STUDIES ON THE DOSE REQUIREMENT FOR THE RADIATION STERILIZATION OF MEDICAL EQUIPMENT. I. INFLUENCE OF SUSPENDING MEDIA
Studies were designed to establish whether the efficiency of sterilization by radiation is affected by the nature of the materials being treated and the environment in which contaminants might be present. Spores of Bacillus pumilus were used since their radiation resistance is comparatively high, and data are presented for comparison of the radiation resistance of these spores dried in air from various media on to different surfaces. The media (buffer, nutrient broth, and serum) were chosen as representative, respectively, of inorganic, organic, and biological materials. Comparisons were made between several insoluble supporting surfaces, e.g., glass and polymethacrylate (Perspex), and a soluble surface in the form of polyvinyl alcohol (PVA) film. The results were compared with those obtained when the spores were suspended in buffer solution or nutrient broth under both aerated and anoxic conditions. Radiation from a /sup 60/Co source was used at a dose rate of 2.4 x 10/sup 5/ rad/ hr. The D values (the dose required to reduce the number of survivors to 1/10, i.e., 90% kill) were calculated directly from the linear part of survival curves. The D values for dried spores fall into two groups. First, spores dried from buffer, nutrient broth, or serum on to the insoluble surfaces behaved in a very similar manner, and the D values are of the same order as those obtained in liquid suspension in buffer and nutrient broth under aerated conditions; these were 0.175 (0.169to 0.180) and 0.169 (0.162to 0.177), respectively, (95% confidence limits in brackets). The efficiency of the radiation was not affected by changes in the degree of hydration of the spores corresponding to air-dry or aqueous conditions. However, at lower hydration levels, increase in lethal efficiency was demonstrated. Second, with each of the suspending media dried on to the soluble surface (i.e., PVA film) a comparatively higher D value was obtained; spores dried from PVA solution on to insoluble surfaces gave a similar result. The increase in resistance might to some extent be due to chemical protection, but is most probably mainly due to local anoxic conditions produced as a result of the spores being trapped in the film during drying. This situation is most likely to arise from PVA solution dried on to the PVA film, which gave the highest D value. The results compare with those obtained for suspensions in buffer, nutrient broth, and 2% (w/v) aqueous PVA under anoxic conditions; these were (0.322 to 0.349), respectively. It is concluded that for practical purposes of radiosterilization the radiation resistance of air-dried spores is independent of the media from which they are dried (PVA as a suspending medium presents an artificial situation) and is not influenced by the supporting surface unless it is soluble. Spores in media which preclude oxygen diffusion are probably more resistant. It is considered that the level of spore inactivation achieved at 2.5 Mrad is very satisfactory, but information and this is expected to occur in 1982. Assessments for several other countries gave similar results. In 1960 and the early pant of 1961, however, when the rate of fallout was low, /sup 90/Sr entered diet mainly from the soil. Variations of / sup 131/I and /sup 90/Sr in the British diet, particularly in milk, are described in detail. Also described is the extensive fallout monitoring scheme in the United Kingdom. A table is provided showing /sup 90/Sr content of various dietary items for
- Research Organization:
- Wantage Research Lab., Berks, Eng.
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-18-017389
- OSTI ID:
- 4059210
- Journal Information:
- Journal of Applied Bacteriology (England), Vol. Vol: 26; Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
Similar Records
RADIOSENSITIVITY OF VARIOUS SPECIES OF BACTERIA UNDER DIFFERENT ENVIRONMENTAL CONDITIONS. Final Report for the Period December 15, 1958 to August 31, 1959
Effect of Radiation Environment on the Thermal Resistance of Irradiated Spores of Clostridium Sporogenes P.A. 3679
Related Subjects
AIR
ALCOHOLS
BACILLUS PUMILUS
BACTERIA
BLOOD SERUM
COBALT 60
DIAGRAMS
EFFICIENCY
EQUATIONS
FILMS
GLASS
HUMIDITY
INSTRUMENTS
LABORATORY EQUIPMENT
LETHAL DOSE
MEDICINE
METHACRYLIC ACID
NUMERICALS
ORGANIC COMPOUNDS
OXYGEN
POLYMERS
POLYVINYLS
QUANTITY RATIO
RADIATION DOSES
RADIATION SOURCES
RADIOSENSITIVITY
SOLUBILITY
SOLUTIONS
SPORES
STERILIZATION
SURFACES
SUSPENSIONS
VARIATIONS