Detection of DNA restriction fragment polymorphisms in Streptococcus equi

Large-restriction-fragment (LRF) polymorphisms in Streptococcus equi (S equ i subspecies equi) were studied by pulsed-field gel electrophoresis. Five o r six chromosomal fragments of between 194 and 915 kb were separated by dig estion with the restriction endonuclease Notl. All 20 isolates of S equi, i ncluding 12 from independent Japanese outbreaks, four from independent Amer ican outbreaks, two from a single Irish outbreak, us vaccine strain F43, an d type strain NCTC 9682 were successfully typed. Seven distinctive, reprodu cible and stable types were identified. The 12 Japanese isolates collected between 1992 and 1998 were of LRF type II suggesting that they were derived from the same source. The remaining eight isolates were of six types. The results indicate that LRF typing should be a useful technique for investiga ting the source and transmission of S equi.