Genotypic approaches to the diagnosis of bacterial infections: plasmid analyses and gene probes.

Practical genetic approaches have been helpful in the diagnosis, epidemiology, and taxonomy of bacterial pathogens encountered in our laboratory at the Centers for Disease Control. There are many examples in which plasmid profiles have been used to define epidemic strains of enteric bacteria, staphylococci, pseudomonads, vibrios, and other pathogenic bacteria. Current methodologies should allow the microbiology laboratory to use plasmid profiles routinely and to identify plasmids associated with bacterial pathogenesis. Simplified DNA-DNA hybridization procedures have been used in our laboratory to survey or "probe' thousands of Escherichia coli colonies for the presence of enterotoxin genes, eliminating traditional tissue culture or animal assays. Research scientists continue to develop gene probes for a number of bacterial toxins and hemolysins and for the identification of pathogens such as legionellae and salmonellae. These and other probes as well as hybridization "kits' may be commercially available to diagnostic laboratories within the next few years.