The importance of the molecular approach to medical
microbiology goes far further than merely providing
information about mechanisms of pathogenicity. The central
objective of medical science is the prevention of disease.
The first great preventive insights, based on
epidemiological observations, were the recognition by the
social pioneers of the 19th century of the importance of
clean drinking water and the safe disposal of sewage. Of
almost equal importance was the discovery of toxoids at
the end of the 19th century. This, together with later
developments in immunology and the manipulation of
genes and immunogens, has given rise to highly successful
vaccines. A striking example is the vaccine against
Haemophilus influenzae type b, which promises to eliminate
the risk of childhood meningitis due to this virulent
pathogen [7,8]. As will be apparent from the chapters that
follow, molecular biology is yielding far-reaching insights
into every branch of medical microbiology.