Isolation and characterisation of four distinct cytotoxic factors of Salmonella Weltevreden

Four distinct cytotoxins with different biological, physico-chemical and an tigenic characteristics were isolated from a single Salmonella Weltevreden strain recovered from buffalo meat. The toxins were purified by means of sa lt precipitation, dialysis, gel filtration and ion-exchange chromatographic methods. Cytotoxin I was dermonecrotic, verocytotoxic and lethal for the m ouse (LD50 120 mu g). It induced accumulation of serosanguinous fluid in th e rabbit ligated ileal loop (RLIL) and mucinous fluid in the stomach. It wa s active within a narrow pH range (5.0 - 8.0) and lost its activity on auto claving for 1 min. Cytotoxin II was verocytotoxic, enterotoxic and lethal t o 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 de grees C, 30 min). Cytotoxin III was neither dermatotoxic nor enterotoxic. I t induced vacuolation, multinucleation and formation of syncytia in Vero ce lls. 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 t o rabbit skin within 6 h of inoculation and lysed Vero cells. It also posse ssed haemolytic and lecithinase/phospholipase-C activities. The cytotoxin l ost its activity on heating at 90 degrees C (30 min) but remained active be tween 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 t he homologous cytotoxin and did not cross-react with heterologous cytotoxin s.