[Evaluation of the use of bioindicators of spore-containing soil for the evaluation of steam sterilization in general practice conditions].

In this publication quantitative researches on the use of so-called spore-containing earth for monitoring steam-sterilization are described. The three factors necessary for medical steam-sterilization - the correct combination of saturated steam, temperature and time - cannot kill all the spores in their original earth. The surviving of single spores in native earth after steam-sterilization is of use to the calculation of the resistance of spore-containing earth by saturated steam at 121 degrees C (250 degrees F). Besides the resistance depends on the conditions under which the earth was tested for surviving germs. The relative frequency of sterile samples after steam-penetration (Po) was utilized for the calculations of characteristic lines according to the transformation in y = lg ( - ln Po) The quantity of the germs killed (G) was exactly computed by the integration of steam-temperature and the time of penetration according to the equation G = fk X dt The quantities of k were calculated and they are discovered in Table 1. A charge of spore-containing earth only then will be suitable for monitoring steam-sterilization if its characteristic line fulfils the requirements of DIN 58946, part 4, October 1978. The evaluations demonstrate that it is necessary to adapt the samples of spore-containing earth to specific conditions of incubation. The tests carried out show that native earth as bioindicator is well suited for monitoring steam-sterilization by a bacteriological laboratory (Fig. 1).(ABSTRACT TRUNCATED AT 250 WORDS)