Potential use of a transposon Tn916-generated mutant of Aeromonas hydrophila J-1 defective in some exoproducts as a live attenuated vaccine.

Aeromonas hydrophila is a Gram-negative opportunistic pathogen that causes disease in a wide range of hosts due to its multifactorial virulence. Here we describe the application of transposon insertion mutagenesis approach to obtain an exoenzyme mutant of A. hydrophila strain J-1. Immunization of swordtail fish (Xiphophorus helleri Heckel) with the highly attenuated mutant provided protection (survival of 27 out of 35 fish, compared to survival of only 13 out of 35 control fish) in the fish given the highest immunization dose (10(7) CFU) against intraperitoneal challenge with the wild J-1 strain. Immunization with doses of 10(5) or 10(3) did not provide significant protection.