Description of a pathogenic strain of Aeromonas dhakensis isolated from Ancherythroculter nigrocauda in an inland region of China.

Aeromonas dhakensis is reported as an emerging pathogenic species within the genus Aeromonas and is widely distributed in tropical coastal areas. This study provided a detailed description and characterization of a strain of A. dhakensis (202108B1) isolated from diseased Ancherythroculter nigrocauda in an inland region of China. Biochemical tests identified the isolate at the genus level, and the further molecular analysis of concatenated housekeeping gene sequences revealed that the strain belonged to the species A. dhakensis. The isolated A. dhakensis strain was resistant to five antibiotics, namely, penicillin, ampicillin, clindamycin, cephalexin and imipenem, while it was susceptible or showed intermediate resistance to most of the other fifteen tested antibiotics. The isolated strain of A. dhakensis caused acute haemorrhagic septicaemia and tissue damage in artificially infected A. nigrocauda, with a median lethal dose of 7.76×104 CFU/fish. The genome size of strain 202108B1 was 5043286 bp, including one chromosome and four plasmids. This is the first detailed report of the occurrence of infection caused by an A. dhakensis strain causing infection in an aquaculture system in inland China, providing important epidemiological data on this potential pathogenic species.