VIR TYPING - A LONG-PCR TYPING METHOD FOR GROUP-A STREPTOCOCCI

We have developed a new procedure (Vir typing) for typing Streptococcu s pyogenes, by amplifying the entire 5- to 7-kb variable vir regulon b y long PCR. The amplified DNA Is then cleaved with HaeIII and visualiz ed by ethidium bromide fluorescence after agarose gel electrophoresis. A simple procedure for preparing DNA of sufficiently high quality fro m 96 samples was employed simultaneously. This DNA was also used to de velop a random amplified polymorphic DNA (RAPD) procedure. The discrim inatory power of the two DNA-based procedures was compared with previo us methods, id typing, and multilocus enzyme electrophoresis. Both pro cedures were highly discriminatory, but the stoichiometric yield of re striction fragments in Vir typing allows unambiguous interpretation of results.