Isolation and characterisation of four distinct cytotoxic factors of Salmonella Weltevreden.

Four distinct cytotoxins with different biological, physico-chemical and antigenic characteristics were isolated from a single Salmonella Weltevreden strain recovered from buffalo meat. The toxins were purified by means of salt precipitation, dialysis, gel filtration and ion-exchange chromatographic methods. Cytotoxin I was dermonecrotic, verocytotoxic and lethal for the mouse (LD50 120 micrograms). It induced accumulation of serosanguinous fluid in the rabbit ligated ileal loop (RLIL) and mucinous fluid in the stomach. It was active within a narrow pH range (5.0-8.0) and lost its activity on autoclaving for 1 min. Cytotoxin II was verocytotoxic, enterotoxic and lethal to for the mouse (LD50, 1 mg). It induced delayed vasopermeability in rabbit skin, was active at between pH 5.6 and 8.4 only and heat-sensitive (100 degrees C, 30 min). Cytotoxin III was neither dermatotoxic nor enterotoxic. It induced vacuolation, multinucleation and formation of syncytia in Vero cells. It was pH-sensitive beyond the range of 4.8 to 8.2. It was completely inactivated on boiling for 30 min. Cytotoxin IV was intensely necrotizing to rabbit skin within 6 h of inoculation and lysed Vero cells. It also possessed haemolytic and lecithinase/phospholipase-C activities. The cytotoxin lost its activity on heating at 90 degrees C (30 min) but remained active between pH 2.5 and 7.5. The PIs of the cytotoxins were estimated to be 9.0, 7.0, 5.6 and 3.0, respectively. All the four cytotoxins were immunogenic in rabbits but antigenically unrelated as the anticytotoxin neutralized only the homologous cytotoxin and did not cross-react with heterologous cytotoxins.