| Nonrice isolates were generally avirulent or weakly pathogenic toward rice. |
| Some avirulent isolates also became virulent after their inoculation in resistant rice varieties. |
| It is now possible to differentiate environmental strains of V. cholerae and V. parahaemolyticus between virulent and avirulent strains based on their ability or inability to produce their major virulence factors. |
| Cross-protection between virulent isolates of serologically different strains is usually complete, but avirulent isolates do not afford protection. |
| Griffith found that mice inoculated with either the heat-killed virulent bacteria or the living avirulent bacteria remained free of infection, but mice inoculated with a mixture of both became infected and died. |
| A Lawsonia intracellularis avirulent live culture vaccine used via drinking water. |
