Chapter 1 Introduction
Microbiology (Greek: mīkros small; bios life), so called because it primarily deals with organisms too small for the naked eye to see, encompasses the study of organisms that cause disease, the host response to infection and ways in which such infection may be prevented. For our purposes the subject can be broadly classified into general, medical and oral microbiology.
Dental students need both a basic understanding of general and medical microbiology, and a detailed knowledge of clinical oral microbiology in order to diagnose oral microbial infections, which are intimately related to the overall treatment plan for their patients. Moreover, the two major oral disorders – caries and periodontal disease – that the dental practitioner is frequently called upon to treat are due to changes in the oral bacterial ecosystem, and a grasp of these disease processes is essential for their appropriate management.
The impact of these infections on the health and welfare of the community is simply astonishing. It has been estimated, for instance, that caries and periodontal disease are the most costly diseases that the majority of the population has to contend with during their lifetime, and the number of working hours lost due to these infections and the related cost of dental treatment worldwide amount to billions of dollars per annum (e.g. more than 81 billion dollars in the USA in 2006). This is not surprising as it is generally accepted that periodontal disease is the most common affliction of the human kind.
The advent of the human immunodeficiency virus (HIV) infection in the early 1980s and the subsequent concerns on cross infection via contaminated blood and instruments have resulted in an increased regimentation of infection control practices in dentistry. Furthermore, many patients are acutely concerned about possible infection transmission in clinical settings because of the intense, and sometimes unwarranted, publicity given to these matters by the media. The dental practitioner should therefore be conversant with all aspects of infection control in the clinical environment, not only to implement infection control measures but also to advise the dental team (dental surgery assistants, dental hygienists and other ancillary personnel) and to allay patients’ unfounded fears. For all these and many other reasons, which the student will discover in the text, the discipline of microbiology is intimately woven into the fabric of dentistry and comprises a crucial component of the dental curriculum.
It should also be realized that new microbial diseases emerge incessantly (due to reasons given below), and the book you are now holding is a primer for understanding and managing such future scenarios, especially in the context of infection control.
Infectious agents have been adversaries of humans for millennia. It has been postulated that diseases such as plague have wiped out civilizations in ancient times while humans in turn have won the battle against microbes in more recent times (e.g. eradication of smallpox). Such new diseases are given the terms emerging infections or re-emerging infections (Fig. 1.1), and they are broadly categorized as:
Fig. 1.1 Global prevalence of some emerging and re-emerging diseases. S. aureus, Staphylococcus aureus; E. coli, Escherichia coli; vCJD, variant Creutzfeldt–Jakob disease; SARS, severe acute respiratory syndrome; HIV, human immunodeficiency virus.