Molecular epidemiology of group A streptococcus M type 1 infections.

Data were reviewed about 665 streptococcus M type 1 isolates received by the Streptococcus Reference Laboratory of the New Zealand Communicable Disease Centre between 1980 and 1991. Isolates were voluntarily submitted by diagnostic laboratories throughout New Zealand as part of a surveillance system for streptococcal infections. Over the study period, distribution of M type 1 was uneven, and two waves of infections occurred, each with a distinctive disease pattern. Molecular typing using restriction fragment length polymorphism (RFLP) analysis was used to examine phylogenetic relationships among isolates randomly selected from different geographic locations for each of the years studied. Although six distinct RFLP patterns occurred, most isolates (74%), including those of both waves, belonged to type 1a. This type and one other were also identified among additional isolates originating from Australia and the United States. Typed isolates from cases of severe invasive disease occurring both in the United States and in New Zealand in the late 1980s belonged to RFLP type 1a.