Aeromonas hydrophilaandAeromonas veroniicause motileAeromonassepticaemia in the cultured Chinese sucker,Myxocyprinus asiaticus

In August 2017, a serious disease causing high mortality occurred in a Myxocyprinus asiaticus aquaculture farm. According to necropsy findings, bacteriology experiments and phylogenetic analysis based on 16S rRNA, cpn60, gyrB and rpoB genes and concatenated alignment sequences (cpn60, gyrB and rpoB genes), two isolates, that is, BBAh1 and BBAv1, were identified as Aeromonas hydrophila and Aeromonas veronii respectively. Artificial infection experiments were carried out, showing that the BBAh1 and BBAv1 strains can cause similar symptoms and have LD50 values of 1.93×105 and 8.77×105 cfu/g respectively. In addition, some virulent genes coding for AerA, Alt, Ast, AscV, AexT, AspA, HlyA, OmpA, Lip and FlaA were detected in the two strains. Furthermore, BBAh1 and BBAv1 showed the same sensitivities to 28 antibiotics, some of which, such as cefotaxime, aztreonam, ceftriaxone and tetracycline, may be used to control the disease. However, the strains were also resistant to many antibiotics. These results provide a scientific reference for the diagnosis, prevention and treatment of motile Aeromonas septicaemia caused by A. hydrophila or A. veronii in cultured Chinese sucker.