Isolation, Identification, and Characterization of Aeromonas veronii from Chinese Soft-Shelled Turtle (Trionyx sinensis)

Aeromonas veronii is widespread in aquatic environments and is capable of infecting various aquatic organisms. A. veronii infection is lethal for Chinese soft-shelled turtles (Trionyx sinensis, CSST). We isolated a gram-negative bacterium from the liver of diseased CSSTs, which was named XC-1908. This isolate was identified as A. veronii based on its morphological and biochemical characteristics, and 16S rRNA gene sequence analysis. A. veronii was pathogenic for CSSTs with an LD50 of 4.17 x 10(5) CFU/g. The symptoms of CSSTs artificially infected with isolate XC-1908 were consistent with those of the naturally infected CSSTs. The levels of total protein, albumin, and white globule in the serum samples of the diseased turtles were decreased, whereas those of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase were elevated. Moreover, the diseased CSSTs exhibited the following histopathological changes: the liver contained numerous melanomacrophage centers, renal glomerulus were edematous, intestinal villi were shed, and in oocytes, the number of vacuoles increased and red-rounded particles were observed. Antibiotic sensitivity tests revealed that the bacterium was sensitive to ceftriaxone, doxycycline, florfenicol, cefradine, and gentamicin, and resistant to sulfanilamide, carbenicillin, benzathine, clindamycin, erythromycin, and streptomycin. This study provides control strategies to prevent outbreaks of A. veronii infection in CSSTs.

Automated summary

Aeromonas veronii is a gram-negative bacterium that can be found in many aquatic environments and is capable of infecting various aquatic organisms. In this study, we isolated a bacterium named XC-1908 from the liver of Chinese soft-shelled turtles, which was identified as A. veronii based on its characteristics and genetic analysis. The bacterium was pathogenic for the turtles, causing symptoms and histopathological changes consistent with natural infections. Antibiotic sensitivity tests showed that the bacterium was sensitive to certain antibiotics while resistant to others. This study provides strategies for preventing outbreaks of A. veronii infection in Chinese soft-shelled turtles.