Essentials of Microbiology for Dental Students

634 Pages·2015·26.81 MB·English

Authors: Bagg, Jeremy; MacFarlane, T. Wallace; Poxton, Ian R.;
Smith, Andrew J.; Bagg, Simon
Title: Essentials of Microbiology for Dental Students, 2nd
Edition
Copyright Š2006 Oxford University Press (Copyright 2006 by Jeremy
Bagg, T. Wallace MacFarlane, Ian R. Poxton, Andrew J. Smith and
Simon Bagg)
> Front of Book > Authors
Authors
Jeremy Bagg
Professor of Clinical Microbiology
University of Glasgow Dental School, Glasgow, UK
T. Wallace MacFarlane
Emeritus Professor of Oral Microbiology
University of Glasgow Dental School, Glasgow, UK
Ian R. Poxton
Professor of Microbial Infection and Immunity
University of Edinburgh Medical School, Edinburgh, UK
Andrew J. Smith
Senior Lecturer in Oral Microbiology
University of Glasgow Dental School, Glasgow, UK
Simon Bagg
Illustrated by
Authors: Bagg, Jeremy; MacFarlane, T. Wallace; Poxton, Ian R.;
Smith, Andrew J.; Bagg, Simon
Title: Essentials of Microbiology for Dental Students, 2nd
Edition
Copyright Š2006 Oxford University Press (Copyright 2006 by Jeremy
Bagg, T. Wallace MacFarlane, Ian R. Poxton, Andrew J. Smith and
Simon Bagg)
> Front of Book > Disclaimer
Disclaimer
Oxford University Press makes no representation, express or implied,
that the drug dosages in this book are correct. Readers must therefore
always check the product information and clinical procedures with the
most up to date published product information and data sheets provided
by the manufacturers and the most recent codes of conduct and safety
regulations. The authors and the publishers do not accept responsibility
or legal liability for any errors in the text or for the misuse or
misapplication of material in this work.
Authors: Bagg, Jeremy; MacFarlane, T. Wallace; Poxton, Ian R.;
Smith, Andrew J.; Bagg, Simon
Title: Essentials of Microbiology for Dental Students, 2nd
Edition
Copyright Š2006 Oxford University Press (Copyright 2006 by Jeremy
Bagg, T. Wallace MacFarlane, Ian R. Poxton, Andrew J. Smith and
Simon Bagg)
> Front of Book > Preface
Preface
The main purpose of this textbook remains unchanged from the first
edition. It sets out to present the science of microbiology in a clinical
context that is relevant to the safe and effective practice of dental
surgery. Many dental school curricula are now changing in line with the
recommendations of the document produced by the UK General Dental
Council, entitled The First Five Years. The two key elements of the
recommendations are that clinical teaching should be brought forward,
ideally starting in Year 1 and that the underpinning basic science,
including microbiology, should be more closely integrated with the
clinical teaching and spread throughout the five years of the course.
When the first edition of Essentials of Microbiology for Dental Students
was prepared, one of our main aims was to produce a book that placed
microbiology firmly in the context of clinical dentistry, an ideal formula
for use in the new style curricula. For this reason, the second edition
has retained the successful format of the first edition, covering the
relevant subject matter in three sections, namely the fundamental
principles of microbiology and immunology, infectious diseases relevant
to dentistry and, finally, oral microbiology. There is extensive cross-
referencing throughout and the book is lavishly illustrated in full colour.
Microbiology is a very rapidly moving discipline. Since the first edition,
a number of infectious diseases such as Creutzfeldt-Jakob Disease and
SARS have emerged as significant clinical problems. There have also
been changes in the epidemiology of certain infections, for example
sexually transmitted diseases. These issues are all covered in this
second edition. The text and lists of further reading have been updated
throughout and changes to antimicrobial drug prescribing regimens
have been included. Major new chapters include those on fungi, human
herpes viruses, infections of the central nervous system, and use of
antimicrobial agents in dentistry. The chapters dealing with
sterilization, disinfection and infection control procedures in dentistry
have been completely re-written, to reflect significant recent changes
in decontamination protocols which have been stimulated by the
problem of prion diseases. In addition to providing a source of further
reading to supplement traditional teaching, the integrated clinical
approach will ensure that the text is valuable to those preparing for
problem-based learning sessions.
Another new feature of the second edition is the inclusion of a
comprehensive glossary of medical, dental and biological terms, all of
which are used in the text itself. It is the authors' experience that
many dental students find the terminology a major problem when they
commence their studies of microbiology. The very clinical emphasis of
the book has dictated that the glossary contains many terms that will
be relevant to other disciplines.
Qualified dentists, particularly those preparing for postgraduate clinical
dental examinations, will also find the book of value. Microbiology is of
immense importance to dentists and it is our hope that the book will
help to make this fascinating subject accessible and relevant to those in
clinical practice.
In summary, we have designed this book to serve as a core reference
text for use throughout all years of the undergraduate dental
curriculum, as a refresher course for postgraduate students and as a
continuing source of reference for dentists in clinical practice. We trust
that our efforts are sufficient to allow these very different groups of
readers to obtain the information they require in a convenient, clear
and interesting way.
J B
T W MacF
I R P
A J S
Glasgow, Edinburgh, 2004
Authors: Bagg, Jeremy; MacFarlane, T. Wallace; Poxton, Ian R.;
Smith, Andrew J.; Bagg, Simon
Title: Essentials of Microbiology for Dental Students, 2nd
Edition
Copyright Š2006 Oxford University Press (Copyright 2006 by Jeremy
Bagg, T. Wallace MacFarlane, Ian R. Poxton, Andrew J. Smith and
Simon Bagg)
> Front of Book > Acknowledgements
Acknowledgements
Microbiology is a rapidly moving field and preparation of the second
edition of this textbook has proved a significant task, since considerable
efforts have been made to bring it fully up to date. The authors would
like to thank all those colleagues and students who have provided
advice on the content of the new edition, in particular Drs Claire
Cameron, Andrew Hall and Jim McMenamin. We also wish to thank all
those who have provided illustrative material and who are
acknowledged in the legends to the relevant figures. Finally, our
grateful thanks are due to the staff of Oxford University Press, in
particular Catherine Barnes and Georgia Pinteau, for their support,
encouragement and willingness to set achievable deadlines.
Authors: Bagg, Jeremy; MacFarlane, T. Wallace; Poxton, Ian R.;
Smith, Andrew J.; Bagg, Simon
Title: Essentials of Microbiology for Dental Students, 2nd
Edition
Copyright ©2006 Oxford University Press (Copyright 2006 by Jeremy
Bagg, T. Wallace MacFarlane, Ian R. Poxton, Andrew J. Smith and
Simon Bagg)
> Table of Contents > Section 1 > 1 - The concept of micro-organisms
1
The concept of micro-organisms
Introduction
The history of microbiology and immunology
Before the development of the light microscope all living organisms
could be divided empirically, without too much debate, into two
kingdoms: the plants and the animals. In the 1660s, Robert Hooke,
using a crude compound microscope, was probably the first person to
see cells; a few years later Antonie van Leeuwenhoek, using the first
high-resolution, single lens microscope, saw microorganisms for the
first time. These microscopic living creatures, some of which were seen
to move, were described as small animals or ‘animalcules’. From
Leeuwenhoek's drawings we know them to be bacteria and protozoa. It
is of interest to note that his specimens included material scraped from
his own teeth.
Fig. 1.1 Some key players in early microbiology and
immunology.
There was a gap of almost two centuries before the development of the
first high-quality compound microscope, together with the pioneering
work of Pasteur, Koch and Lister, established the importance of micro-
organisms as agents of disease, and the science of bacteriology (or the
more modern microbiology) was born (Fig. 1.1). Following the discovery
of penicillin by Fleming, the development of antimicrobial
chemotherapy slowly began, and is now the driving force behind a large
and important branch of microbiology. Much of modern immunology had
its roots in the study of micro-organisms by such key players as
Metchnikoff and Erhlich (Fig. 1.1).
Robert Koch was the first person to prove that micro-organisms caused
disease. Absolute proof can be established by fulfilling the following
postulates, though this raises ethical problems in studies of human
disease.
Koch's postulates
1. The specific micro-organism should be isolated from all cases of a
specific disease, and should not be found in healthy individuals.
2. The specific micro-organism should be isolated from the diseased
individual and grown in pure culture on an artificial medium.
3. The isolated micro-organism should reproduce the specific disease
when inoculated into a healthy individual.
4. The specific micro-organism should be re-isolated in pure culture
from the experimental infection.
Although the original Koch's Postulates remain useful, ‘Koch's Molecular
Postulates’, have been introduced recently. These are covered in
Chapter 4.
Fig. 1.2 The relationships between living
organisms.
Fig. 1.3 Diagram of an idealized prokaryotic
cell.
Early studies on unicellular, microscopic organisms established that
there were several different morphological types. Those resembling
animals were referred to as protozoa and those resembling plants were
termed algae. The yeasts, moulds, and other microscopic forms which
resembled plants but did not possess photosynthetic pigments were the
fungi, while the bacteria tended to be smaller agents, simpler than the
other types, and recognized as causing a range of infectious diseases
(Fig. 1.2). The viruses are a special group of acellular structures which
were discovered much later and which cannot be readily termed living
organisms. Viruses are described in detail in Chapter 6.
Prokaryotic and eukaryotic cells
With the development of the electron microscope in the 1950s it was
for the first time possible to explore the internal architecture of cells. It
soon became apparent that in the whole spectrum of living creatures -
from the simplest bacterium to the most complex higher organism -
there are only two basic types of cell, the prokaryotic cell and the
eukaryotic cell. The prokaryotic cell (Fig. 1.3) is small and simple in
structure without any internal membrane-bound structures or
organelles; while the eukaryotic cell (Fig. 1.4) is larger and more
complex, with an obvious membrane-bound nucleus and other internal
organelles such as mitochondria. Bacteria, together with other similar
micro-organisms classified as rickettsiae, chlamydiae, mycoplasmas,
and cyano-bacteria (formerly blue-green algae), are prokaryotic.
Recently a third cell type has been recognized, which is found in
organisms belonging to the domain Archaea (previously
archaebacteria). These are primitive bacteria-like organisms, often
found in extremes of environment. To date none of the Archaea has
been recognized as a pathogen. All other unicellular and all multi-
cellular organisms are eukaryotic. The fundamental differences in cell
structure (Fig. 1.5) have important consequences when considering
antimicrobial action, as many antimicrobial agents target prokaryotic-
specific structures or metabolic pathways.
On examining the structure of mitochondria (and chloroplasts in plant
cells) it soon becomes apparent that they have many similarities to
prokaryotes: size; 70S ribosomes; undergo binary fission; and have
circular DNA. It is therefore assumed that the eukaryotic cell originally
evolved from a symbiotic relationship between a primitive precursor cell
and intracellular prokaryotic micro-organisms.
Fig. 1.4 Diagram of an idealized eukaryotic
cell.
The diversity of micro-organisms and their
habitats
Micro-organisms were the earliest forms of life on the planet, and many
such primitive types still inhabit the harsh environments which must
resemble those which existed when life first began. Virtually every
ecological niche is colonized by micro-organisms, and each species is
adapted to the specific habitat. The vast majority of micro-organisms do
not cause disease and are saprophytic, obtaining their nutrition from
the breakdown of organic matter. Their primary role is in the various
natural cycles such as the carbon, nitrogen, oxygen, and sulphur cycles
which are concerned with the decomposition of living matter and
recycling of elements vital for the well-being of life on earth.
Atmospheric requirements
Many micro-organisms obtain their energy by fermentation (substrate-
level phosphorylation), a process which does not require oxygen. The
smallest amount of oxygen is toxic to some of these micro-organisms,
or at least inhibits their growth, and these are termed strict anaerobes.
Other micro-organisms perform respiration (oxidative phosphorylation),
and are aerobes. A few species of bacteria can respire anaerobically,