First Isolation and Identification of Aeromonas veronii in a Captive Giant Panda (Ailuropoda melanoleuca)

SIMPLE SUMMARY: Aeromonas veronii, an important aquatic bacterium, has been known to infect a variety of animals worldwide. However, there have been no reports of A. veronii infection in giant pandas. Here, we found that strain VGP was resistant to six antibiotics, carries a large number of resistance genes and virulence genes, and has strong pathogenicity in mice. These results suggest that infection with strain VGP could be one of the leading causes of death for this giant panda cub. Our study presents the first evidence that giant pandas could be infected by A. veronii. ABSTRACT: The objective of this study was to understand biological characteristics of one bacteria strain named as VPG which was isolated from multiple organs of a dead captive giant panda cub. Here, we use biochemical tests, 16S rRNA and gyrB genes for bacterial identification, the disk diffusion method for antibiotic resistance phenotype, smart chip real-time PCR for the antibiotic resistance genotype, multiplex PCR for determination of virulence genes, and the acute toxicity test in mice for testing the pathogenicity of isolates. The isolate was identified as A. veronii strain based on the biochemical properties and genetic analysis. We found that the strain carried 31 antibiotic resistance genes, revealed antimicrobial resistance phenotypically to several antibiotics including penicillin, ampicillin, oxacillin, amoxicillin, imipenem, and vancomycin, and carried virulence genes including aer, act, lip, exu, ser, luxs, and tapA. The main pathological changes in giant panda were congestion, necrotic lesions and a large number of bacteria in multiple organs. In addition, the LD(50) in Kunming mice infected with strain VGP was 5.14 × 10(7) CFU/mL by intraperitoneal injection. Infection with strain VGP led to considerable histological lesions such as hemorrhage of internal organs, necrosis of lymphocytes and neurons in Kunming mice. Taken together, these results suggest that infection with strain VGP would be an important causes of death in this giant panda cub.