Inactivation of Geobacillus stearothermophilus spores by alkaline hydrolysis applied to medical waste treatment

Abstract

Although alkaline hydrolysis treatment emerges as an alternative disinfection/sterilization method for medical waste, information on its effects on the inactivation of biological indicators is scarce. The effects of alkaline treatment on the resistance of Geobacillus stearothermophilus spores were investigated and the influence of temperature (80 degrees C, 100 degrees C and 110 degrees C) and NaOH concentration was evaluated. In addition, spore inactivation in the presence of animal tissues and discarded medical components, used as surrogate of medical waste, was also assessed. The effectiveness of the alkaline treatment was carried out by determination of survival curves and D-values. No significant differences were seen in D-values obtained at 80 degrees C and 100 degrees C for NaOH concentrations of 0.5 M and 0.75 M. The D-values obtained at 110 degrees C (2.3-0.5 min) were approximately 3 times lower than those at 100 degrees C (8.8-1.6 min). Independent of the presence of animal tissues and discarded medical components, 6 log10 reduction times varied between 66 and 5 min at 100 degrees C-0.1 M NaOH and 110 degrees C-1 M NaOH, respectively. The alkaline treatment may be used in future as a disinfection or sterilization alternative method for contaminated waste.