Chapter 10 : Spore Resistance Properties

Abstract:

The extreme resistance of spores of members of the Bacillales and Clostridiales orders is probably the property most closely associated with these spores. In the past, this extreme resistance contributed to claims for spontaneous generation and, in more recent years, has contributed to the applied importance of spores in a number of different areas including the following. (i) The food industry. Given that spores of a number of species are ubiquitous in the environment, they routinely contaminate foodstuffs. Since spores of many species are vectors for food spoilage and food-borne disease, the food industry commits significant resources to eliminating spores in order to make foods sterile, in particular to eliminate extremely dangerous spores such as those of Clostridium botulinum ( 1 , 2 ). Indeed, many of the requirements for food sterilization regimens in the United States are designed to completely inactivate C. botulinum spores. (ii) The medical products industry. Just as in the food industry, spores present similar concerns in the medical products industry, including the manufacture of medical devices and parenteral drugs, again because of the involvement of spores in a number of human diseases. (iii) The health care industry. There is an increasing prevalence of disease due to Clostridium difficile in hospital and long-term nursing care facilities, largely because of the resistance of C. difficile spores and thus their persistence in patient care environments unless stringent environmental decontamination regimens are followed. (iv) Vaccine development. There is increasing interest in spores as carriers of proteins important as vaccines ( 3 , 91 ), in large part because of spores’ extreme stability to normal and even extreme environmental conditions. This may allow the delivery of vaccines to areas where cold storage is difficult and is facilitated by utilizing the spore coat as a means to deliver immunogens. (v) Probiotics. Since spores are dormant, as such, they will not be probiotics. However, the administration of spores with their resistance to low pH conditions in the stomach is a route to effectively deliver potentially beneficial bacteria to the lower gastrointestinal tract ( 4 , 91 ). Notably, it is the C. difficile spore’s resistance to stomach acidity that is the reason that the oral route is the major mechanism for C. difficile infection. (vi) Biological warfare. While the disease-causing potential of Bacillus anthracis is one reason that this organism has come to the fore as a biological weapon, in particular of bioterror (S. L. Welkos, unpublished data), the major reason for this organism’s visibility in this area is that B. anthracis spores are so resistant. This makes their dispersal either in water or as an aerosol relatively simple and ensures that these spores will persist in contaminated environments and will thus require stringent decontamination methods for their elimination.