Relationship among selected Leptospira interrogans serogroups as determined by nucleic acid hybridization.

Leptospiral DNAs from a variety of Leptospira interrogans serogroups of veterinary significance, as well as a nonpathogenic leptospira, were compared by Southern blot hybridization of EcoRI-digested genomic DNA. The serogroups examined could be assigned to one of three groups on the basis of the degree of cross-hybridization between genomic DNAs. Only a few restriction fragments hybridized between the three groups, and most of these were shown to contain ribosomal DNA. The restriction fragment length polymorphism observed among the intergroup hybridizations allowed differentiation among serogroups and, in some cases, serovars. Under the hybridization conditions used, no hybridization was observed between leptospiral DNA and Leptonema, Escherichia coli, or porcine DNA.