Antisepsis, Disinfection, and Sterilization. Gerald E. McDonnell
ABOUT THE AUTHOR
Gerald E. McDonnell received a B.Sc. degree in medical laboratory sciences from the University of Ulster (1989) and a Ph.D. in microbial genetics at the Department of Genetics, Trinity College, University of Dublin (1992). His graduate work involved studies on the control of gene expression in Bacillus subtilis. He spent 3 years at the Mycobacterial Research Laboratories, Colorado State University, investigating the mechanisms of antibiotic resistance and cell wall biosynthesis in mycobacteria. In 1995 he joined the St. Louis, Mo., operations of ConvaTec, a division of Bristol-Myers Squibb, as a group leader in microbiology in the research and development of skin care, hard surface disinfection, and cleaning chemistries. He then joined STERIS Corporation and has worked for STERIS for more than 10 years in the United States and in the company’s European, Middle East, and Africa (EMEA) region on the development, research, and support of infection and contamination prevention products and services, including cleaning, antisepsis, disinfection, and sterilization. Dr. McDonnell is currently the vice president of research and EMEA affairs for STERIS, based at its facility in Basingstoke, United Kingdom. He is responsible for the development and support of decontamination processes and services, and he provides training on various aspects of decontamination and contamination control. His basic research interests include infection prevention, decontamination microbiology, emerging pathogens, and modes of action and resistance to biocides. His work also includes the development and implementation of international and national guidance and standards in decontamination. He has published widely in peer-reviewed journals and books, has been granted patents in decontamination technologies, and frequently gives presentations on various aspects of his work at scientific meetings around the world.
IMPORTANT NOTICE
The author has taken great care to confirm the accuracy of the information presented in this book, based on peer-reviewed publications at the time of preparation. However, the author and publisher make no warranty, expressed or implied, that the information in this book is accurate or appropriate for any particular facility, environment, or individual situation, and they are not responsible for any consequences of application of any of the information in this book by any reader. The inclusion of specific products, instruments, reagents, or methods does not represent any endorsement by the American Society for Microbiology, ASM Press, or the author. Nor does the inclusion or inadvertent exclusion of any product, instrument, reagent, or method reflect a preference for any product over other similar competitive products. The comments included in this book are strictly those of the author and do not necessarily reflect the views of his employer. Some of the products, tests, methods, and applications discussed in this book have particular U.S. Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) approval for selective uses; further specific approvals or exclusions may also apply to other international regulatory agencies within specific geographic areas or countries. It is the responsibility of the reader to ensure the necessary local approval status of any product or process that is considered for use in his or her particular hospital, industrial, environmental, or private setting or practice.
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INTRODUCTION
1.1 GENERAL INTRODUCTION
Microbiology is the study of microscopic organisms (microorganisms). Microorganisms play important roles in our lives, for our benefit as well as to our detriment. Of primary interest are those microorganisms that cause diseases under a variety of circumstances. Other issues include the economic aspects associated with microbial contamination, such as food spoilage, plant infections, and surface damage. The control of microorganisms is therefore an important concern in preventing contamination, as well as removing or reducing it when it occurs. A variety of physical and chemical methods are used for these purposes in antisepsis, disinfection, and sterilization applications. Disinfection and sterilization are used for the control of microorganisms on surfaces, in liquids, or in areas, while antisepsis is particularly associated with microbial reduction on the skin or mucous membranes. These biocidal applications are varied and include skin washing, wound treatment, product preservation, food and water disinfection, surgical-device decontamination, and product sterilization. Many of these processes have been used historically and are described in many ancient texts and writings. Despite this, it is only in the last 150 years, as our knowledge and understanding of microbiology has expanded, that the impact of antiseptics, disinfectants, and sterilants has been truly appreciated. Their utilization has played and continues to play an important role in significantly reducing the incidence of infectious diseases, such as gastroenteritis and pneumonia. Today, microorganisms are still a significant cause of morbidity, mortality, and economic loss, and we continue to be challenged with the identification of “newer” microorganisms, like Legionella, antibiotic-resistant bacteria, human immunodeficiency virus (HIV), Ebola virus, viroids, and prions.
Biocidal processes include many physical and chemical methods. Physical processes include heat (e.g., steam) and radiation (e.g., UV radiation). A wide range of chemicals, such as aldehydes, halogens, and phenolics, are also used due to their antimicrobial activities. The choice and use of a biocide will depend on the required application. For example, many aggressive chemicals or high-temperature processes can be used on various hard surfaces, like medical devices, but would not be acceptable for use as antiseptics on the skin. Therefore, there are three primary considerations in the choice of a biocide: antimicrobial efficacy, safety, and compatibility. There is no perfect biocide for any application, but the desired attributes include the following:
Activity against a wide range of (if not all) microorganisms
Rapid activity
Efficacy in the presence of contaminating organic and inorganic materials, which can inhibit the activity of the biocide
Low or no toxicity, irritancy, mutagenicity (causing genetic mutations), or carcinogenicity (causing cancer)
Safe use
Lack of damage to surfaces or areas (compatibility)
Lack of unwanted or toxic residues
Stability, yet ability to be readily broken down in the environment
Environmental friendliness
It is clear that the advantages and disadvantages of each biocide should be considered in deciding its suitability in a given application.
This book describes the major antiseptic, disinfectant, and sterilization practices that are used. For the purpose of introduction, this chapter gives a brief description of the various types of target microorganisms, as well as a discussion of some key considerations for biocidal applications, including the evaluation of efficacy, formulation effects, and the importance of cleaning. Chapters 2 and 3 describe the various types of physical and chemical biocides and biocidal processes, including filtration, which is not a true biocidal process but is widely used in the disinfection and sterilization of liquids and gases. For each biocide group, the various types, applications, spectra of antimicrobial activities, advantages, and disadvantages and a brief discussion of the mode of action are given. Chapter 4 addresses the use of biocides as antiseptics and antiseptic applications. Chapters 5 and 6 discuss various types of physical and chemical sterilization methods, which are considered distinct from disinfection applications. Chapter 7