ABSTRACT
The previous chapter summarized many of the now classic technologies and methods being used to identify microorganisms in the laboratory today. Some of these can trace their lineage as far back as the 19th century. They allowed a very simplistic approach to identifying microorganisms, and more specifically those that caused disease. Koch's postulates, espoused in the 1870s, held that diseases were caused by a single species of microorganism, which could be isolated, grown, and then be used to infect an animal and cause the same disease. 1 With the advent of molecular biology in the 1980s and 1990s, newer methods started finding their way into the clinical laboratories and began challenging that concept. The challenge was brought about because technologies used to identify microorganisms changed from those that used phenotypic markers, such as the presence or absence of an enzyme or specific antigen, to those that used genotypic markers, such as the use of specific nucleic acid sequences.
