Cytotoxicity assay (CTA) The CTA for the detection of C. difficile A/B toxins was performed with Vero cells (Vero–ATCC CCL 81). -Briefly faecal samples were diluted 1:4 in phosphate-buffered saline (pH 7.0) and centrifuged at 3000 g 5 min 4°C. -The resulting supernatant filtered through a filter pore size 0.22 mm 2-fold until dilution 1:1024 reached. - Serial dilutions parallel Clostridium sordellii antitoxina added onto cell monolayers. examined after 24 h incubation 37°C an incubator containing air supplemented 5% CO2. A specimen considered positive if least 90% rounded and same sample effect neutralised by antitoxin.