LEPTOSPIRA FAINEI SP, NOV., ISOLATED FROM PIGS IN AUSTRALIA

Pathogenic leptospires can be causative agents of reproductive problem s in pigs. Cultures of uteri and kidneys from two pig herds in New Sou th Wares and Victoria (Australia) yielded five strains identified as L eptospira on morphological and cultural grounds. Phenotypic characteri stics (growth at 13 and 30 degrees C, growth in the presence of 8-azag uanine) were intermediate between those of pathogenic and saprophytic leptospires. No cross-agglutination was observed with reference antise ra representing the 24 pathogenic serogroups and the main saprophytic ones. Antiserum against one of the strains did not agglutinate referen ce strains representative of any serogroup. This provided evidence of a new serovar, designated hurstbridge. Genomic characterization of the five strains was achieved using five molecular approaches. Mapped res triction site polymorphisms in the rrs (16S rRNA) gene were not relate d to those of any reference strains. Arbitrarily primed PCR fingerprin ts suggested clonality of the five strains. The strains all showed an identical and unique PFGE profile. PCR, using primers specific for the rrs gene of pathogenic leptospires, amplified corresponding sequences from the strains, DNA-DNA hybridization (and reciprocal experiments) using the S1 nuclease/TCA method was performed between one of the stra ins and the reference strains of Leptospira species. The homology rang ed from 0 to 36% (the latter being with Leptospira inadai) thus satisf ying the criterion of a new species, Leptospira fainei (type strain BU T 6(T)). Phylogenetic analysis of 16S rRNA sequences showed that L. fa inei and L. inadai formed a clade separate from the previously recogni zed 'saprophyte' and 'pathogen' clades.