Table 1.
Characterization of Ty21a-PA-01 seed bank
| Assay | Method | Vial 1 | Vial 2 | Ty21a | Ty2 | E. coli |
|---|---|---|---|---|---|---|
| Microbiological | API 20 E | S. Typhi | S. Typhi | S. Typhi | S. Typhi | E. coli |
| Colony appearance on Bromothymol blue agar ( + 1% galactose) | Blue | Blue | Blue | Yellow | Blue | |
| Biochemical | Minimal media + cysteine + thiamine + tryptophan | No growth | No growth | No growth | Growth | No growth |
| Minimal media + cysteine + thiamine + tryptophan + valine + isoleucine | Growth | Growth | Growth | Growth | Growth | |
| Heat stress at 55 °C for 20 min | Sensitive | Sensitive | Sensitive | Resistant | Sensitive | |
| Oxidative stress in 0.3% H2O2 for 20 min | Sensitive | Sensitive | Sensitive | Resistant | Sensitive | |
| Galactose (1%) induced bacteriolysis | Sensitive | Sensitive | Sensitive | Resistant | ND | |
| Immunological | 9,12 O-antigen agglutination | + | + | + | + | ND |
| Vi antigen agglutination | − | − | − | + | ND | |
| PA Expression (colony and western blot) | + | + | − | ND | ND | |
| Genetic | 16 S rDNA sequence | Identical to Ty21a | Identical to Ty21a | Ty21a | Ty2 | ND |
| galE DNA sequence | Identical to Ty21a | Identical to Ty21a | Ty21a (T367C; C442Δ) | Ty2 (wild type) | ND | |
| Chromosomally integrated PA expression-secretion cassette (PCR) | + | + | − | − | ND |
Two random vials from the seed bank were characterized.38 Ty21a (Vivotif), S. enterica serovar Typhi strain Ty2, and E. coli strain HB101 were controls