Three species of Aeromonas (A. dhakensis, A. hydrophila, and A. jandaei) isolated from freshwater crocodiles (Crocodylus siamensis) with pneumonia and septicemia.

Hundreds of farmed Siamese crocodiles (Crocodylus siamensis) died during July 2016 at a farm in Wenchang, Hainan, China. In two necropsied crocodiles, we observed symptoms of dermatorrhagia, hepatomegaly and hepatic congestion. Pulmonitis was diagnosed by pulmonary congestion and pulmonary fibrinous exudate. Septicaemia was diagnosed by isolation of three Aeromonas species from blood and visceral tissues; A. dhakensis, A. hydrophila, and A. jandaei were identified by biochemical and molecular tests. We used a zebrafish model to determine the half-maximal lethal dose (LD50 ), and A. dhakensis was found to be the most virulent species, with an LD50 of 8.91 × 105 CFU/ml. The results of a drug sensitivity test indicated that these species were sensitive to 11 antibiotics. This is the first report of A. dhakensis, A. hydrophila, and A. jandaei being isolated from a mixed infection in Siamese crocodiles. This article is protected by copyright. All rights reserved.