The overarching purposes of this review are to discuss: (1) why spores are so resistant to killing (2) how spores are killed by various agents and (3) various pitfalls that bedevil research on spore killing. Indeed, a large amount of research has been, and continues to be carried out on ways to kill spores and to determine the mechanism of such spore killing. As a consequence of their extreme resistance, spores are difficult to kill, but, thankfully, they can be killed. Given the potential deleterious effects of spores, there has been and still is much interest in methods to kill spores (Cho and Chung 2020 Reineke and Mathys 2020 Setlow 2006, 2013).Ĭoncerns about spores are exacerbated due to their extreme resistance properties, including to UV and γ-radiation, wet and dry heat, desiccation, high pressures, plasma, and a host of chemical agents including acids, bases, alkylating agents and oxidizing agents (Cho and Chung 2020 Reineke and Mathys 2020 Setlow 2006). Finally, spores of one species, Bacillus anthracis, are a potential biological weapon, and was used in this manner in the United States in 2001. Spores of many species are also important vectors for spoilage of a number of types of foods, including juices, bread and dairy products. Accordingly, spores of some species act as vectors for a number of human diseases and intoxications, including severe diarrhea caused by Clostridioides difficile, intoxication caused by Clostridium botulinum or Clostridium perfringens, and food poisoning caused by Bacillus cereus. As a consequence, these species can readily contaminate foods or surfaces with which humans come in contact. Spores of many species of the orders Bacillales and Clostridiales are dormant and extremely resistant to all manner of killing regimens and can survive for long periods in the environment and on a variety of surfaces (Leggett et al. This review will summarize research on spore killing and point out some common flaws which can make results from spore killing research questionable. Factors important to consider in choosing methods for spore killing include the: (1) cost (2) killing efficacy and kinetics (3) ability to decontaminate large areas in buildings or outside and (4) compatibility of killing regimens with the: (i) presence of people (ii) food quality (iii) presence of significant amounts of organic matter and (iv) minimal damage to equipment in the decontamination zone. An alternative strategy is to trigger spore germination, as germinated spores are much easier to kill than the highly resistant dormant spores-the so called “germinate to eradicate” strategy. Many agents are used for spore killing, including moist heat in an autoclave, dry heat at elevated temperatures, UV radiation at 254 and more recently 222 and 400 nm, ionizing radiation of various types, high hydrostatic pressures and a host of chemical decontaminants. Spores of many species of the orders Bacillales and Clostridiales can be vectors for food spoilage, human diseases and intoxications, and biological warfare.

Spore activation key 2017 for ea