| Abstrakt: |
ABSTRACTPapillomatous digital dermatitis (PDD), an emerging infectious disease of cattle, is characterized by painful, ulcerative foot lesions. The detection of high numbers of invasive spirochetes in PDD lesions suggests an important role for these organisms in the pathogenesis of PDD. PDD-associated spirochetes have phenotypic characteristics consistent with members of the genus Treponema. Partial 16S ribosomal DNA (rDNA) sequence analysis of clonal isolates from California cattle showed that they comprise three phylotypes which cluster closely with human-associated Treponemaspp. of the oral cavity (T. denticolaand T. medium/T. vincentii) or genital area (T. phagedenis). The goal of our study was to apply 16S-23S rDNA intergenic spacer region (ISR) sequence analysis to the molecular typing of U.S. PDD-associated Treponemaisolates. This methodology has potentially greater discriminatory power for differentiation of closely related bacteria than 16S rDNA analysis. We PCR amplified, cloned, and sequenced the ISRs from six California PDD-associated Treponemaisolates and, for comparative purposes, one strain each of T. denticola, T. medium, T. vincentii, and T. phagedenis.Two ISRs that varied in length and composition were present in all the PDD-associated Treponemaisolates and in T. denticola, T. medium, and T. phagedenis. ISR1 contained a tRNAAlagene, while ISR2 contained a tRNAIlegene. Only a single ISR (ISR1) was identified in T. vincentii.Comparative analyses of the ISR1 and ISR2 sequences indicated that the California PDD-associated Treponemaisolates comprised three phylotypes, in agreement with the results of 16S rDNA analysis. PCR amplification of the 16S-tRNAIleregion of ISR2 permitted rapid phylotyping of California and Iowa PDD-associated Treponemaisolates based on product length polymorphisms. |
