Characteristics of disease spectrum in relation to species, serogroups, and adhesion ability of motile aeromonads in fish

Abstract

An attempt was made to delineate the relationship between of Aeromonas species and/or serogroups and specific disease symptoms in common carp Cyprinus carpio L. and rainbow trout Oncorhynchus mykiss Walbaum. The adhesion of Aeromonas strains to various tissues in relation to disease spectrum was also tested. All strains of A. hydrophila caused skin ulcers as well as septicaemia in both carp and trout while the other strains were able to cause only skin ulcers or some specific internal lesions with or without septicaemia depending on which species and/or serogroup they represented. Disease symptoms depended also on fish species. It was found that adhesion intensity of Aeromonas strains tested was significantly higher to tissues, which were susceptible to infection with these strains. The results indicate that adhesion to various cells of the fish organism is principal marker to detect virulent Aeromonas strains. The findings presented in this study may be helpful in the appraisal of aeromonads disease risk and kind of the infection in particular fish farms by epizootiological studies or/and during routine fish examinations. They will also be useful to improve and facilitate diagnosis of bacterial fish disease.

Figure 1

Ulcers in carps Sc challenged with A. hydrophila strain Pt39 (a) and A. bestiarum strain J4N (b). Very deep ulcer exposing skeleton after injection of A. bestiarum.

Figure 2

Skin ulcer penetrating deep into the muscle in trout Sc challenged with A. hydrophila Pt104.

Figure 3

Extensive dermatitis in carp Sc challenged with A. veronii bt. sobria strains Pt 57 (a) and K48 (b). Distended anus (arrow) was the first symptom of septicaemia.

Figure 4

Septicaemia in fish Ip challenged with A. veronii bt. sobria strain K151 (a) and A. hydrophila strain Pt104 (b): exophthalmia, swelling of abdomen, and intensive congestions on the body surface in carp (a); enlarged spleen, intensive congestions, and liquefaction of internal organs in trout (b).

Figure 5

Control slides covered with homogenized carp skin mucus (a), trout liver (b), and carp blood (c): no bacterial cells are visible.

Figure 6

Numerous bacterial cells of A. veronii bt. sobria strain K48 adhering to carp mucus and epidermal cells (a) and carp kidney (b).

Figure 7

Numerous bacterial cells of A. hydrophila strain Pt104 (a) adhering to trout liver (a) and isolated bacterial cells of A. sobria strain K24 adhering to carp kidney (b).

Figure 8

Numerous bacterial cells of A. hydrophila strain Pt 104 (a) and isolated cells of A. veronii bt. sobria strain W62 (b) adhering to trout blood cells.