Group A streptococcus clones causing repeated epidemics and endemic disease in intravenous drug users

Clones of Group A streptococcus (GAS) may spread epidemically and may be as sociated with enhanced virulence. Sociodemographic and clinical characteris tics, together with bacterial isolates, of 79 patients with GAS infection i n the Berne region between January 1993 and February 1997 were analysed ret rospectively. Using pulsed-field gel electrophoresis, most strains (71%) we re found to belong to one of 12 clones. Clonal strains caused significantly more frequent skin abscesses and more severe invasive disease than non-clo nal strains. The largest clone (M serotype 1) occurred endemically in non-I VDU patients and caused severe disease in most. Three clones occurred almos t exclusively among IVDUs: an M serotype 11 was associated with severe, end emic disease; the other 2 clones, both of M serotype 25, caused epidemics o f needle abscesses. Epidemic and endemic spread of GAS clones among IVDUs m ay be more frequent than previously assumed.