Mainly as a consequence of the development of microbial genetics, genetic analysis has increased enormously its resolving power in recent years, so much so that it now goes beyond that of physical or chemical techniques applied to biological organization (Pontecorvo, 1958).
So far, in genetic analysis the resolving power has been limited only by the refinement of techniques.
In the type of recombination on which classical genetic analysis is based, these structures are the chromosomes and their linearly arranged elements. The latter are recognized as genes as a consequence of their specific activities in metabolism and development (Pontecorvo, 1958).
Complete genome sequences are now available for multiple strains of several bacterial pathogens and comparative analysis of these sequences is providing important insights into the evolution of bacterial virulence. Recently, DNA microarray analysis of many strains of several pathogenic species has contributed to our understanding of bacterial diversity, evolution and pathogenesis (Fitzgerald & Musser, 2001).
Comparative genomics has shown that pathogens such as Escherichia coli, Helicobacter pylori and Staphylococcus aurues contain extensive variation in gene content whereas Mycobacterium tuberculosis nucleotide divergence is very limited. Overall, these approaches are proving to be a powerful means of exploring bacterial diversity, and are providing an important framework for the analysis of the evolution of pathogenesis and the development of novel antimicrobial agents (Fitzgerald & Musser, 2001).
It is of little relevance whether the agents of risk are organic or in ...