infectious diseases
Non Nucleic Acid–Based Identification Methods for Infectious Disease
Introduction
Once an organism has been isolated by culture, it must be identified. Identification is important in determining management (eg, drug treatment, isolation measures). Non-nucleic acid–based identification methods use phenotypic (functional or morphologic) characteristics of organisms rather than Nucleic Acid–Based Identification Methods for Infectious Disease . Characteristics of an organism’s growth on culture media, such as colony size, color, and shape, provide clues to species identification and, combined with Gram stain , direct further testing. Numerous biochemical tests are available; each is restricted to organisms of a certain type (eg, aerobic or anaerobic bacteria). Some assess an organism’s ability to use different substrates for growth. Others assess presence or activity of key enzymes (eg, coagulase, catalase). Tests are done sequentially, with previous results determining the next test to be used. The sequences of tests are myriad and differ somewhat among laboratories. Non-nucleic acid–based identification tests may involve Manual methods Automated systems Chromatographic methods Mass spectroscopy Some commercially available kits contain a battery of individual tests that may be done simultaneously using a single inoculum of a microorganism and may be useful for a wider range of organisms. Multiple test systems can be highly accurate but may require several days to yield results. 