*2.2. FabF8:Stx2 Neutralizes the Cytotoxic Effect of Supernatants from Different Stx2-Producing Strains*

The FabF8:Stx2 was employed in a gold standard Vero cell assay (VCA) to test its neutralization ability to the toxicity of the supernatants from different STEC strains producing Stx2 or Stx1/2. The ability of this antibody in neutralizing the purified Stx2 was 84% (Table 1). Bacterial supernatant cytotoxicity was tested in the absence and presence of FabF8:Stx2 (Figure 2). It was observed that 85% of the tested supernatants were neutralized (from 7 to 100%), in 20 strains this rate was above 20% and this ability was superior to 40% in 16 strains. Therefore, the FabF8:Stx2 neutralizing ability ranged from 0 to 100%. No significant differences were observed in its neutralizing ability against Stx2 or Stx1/Stx2 producing strains. This recombinant antibody failed to neutralize only four strains, none of them producing just Stx2a (Figure 2, Table 1).

**Table 1.** Stx-producing strains features.


**Table 1.** *Cont.*


ND—not determined; NT—not typeable.

**Figure 2.** Percentage of cytotoxicity of STEC supernatants from strains bearing *stx2* or *stx1/2* genes; in absence (white bars) and in presence of FabF8:Stx2 (flared bars). Data represents biological duplicates of three independent experiments.
