[Identification and drug sensitivity of a Plesiomonas shigelloides isolated from diseased sturgeons]

In 2012, the cumulative mortality of farmed sturgeons in Beijing was almost 60% with various symptoms, including the reddening of the anus with yellow exudation, ascities in the peritoneal cavity, petechial haemorrhages in liver and internal muscle wall, and the swollen spleen.

We isolated the pathogen from the dying sturgeons with significant pathological signs, and then analyzed its morphological, physiological and biochemical characteristics, taxonomic status, and drug sensitivity. Moreover, the pathogenic characteristic of presumptive pathogens was identified by artificial infection.

The 16S rDNA sequence of the pathogen was more than 99% homology with that of Plesiomonas shigelloides, suggesting that the pathogen was P. shigelloides, which was also demonstrated by the results of biochemical tests. The LD50 of the pathogen to sturgeon was 1.0 x 10(5.8) CFU/mL, and it also can cause liver, kidey and spleen to lesions. There were no activities of amylase, caseinase, lipase, gelatinase and haemolysis of extracellular products of P. shigelloides, and its toxicity might be from endotoxin. In addition, the bacterium was specific sensitive to enrofloxacin, doxycyline hyclate, florfenicol and thiamphenicol with MIC less than 2 microg/mL.

P. shigelloides was the main pathogen to cultured sturgeons in Beijing area, and enrofloxacin, doxycyline hyclate and florfenicol can be used against the disease.