Nucleotide Sequencing and Analysis of 16S rDNA and 16S-23S rDNA Internal Spacer Region (ISR) of Taylorella equigenitalis, as an Important Pathogen for Contagious Equine Metritis (CEM)

The primer set for 16S rDNA amplified an amplicon of about 1500 bp in length for three strains of Taylorella equigenitalis (NCTC11184T, Kentucky188 and EQ59). Sequence differences of the 16S rDNA among the six sequences, including three reference sequences, occurred at only a few nucleotide positions and thus, an extremely high sequence similarity of the 16S rDNA was first demonstrated among the six sequences. In addition, the primer set for 16S-23S rDNA internal spacer region (ISR) amplified two amplicons about 1300 bp and 1200 bp in length for the three strains. The ISRs were estimated to be about 920 bp in length for large ISR-A and about 830 bp for small ISR-B. Sequence alignment of the ISR-A and ISR-B demonstrated about 10 base differences between NCTC11184T and EQ59 and between Kentucky188 and EQ59. However, only minor sequence differences were demonstrated between the ISR-A and ISR-B from NCTC11184T and Kentucky188, respectively. A typical order of the intercistronic tRNAs with the 29 nucleotide spacer of 5'-16S rDNA-tRNAIle-tRNAAla-23S rDNA-3' was demonstrated in the all ISRs. The ISRs may be useful for the discrimination amongst isolates of T. equigenitalis if sequencing is employed.