Survival of Brachyspira hyodysenteriae and B. pilosicoli in terrestrial microcosms.

The survival of Brachyspira hyodysenteriae and Brachyspira pilosicoli was investigated at 10 degrees C in laboratory microcosms consisting of soil, porcine faeces, and in soil mixed with 10% porcine faeces, respectively. By plate spreading, survival of B. hyodysenteriae was found to be 10, 78 and 112 days in soil, soil mixed with 10% faeces, and in porcine faeces, respectively. The identities of the colonies on the plates were confirmed using PCR targeting 23S rDNA for specific detection of B. hyodysenteriae. A positive PCR signal could be obtained up to 112 days in all microcosms by direct extraction of DNA from microcosms followed by PCR. The survival time for B. pilosicoli was 119 days in pure soil and 210 days in soil mixed with 10% porcine faeces and in pure faeces, respectively, as determined by plate spreading followed by PCR. On the other hand, by direct extraction of DNA followed by specific detection by PCR. B. pilosicoli could be detected up to 330 days in all microcosms.Dot blot hybridisation with digoxigenin-labelled specific oligonucleotide probe targeting rDNA could not be used for direct detection of Brachyspira spp. from microcosms due to low sensitivity. However, it was used for confirmation of the identity of colonies and proved to be a useful technique. These results show that the two Brachyspira species may survive in outdoor environment for the times shown in these investigations using laboratory microcosms.