Application of Random Amplified Polymorphic DNA (RAPD) and Pulsed-Field Gel Electrophoresis (PFGE) Analysis to Listeria monocytogenes: A Review of Methodology and Results

Random amplified polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE) analyses have been found to be powerful molecular methods for differentiating isolates of a given bacterial species. When applied to Listeria monocytogenes, both methods have been found highly effective in tracking isolates involved in food borne outbreaks of listeriosis and in identifying routes of contamination in food processing plants. Among the two methods, PFGE is considered somewhat superior in discriminatory power. However, the use of two or more independent random primers with RAPD is considered to result in a level of discrimination equal to that of PFGE. When results from both methods are combined, a maximum level of discrimination that exceeds that obtained with both methods independently can be achieved. Individually, both methods far exceed the discriminatory power of serotyping and phage typing of L. monocytogenes strains in that serotypes 1/2a, 1/2b, and 4b, represent over 90% of all human isolates, and phage typing at times has allowed typing of no more than about 50% of isolates. In addition, both RAPD and PFGE on occasion have been found to be superior to ribotyping, multilocus enzyme electrophoresis, and restriction enzyme analysis of L. monocytogenes isolates.