In the past much of the practice and thinking in medical
and particularly in clinical bacteriology was based on the
classical views of bacteria and their behaviour. These
views have changed rapidly under the influence of accumulating
fundamental molecular knowledge. These
changes, already evident in the better understanding of
bacterial pathogenicity and pathogenesis, are extending
into every branch of medical and clinical microbiology,
from bacterial morphology at one extreme to ecology,
epidemiology and prevention at the other. At the same
time molecular techniques are finding an increasing use
in the diagnostic laboratory. In addition, the molecular
approach has far-reaching implications for the understanding
of the interaction between host and microbe [31,32].