Diagnosis of swine dysentery and spirochaetal diarrhoea. Part I: Cultural and biochemical differentiation of intestinal serpulina in laboratory diagnosis

Frequent incidence of Serpulina strains showing all cultural and biochemica l characteristics of Serpulina (S.) hyodysenteriae except of being indole n egative, and a-galactosidase positive isolates showing strong haemolysis on Columbia agar with 5 % sheep blood and trypticase soy agar with 5 % ox blo od, respectively, was the cause to evaluate common biochemical and cultural methods in Serpulina routine diagnostics. To this purpose ten type and ref erence strains as well as 47 field strains were examined for their ability to produce indole, haemolysis, hippurate cleavage, alpha-galactosidase, alp ha-and beta-glucosidase activity. Two four-hour identification-systems were used, RapID ANA II and Rosco diagnostic tablets. The ability to produce in dole was determined by different methods. All investigations were carried o ut at least two times. For the investigation of haemolytic patterns tryptic ase soy agar with 10 % ox blood proved to be most effective. Results receiv ed using this agar could always be confirmed by the ring phenomenon. Determ ining the ability to produce indole by adding p-dimethylaminocinnamaldehyde to bacterial growth collected on a cotton swab was confirmed to be more se nsitive than other methods. Both four-hour-systems were shown to be useful in Serpulina diagnostics, though in the RapID ANA II only four of 18 availa ble reactions could be used and the hippurate cleavage reaction has to be c arried out additionally. Using cultural and biochemical methods, it was pos sible to assign the type and reference strains to the correct species, as w ell as 46 of 47 field isolates could be identified including all five known intestinal Serpulina species from swine. 27 strains were determined as S. hyodysenteriae, nine of these isolates atypically being indole negative. In contrast one canine S, pilosicoli strain was atypical showing indole produ ction. Therefore incidence of indole negative variants of S. hyodysenteriae as well as indole positive S. pilosicoli isolates must be taken into consi deration.