Specific detection of the genus Serpulina, S. hyodysenteriae and S. pilosicoliin porcine intestines by fluorescent rRNA in situ hybridization.

A fluorescent-labelledin situ hybridization method targeting rRNA was devised to facilitate specific identification and diagnosis of diarrhoea and colitis in pigs caused by the genus Serpulina, as well as to distinguish the species Serpulina hyodysenteriae and Serpulina pilosicoli in formalin-fixed colon tissue sections. A genus-specific oligonucleotide probe SER1410 targeting the five species of porcine Serpulina was thus designed. Furthermore, species specific oligonucleotide probes (Hyo1210, Pilosi209 and Pilosi1405) were also designed to detect, identify and differentiate S. hyodysenteriae and S. pilosicoli. These probes clearly demonstrated and possessed the desired specificity, when evaluated by whole cell hybridization on five reference strains and 20 isolates covering the five species of porcine Serpulina. Furthermore, the oligonucleotide probes were specific when used both, for the detection of Serpulina isolates at genus level as well as for specific detection of S. hyodysenteriae and S. pilosicoli in formalin-fixed colon tissue sections from pigs suffering from swine dysentery and porcine colonic spirochaetosis, respectively. Tissue sections were also used from pigs without any intestinal disorders as controls for estimating the specificity of the probes. The probes developed in this study thus had the potential of specific identification and histological recognition obtained in the formalin-fixed tissue samples.