Clonal differences within M-types of the group A streptococcus revealed by pulsed field gel electrophoresis

Digestion of chromosomal DNA with the rare cutting restriction enzyme Sfi I in association with pulsed field gel electrophoresis was used to observe restriction fragment length polymorphisms (RFLP) among isolates of group A Streptococcus. Streptococci examined included isolates belonging to the same M-type (epidemiologically related and unrelated), and isolates from other M-types. RFLP patterns were quite distinct between all serotypes tested. More importantly, isolates from within a serotype could be differentiated by this technique.