Experimental Infection of Flexibacter maritimus in Black Sea Bream (Acanthopagrus schlegeli) Fry

Abstract

Immersion, subcutaneous injection and smear followed by immersion were studied in black sea bream fry in order to establish an effective method of infection with the gliding bacterium, Flexibacter maritimus. In addition, the occurrence or proliferation of the bacteria on the skin, gills and internal organs (kidney, liver and spleen) were determined by serial plate count dilution from separately homogenized samples. Immersion failed to infect the fish after 3 d of observation whereas, fish infected by smear followed by immersion in 108, 106 and 104 cells/ml showed the symptoms of natural gliding bacteria infection in 23 h post infection. Subcutaneous injection resulted to serious injuries, in 30 h post infection, on the site of injection like exposed musculature leading to heavy mortalities including the control fish. Therefore, subcutaneous injection did not serve a practical means of inducing gliding bacteria infection in this study. The bacteria were detected in greatest number in the skin from 15 min until the 3rd hour, in the gills 1 h up to 12 h, and least detected in the internal organs from 1 h until 12 h post infection. In all cases, the bacteria could not be detected thereafter due to the successive invasion of other bacteria. © 1987, The Japanese Society of Fish Pathology. All rights reserved.