antibody therapy she experiences no relapse an 87 year old female develops bronchopneumonia while resident in long stay care facilities the local general practitioner starts her on a course of antibiotic therapy with immediate benefit however eight days after stopping the antibiotic she experiences severe diarrhoea her condition starts to deteriorate necessitating admission to hospital where toxin a is detected in her faeces by an elisa test by this time she is extremely ill with evidence of circulatory failure and her diarrhoea has stopped the latter is found to be due a combination of paralytic ileus and toxic megacolon and an emergency total colectomy is considered essential since such surgery is associated with a mortality in excess of 60 she receives intravenous replacement therapy together with the contents of two ampoules 500 mg of antibody product by the time she is taken to the operating theatre four hours later her general condition had improved significantly and she survives surgery for each antigen 5 doses of 100 u03bcg were given monthly to each of 3 sheep and the serum analysed at 18 weeks elisa titres derived from 14 week samples represent serum dilutions pool from 3 animals which gave a signal of 0 5 a 450 above background and are the mean of duplicate determinations for the crystal violet ed 50 assay toxin b was used at a fixed concentration of 2 ng ml and toxin a at 50 ng ml antibodies to toxin b residues 767 1852 toxinotype 0 sequence were assessed for their capacity to neutralise other toxin b toxinotypes purified toxin b toxinotypes 0 3 5 and 10 were each titrated in the cell assay and used at a fixed concentration of 16 u00d7 the minimum toxin concentration which causes cell.