Pulsed-Field Gel Electrophoresis: A Tool for Molecular Epidemiology of Bacteria

Pulsed-field gel electrophoresis (PFGE) is the most widely used technique for epidemiological and molecular biology investigations to make long-range physical maps of prokaryotic and eukaryotic genomes. PFGE is a unified typing system for epidemiological investigations of most bacterial pathogens. These methods have been used and adopted for several medically important bacterial species, but have had limited application for veterinary pathogens. Through this technique, we can investigate the geographical comparisons, heterogeneity examination, epidemiology and outbreaks. Accurate epidemiologic investigations require an assessment of relatedness between individuals with similar infections in order to determine if animal to animal spread has occurred. Epidemiologic typing systems are used to study population dynamics and spread of organisms that undergo clonal reproduction (i.e. bacteria). The digestion of total genomic DNA is done with restriction endonucleases. These enzymes cut the chromosome at infrequent intervals, producing relatively large fragments that can then be separated by using PFGE. Typing systems must be assessed according to performance criteria, namely, typeability, reproducibility, stability, discriminatory power, epidemiologic concordance and typing system concordance.