Molecular Biotechnology: Principles and Applications - Glick B., Pasternak J. 2002

Molecular Biotechnology of Microbial Systems
Molecular Diagnostics

The success of modern medicine and agriculture often depends on The ability to detect specific Viruses, Bacteria, Fungi, parasitic microorganisms, Proteins, and low-molecular-weight compounds in humans, animals, plants, Water, or soil. For instance, the Prevention and Treatment of any infectious disease are greatly facilitated by the early and accurate identification of the causative pathogen. Many diagnostic Procedures require first culturing the potential pathogen and only then analyzing its physiological properties. Although such tests are highly effective and specific, they are often time-consuming and expensive. This is true for the identification of both bacteria and parasitic microorganisms (Table 9.1). Furthermore, the ability to detect pathogens that grow poorly in culture or cannot be cultured at all is extremely limited. An example is the obligate intracellular parasite Chlamydia trachomatis, which causes chlamydia, a sexually transmitted disease prevalent in North America and Europe. Chlamydia is difficult to diagnose because it requires continuous Cell culture. This often leads to false-negative results (i.e., erroneously diagnosing the absence of the microorganism), resulting in a lack of adequate treatment. Clearly, if culturing is required for detection, only a fraction of all known pathogens can be routinely identified. To overcome this fundamental limitation, molecular diagnostic Methods have been developed, based on immunological approaches or specific DNA detection techniques.

Class="center">Table 9.1. Comparison of selected diagnostic methods for infectious diseases caused by parasitic microorganisms¹⁾

¹⁾ Based on data from Weiss, Clin. Microbiol. Rev. 8: 113—130, 1995.

Any method for detecting pathogens must be sufficiently simple and possess high Specificity and sensitivity. A specific diagnostic test should yield a positive result only for the target microorganism or molecule, while a sensitive test should detect very small amounts of this target, even against a Background of other microorganisms or contaminating molecules in the sample. Simplicity implies that the method is sufficiently productive, efficient, and inexpensive for routine use.

It is estimated that the global market for immunodiagnostic tests was $3.4 billion in 1993 and will grow by 5–10% annually over the next 10–15 years. In 1994, the global market for DNA diagnostic tests was approximately $80 million; it is projected to reach $600 million by 2000 and $2 billion by 2004. In this chapter, we will discuss the principles of several molecular diagnostic methods and their Applications.