Abstract
A total 291 strains of motile members of the genus Aeromonas were classified according to the taxonomic scheme proposed by POPOFF and VERON (1976). Forty three were indetified as A. hydrophila biovar hydrophila, 9 as A. hydrophila biovar anaerogenes, and 52 as A. sobria. The remaining 187 strains could not be identified. Thirty seven (86%) of 43 A. hydrophila biovar hydrophila, 3 (33 %) of 9 A. hydrophila biovar anaerogenes, 32 (62 %) of 52 A. sobria, and 65 (35%) of the 187 unidentified originated from fishes.
All 6 A. hydrophila biovar hydrophila examined fell in the category of high virulence. The Japanese loach injected with them were killed earlier than those injected with the other motile Aeromonas, and the difference of mean time to death was statistically significant (P<0.01). The difference of average value of proteolytic activity of the broth culture filtrate between A. hydrophila biovar hydrophila and the other was significant (P<0.01), also. Exophthalumus and scale protrusion were evident only among fish injected with the sonicated cell extracts of A. hydrophila biovar hydrophila.
