TABLE 2.
Screening for attenutated PhoA+ mutants of E. tarda PPD130/91 with fish as a model
| Strain(s) | No. of fish deada (% mortality) | Description |
|---|---|---|
| E. tarda PPD130/91 | 6 (100) | Virulent |
| E. tarda PPD125/87 | 0 (0) | Avirulent |
| 402 PhoA+ mutants | 6 (100) | |
| 40 PhoA+ mutants | 5 (83) | |
| 14 PhoA+ mutants | 4 (67) | |
| 13 PhoA+ mutants | 3 (50) | |
| 6 PhoA+ mutants | 2 (33) | |
| 4 PhoA+ mutants | 1 (17) | Slightly attenuated |
| 11 PhoA+ mutants | 0 (0) | Moderately and highly attenuated |
a
All of the strains were individually injected intramuscularly into six gourami fish at 106 CFU, and the mortality was recorded at 7 days postinjection.