Mims’ Medical Microbiology and Immunology 6th Edition

Book Preface

Previous editions of Mims’ Medical Microbiology have adopted the approach that the interaction between infectious disease and host response is best understood as a give-and-take conflict. The sixth edition continues this tradition, revising the title to Mims’ Medical Microbiology and Immunology to better reflect the subject. Continued recognition of Cedric Mims’ founding contribution to this work is seen not only in the title but also in the foreword to this sixth edition. Ivan Roitt, who played a major role in earlier editions, has relinquished his role as a main author and we gratefully acknowledge his contribution. Overall, this edition benefits from significant revision in multiple areas. The introductory chapters continue to present fundamental principles of infectious agents and host defences but now include the newly recognized importance of the human microbiota. Subsequent chapters present an updated overview of the general principles behind the infectious agent – immune response conflict, followed by a chapter-specific consideration of system-oriented conflict scenarios. Final
chapters provide a revised consideration of issues affecting diagnosis and control of the conflict especially centring on newer molecular (especially DNA-sequence-based) approaches. Bibliographic references continue to include current Internet resources. Online access to interactive extras is provided via Elsevier’s STUDENT CONSULT website (www.studentconsult. com) including questions and answers, mostly in USMLE format, the Pathogen Parade (infectious agent) index, and a new Vaccine Parade index. Molecular approaches continue to inform and enlarge our understanding of pathogen–host interaction at a record pace. In this new edition of Mims’ Medical Microbiology and Immunology, we believe the student will find a logical and unified approach to the subject that is readable, exciting, and informative.

Richard V Goering, Hazel M Dockrell,
Mark Zuckerman, Peter L Chiodini 2017

INTRODUCTION

Microbes and parasites The conventional distinction between ‘microbes’ and ‘parasites’ is essentially arbitrary Microbiology is sometimes defined as the biology of microscopic organisms, its subject being the ‘microbes’. Traditionally, clinical microbiology has been concerned with those organisms responsible for the major infectious diseases of humans and whose size makes them invisible to the naked eye. Thus, it is not surprising that the organisms included have reflected those causing diseases that have been (or continue to be) of greatest importance in those countries where the scientific and clinical discipline of microbiology developed, notably Europe and the USA. The term ‘microbes’ has usually been applied in a restricted fashion, primarily to viruses and bacteria. Fungi and protozoan parasites have historically been included as more minor contributors, but in general they have been treated as the subjects of other disciplines (mycology and parasitology). Although there can be no argument that viruses and bacteria are, globally, the most important pathogens, the conventional distinction between these as ‘microbes’ and the other infectious agents (fungi, protozoan, worm and arthropod parasites) is essentially arbitrary, not least because the criterion of microscopic visibility cannot be applied rigidly (Fig. Intro.1). Perhaps we should remember that the first ‘microbe’ to be associated with a specific clinical condition was a parasitic worm – the nematode Trichinella spiralis – whose larval stages are just visible to the naked eye (though microscopy is needed for certain identification). T. spiralis was first identified in 1835 and causally related to the disease trichinellosis in the 1860s. Viruses and bacteria comprise just over half of all human pathogen species (Table Intro.1). THE CONTEXT FOR CONTEMPORARY MEDICAL MICROBIOLOGY Many microbiology texts deal with infectious organisms as agents of disease in isolation, both from other infectious organisms and from the biological context in which they live and cause disease. It is certainly convenient to consider organisms group by group, to summarize the diseases they cause, and to review the forms of available control, but this approach produces a static picture of what is a dynamic relationship between the organism and its host. Host response is the outcome of the complex interplay between host and parasite. Host response can be discussed in terms of pathological signs and symptoms and in terms of immune control, but it is better treated as the outcome of the complex interplay between two organisms – host and parasite; without this dimension a distorted view of infectious disease
results. It simply is not true that ‘microbe + host = disease’, and clinicians are well aware of this. Understanding why it is that most host–microbe contacts do not result in disease, and what changes so that disease does arise, is as important as the identification of infectious organisms and a knowledge of the ways in which they can be controlled. We therefore continue to believe that our approach to microbiology, both in terms of the organisms that might usefully be considered within a textbook and also in terms of the contexts in which they and the diseases they cause are discussed, provides a more informative and more interesting picture of these dynamic interrelationships. There are many reasons for having reached this conclusion, the most important being the following: • A comprehensive understanding now exists at the molecular level of the biology of infectious agents and of the host–parasite interactions that lead to infection and disease. It is important for students to be aware of this understanding so that they can grasp the connections between infection and disease within both individuals and communities and to be able to use this knowledge in novel and changing clinical situations. • It is now realized that the host’s response to infection is a coordinated and subtle interplay involving the mechanisms of both innate and acquired resistance, and that these mechanisms are expressed regardless of the nature and identity of the pathogen involved. Our present understanding of the ways in which these mechanisms are stimulated and the ways in which they act is very sophisticated. We can now see that infection is a conflict between two organisms, with the outcome (resistance or disease) being critically dependent upon molecular interactions. Again, it is essential to understand the basis of this host–pathogen interplay if the processes of disease and disease control are to be interpreted correctly.