GENETIC-VARIABILITY AND MOLECULAR TYPING OF SHIGELLA-SONNEI STRAINS ISOLATED IN CANADA

Restriction fragment length polymorphisms (RFLPs) of genomic DNAs from 49 clinical isolates of Shigella sonnei were analyzed by using a modi fied restriction endonuclease analysis procedure to investigate the ge netic variability of this species. After cleavage with the restriction enzyme Haem or RsaI, DNA samples were electrophoresed in polyacrylami de gels and the RFLP patterns were visualized by silver staining. The results showed that among 20 strains associated with sporadic cases of infection in three Canadian provinces, 15 distinct RFLP patterns were revealed by HaeIII digestion and 12 distinct patterns were revealed b y RsaI digestion. In contrast, the RFLP patterns of individual isolate s within six groups of epidemiologically related isolates were identic al to each other but distinct from those of unrelated isolates, and th ese patterns could be used to determine the genetic relationships betw een isolates associated with separate outbreaks of shigellosis. Our re sults indicate that the modified restriction endonuclease analysis tec hnique represents a rapid, reproducible, and highly discriminatory met hod for the molecular typing of this species.