We report here on the isolation of isogenic strains of Aeromonas hydrophila AB3 deleted for a segment of the aerolysin gene. All aer mutants obtained lacked the 49-kilodalton aerolysin gene product and were neither hemolytic for blood erythrocytes nor cytotoxic for Chinese hamster ovary tissue culture cells. One such mutant, AB3-5, was used in a mouse toxicity model to evaluate the role of aerolysin in the pathogenesis of A. hydrophila infections. The strain had a 50% lethal dose (LD50) of greater than 10(9) as compared with the parental strain which had an LD50 of 5 X 10(7). Reintegration of the deleted segment into AB3-5 resulted in an LD50 of 6 X 10(7) cells for this revertant. Furthermore, all mice injected with a sublethal dose of the parental strains developed necrotic lesions; this was never obtained with the aerolysin-deficient strain AB3-5. More importantly, specific neutralizing antibody to aerolysin was detected in mice surviving A. hydrophila infection, demonstrating that aerolysin is produced during the course of systemic A. hydrophila infections.

Chakraborty, T., Huhle, B., Hof, H., Bergbauer, H., & Goebel, W. (1987). Marker exchange mutagenesis of the aerolysin determinant in Aeromonas hydrophila demonstrates the role of aerolysin in A. hydrophila-associated systemic infections. Infection and Immunity, 55(9), 2274–2280.