ABSTRACT
In the ribotyping technique, chromosomal deoxyribonucleic acid (DNA) is extracted from bacterial cells and cut with a restriction endonuclease enzyme. The fragments are separated by electrophoresis in an agarose gel and transferred to a membrane. Those fragments that are complementary to the probe are highlighted by radioactivity or an enzyme-substrate reaction. Restriction endonucleases are enzymes that bind specifically to and cleave double-stranded DNA within or adjacent to a specific sequence known as the recognition site. The choice of restriction endonuclease for ribotyping of a bacterial species is crucial in respect to the hybridization bands obtained. The purpose of prehybridization is to block the nylon membrane with a foreign DNA so that nonspecific binding of probe DNA to the membrane is reduced to a minimum. Fingerprinting is the most widely used method of comparison in which the hybridization profiles of isolates, preferably on the same membrane, are examined for similarity.
