Although the bacterial densities in all immersion
treatments were adjusted to 2 × 108 cells ml−1, the
different media types used to grow the bacteria gave
different results. The immersion treatment with
mixed culture A grown in liquid media (TSB+)
caused typical AHPNS gross signs and mortalities in
experimental shrimp within 18 h after exposure.
Upon histological examination of fixed samples,
100% of the samples in the TSB+ treatment were
positive for AHPNS pathology at high severity grades
(G3−4). In contrast, all treatments with the same
mixed culture A grown on solid media did not induce
any AHPNS gross signs until 3 d after exposure, and
no mortalities were recorded.