FIG. 3.

Competitive assays of selected STM mutants. CIs are calculated against S. iniae wild-type strain 9117, as described in Materials and Methods. CI is defined as the output ratio (mutant/wild type) divided by the input ratio (mutant/wild type). A CI of less than 1 indicates a quantitative degree of attenuation in virulence of the mutant compared to the virulence of the wild type. CIs were determined individually for mutant strains recovered from both hearts and brains for each STM mutant assayed. Each triangle represents one individual fish experiment. The mean of all CI experiments is listed beneath each mutant label, along with the P value in comparison to the wild-type value. Black bars indicate mean values in eight individual fish experiments.