DIFFERENTIATION OF LEPTOSPIRA-INTERROGANS ISOLATES BY IS1500 HYBRIDIZATION AND PCR ASSAYS

Genetic variability among Leptospira interrogans (sensu stricto) serov ars was assessed by Southern blot hybridization and PCR analyses. The experiments used probes directed to sequences in a recently described insertion element, IS1500. Hybridization analysis showed that IS1500 w as present on polymorphic fragments and that differences in these patt erns could be used to identify serovars. Hybridization analysis was al so useful in discriminating between serovar pomona type kennewicki iso lates, making possible the identification of 15 previously unrecognize d genetic groups. A PCR assay was developed in which the primers are p ositioned near the terminal inverted repeats of the element and direct ed outward. This assay yielded characteristic amplification patterns f rom isolates, allowing them to be identified. We applied these assays to several new animal isolates of L. interrogans from Nicaragna, which recently had an outbreak of human leptospirosis. Three groups of isol ates were identified: one strain of serovar pomona type kennewicki and two genetically distinct groups of isolates which may be genetic inte rmediates between serovars canicola and portlandvere. The IS-based typ ing assays described should be useful for epidemiological analysis of leptospirosis.