FUNDAMENTALS OF MOLECULAR

Infectious agents have traditionally been detected in clinical samples by microscopic identification, by isolation after culturing or by detection of a specific host immune response31-Microscopy is useful in identifying bacteria, fungi and parasites, but is generally not able to recognize viruses. Although considered the most sensitive diagnostic method, culture cannot be used routinely in all cases, especially in viral diseases. The progress immunology has achieved in recent years has made possible the detection of many micro organisms through immunocytochemistry and by different serologic reactions using ELISA and radioimmunoassay. However, some infections cannot be identified due to low amount or absence of relevant antigens or antibodies. In the last few years molecular biology experienced a tremendous advance and provided powerful tools to diagnose many infectious diseases. Today, Desoxyribose Nucleic Acid (DNA) and Ribose Nucleic Acid (RNA) technology is becoming increasingly used as effective options for the detection of infectious agents. All microbes have their own individuality expressed at the genetic level in their sequences of nucleic acids. The pinpointing of these specific sequences by the procedures described below permits accurate, sensitive and effective diagnosis of a large number of infectious diseases