Field inversion gel electrophoresis (FIGE) was performed on 139 isolates of group A streptococcus (GAS) representing 72 different M types. Multiple isolates were tested for 27 M types (range, 2 -19). Each of the M types tested had at least one unique banding pattern that was not observed in any other M type. For 23 of 27 M types for which multiple isolates were available, band profiles of the isolates were the same or differed by õ3 bands and are considered indistinguishable or closely related.

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... These data demonstrate that FIGE of the DNA of GAS identifies differences between and within M types.