title: An adult zebrafish model for Laribacter hongkongensis infection: Koch's postulates fulfilled.
abstract: Laribacter hongkongensis is a gram-negative emerging bacterium associated with invasive bacteremic infections in patients with liver disease and fish-borne community-acquired gastroenteritis and traveler's diarrhea. Although the complete genome of L. hongkongensis has been sequenced, no animal model is available for further study of its pathogenicity mechanisms. In this study, we showed that adult zebrafish infected with L. hongkongensis by immersion following dermal abrasion or intraperitoneal injection suffered mortality in a dose-dependent manner, with lethal dose 50 (LD50) of 2.1×10(4) and 1.9×10(4) colony-forming units (CFU)/mL, respectively. All mortalities occurred in the first four days post-infection. Zebrafish that died showed characteristic clinicopathological features: swimming near water surface, marked lethargy and sidestroke; abdominal hemorrhage, ulcers and marked swelling with ascites; and hydropic degeneration and necrosis of hepatocytes around central vein and inflammatory cells infiltration. L. hongkongensis was recovered from the ascitic fluid and tissues of zebrafish that died. Of the 30 zebrafish infected with 2.1×10(4) CFU/mL (LD50) L. hongkongensis isolated from dead zebrafish using the immersion following dermal abrasion method, 18 (60%) died. All zebrafish that died also showed the characteristic clinical and pathological features. Histopathological studies also showed dilation of hepatic central vein and hydropic degeneration. L. hongkongensis was isolated from the zebrafish that died. The Koch's postulates for L. hongkongensis as an infectious agent have been fulfilled. This highly reproducible and effective zebrafish model is of crucial importance for future studies on virulence factors for L. hongkongensis infection.
authors.affiliation: The Second Clinical Medical College, Southern Medical University , Guangzhou 510515, Guangdong Province, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Xie
authors.affiliation: The Second Clinical Medical College, Southern Medical University , Guangzhou 510515, Guangdong Province, China.
authors.forename: Jia-Bei
authors.initials: JB
authors.lastname: He
authors.affiliation: The First Clinical Medical College, Southern Medical University , Guangzhou 510515, Guangdong Province, China.
authors.forename: Jia-Wei
authors.initials: JW
authors.lastname: Shi
authors.affiliation: Biosafety Level-3 Laboratory, School of Public Health and Tropical Medicine, Southern Medical University , Guangzhou 510515, Guangdong Province, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Xiao
authors.affiliation: Biosafety Level-3 Laboratory, School of Public Health and Tropical Medicine, Southern Medical University , Guangzhou 510515, Guangdong Province, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.affiliation: State Key Laboratory of Emerging Infectious Diseases, Department of Microbiology, The University of Hong Kong , Hong Kong, China.
authors.forename: Patrick Cy
authors.initials: PC
authors.lastname: Woo
keywords: Laribacter hongkongensis; animal model; infection