Inactivation of B. subtilis spores and E. coli endotoxin by ethylene oxide

Exposure of Bacillus subtilis spores to ethylene oxide (EO) showed correlation between the killing rate and the EO concentration, when the temperature was kept at 55 degrees C and the relative humidity at 100%. The co-efficient of dilution was calculated to be 0.9. The effect of EO on Escherichia coli endotoxin was investigated by the chromogenic Limulus Amebocyte Lysate (LAL) test. A solution of endotoxin was dried on glass tubes and exposed to 450 or 900 mg EO/l during 1-46 h under the same conditions as the spore inactivation. The LAL activity of the endotoxin was reduced to about 30%. The EO-treated endotoxin was tested in the rabbit pyrogen test. The summed temperature increase for three rabbits was 0.9 degrees C, while the same assay using untreated test pieces showed an increment of 3.7 degrees C. Administration of the same quantity of EO-treated and untreated endotoxin to the rabbits, as adjusted by the LAL-test, produced the same temperature increment. The addition of polymyxin B (PB) to an endotoxin solution reduced the LAL activity by 75%. Had the endotoxin been exposed to EO, thereby reducing the LAL activity by 70%, addition of PB further reduced the activity by 99%. The reaction of EO on the endotoxin reduced the LAL activity as well as the pyrogenic response and increased the affinity to PB.