Chapter 12.4 : Molecular Methods for Epidemiologic Typing of Microorganisms

Abstract:

The ability to identify specific strains within a species of pathogen is an important aid in the rational development of effective measures to prevent and control nosocomial infections. The efforts of both microbiologists and hospital epidemiologists are facilitated greatly by the availability of the newer molecular epidemiologic typing techniques. The variety of molecular epidemiologic tools available at present is considerable, and based on current experience the methods that appear to be the most practical and useful for both large- and small-scale epidemiologic studies are the DNA-based methods such as pulsed-field gel electrophoresis (Table 12.1-5). Although these methods clearly have limitations, they generally are a significant improvement over the more conventional typing methods, many of which are too cumbersome, insensitive, and time-consuming to be of practical value for epidemiologic evaluations. It is important to understand that no single technique is universally applicable and that the choice for a particular application is related to the species studied, the scope of the question posed, and the convenience of the technique. The techniques of molecular epidemiology are useful in answering real clinical and infection control questions and are not limited to research uses. Examples include distinguishing between relapse and reinfection in an individual patient and in tracking the spread of an individual strain of a bacterium or fungus within the hospital environment ( 1 – 3 ).