Identification of porcine serpulina strains in routine diagnostic bacteriology

Serpulina hyodysenteriae, the well known cause of pig dysenteria has to be differentiated in veterinary diagnostic bacteriology from other less virulent or avirulent Serpulina species. S. pilosicoli causes a relatively mild intestinal infection, which has been named Porcine Intestinal Spirochaetosis (PIS). S. intermedin strains have also been described as probable causes of a mild colitis named Porcine Colonic Spirochaetosis (PCS). S. murdochii and S. innocens are probably not pathogenic in pigs. S. pilosicoli appears to have a broad host range, including humans, non-human primates, dogs, guinea pigs, opossums and birds. The close genetic relationship between S. pilosicoli isolated from humans, pigs and dogs raises the possibility that these spirochaetes may be zoonotic. In their institute, the clinical samples received (importantly, transported in special swabs) are inoculated on Tryptycase soy agar (Difco) with 7% sheep blood, 1% yeast extract and an antibiotic mixture. The inoculated plates are incubated in a H-2 and CO2 atmosphere (AnaeroGen, Oxoid) for 3-4 days at 37 degrees C. The first step of the identification is the examination of the strength of the beta-haemolysis and the ring-phenomenon test. Only S. hyodysenteriae gives an enhanced haemolytic pattern around the areas where the agar plugs have been removed (ring-phenomenon +). Additional tests are: indole spot test, alpha-galactosidase, alpha-glucosidase, beta-glucosidase and hippurate tests. Using the above-mentioned diagnostic procedures, 39 S. hyodysenteriae and 4 S. pilosicoli strains have been isolated and identified so far from dysenteria suspected clinical samples in the Veterinary Institute of Debrecen.