The detection of genetic variation in Leptospira interrogans serogroup ICTEROHAEMORRHAGIAE by ribosomal RNA gene restriction fragment patterns.

Deoxyribonucleic acid from Leptospira interrogans serogroup ICTEROHAEMORRHAGIAE reference strains together with clinical and animal isolates were cleaved with EcoRI, electrophoresed and transferred to nylon membranes. An Escherichia coli MRE 600, 16S + 23S ribosomal RNA template was used in the synthesis of a single strand biotin-labelled cDNA probe using a reverse transcriptase. Ribosomal RNA cistrons present in the DNA fragments of strains were located using the cDNA probe. Between 4 and 7 well defined ribosomal RNA restriction bands were detected for the leptospires studied that varied in size from 12.1 to 0.57 kb. The hybridisation patterns were distinctive and unique for the reference strains that allowed for their characterisation. Similar patterns were observed for I. budapest M 20, I. "icterohaemorrhagiae" Ictero I and the type strain, I. icterohaemorrhagiae RGA. Clinical isolates and a isolate from a rat were compared with reference strain DNA patterns and identified as being similar to I. copenhageni M 20, I. "icterohaemorrhagiae" Ictero I and I. icterohaemorrhagiae RGA. These results indicate that ribosomal DNA fingerprinting may be useful in the classification and molecular epidemiology of pathogenic leptospires.