 18/40 | 1/40 | 0/40 | 0/40 |
| M+B | ー | ー | ー | 25/50 | 8/50 | 0/50 | 0/50 | |
| B | ー | ー | ー | ー | 0/40 | 0/40 | 0/40 | |
| Control | No treatment | 50/50 | 8/50 | 0/50 | 0/50 | 0/50 | 0/50 | 0/50 |
M = Micrococcus radiodurans (radioresistant bacterium)
B=Bacillus cereus (radioresistant bacterium)
The figures in the table denote the number of samples with surviving bacterial cells/the number of tested samples.
*In the resistant microbe groups, the respective bacterial cells were infused into a hole 2 mm in diameter made in the central part of each CL-2 pellet.
3.Results of sterilization tests of products
Samples of diets for germ-free animals and SPF animals were extracted randomly for each irradiation dose and tested for sterility by culture examination for aerobes, anaerobes, and fungi. The results were all negative.
| '87 | '88 | '89 | '90 | '91 | '92 | '93 | '94 | '95 | Total | |
| 50kGy | 0/ 5 | 0/ 6 | 0/ 4 | 0/ 5 | 0/ 7 | 0/ 4 | 0/ 0 | 0/ 3 | 0/ 1 | 0/ 35 |
| 30kGy | 0/33 | 0/62 | 0/80 | 0/62 | 0/75 | 0/54 | 0/54 | 0/73 | 0/78 | 0/553 |
| 20kGy | 0/ 8 | 0/14 | 0/15 | 0/17 | 0/15 | 0/17 | 0/ 8 | 0/21 | 0/16 | 0/131 |