Evolution of the Clinical Microbiology Laboratory

Over the course of nearly 150 years, the clinical laboratory has diagnosed infectious diseases and identified their causative agents using a variety of approaches. These approaches can be broadly placed into three categories: biochemical, or growth-based methods, molecular and genomic diagnostics, and biomarker and serological detection of blood components. The principle of the biochemical approach is based on isolating an unknown microorganism before conducting a series of growth-based and preformed enzyme detection tests to determine an identification and subsequent antimicrobial susceptibilities. The molecular approach is the newest diagnostic approach utilized by the laboratory and is based on detection of the genetic components of an unknown organism, either isolated or directly in a clinical specimen. There are a variety of molecular techniques, with the polymerase chain reaction serving as the bases of most currently available methods. The detection of infection and inflammatory indicators, as well as serological molecules, have been utilized for diagnostic purposes nearly as long as growth-based identification methods. The biomarker approach to infectious disease diagnosis has primarily occurred outside of the traditional microbiology department, usually within chemistry and hematology where large scale automated instruments provide rapid results. With this focus series we present a concise review, with a brief history, of these different approaches by describing their underlying methodology and advantages and disadvantages, while highlighting specific examples of each, and the internal and external factors which influenced their development.