Isolation and Characterization of Virulent Citrobacter freundii Associated with White Muscle Disease in Farmed Red Swamp Crayfish, Procambarus clarkia
Isolation and Characterization of Virulent Citrobacter freundii Associated with White Muscle Disease in Farmed Red Swamp Crayfish, Procambarus clarkia
Hongsen Xu*, Xiaoni Wang, Tie Tian, Changyu Zhao, Denghang Yu and Jun Liu
ABSTRACT
In June 2021, a sudden outbreak of white muscle disease coincidence with considerable mortality was occurred in Procambarus clarkii which were cultured in Jiangxia fish farm, Wuhan, Hubei province, China. A dominant bacterial colony, named FSN1, was isolated by incubating on Luria-Bertani agar. Morphological, physiological and biochemical characterization as well as 16S rRNA sequencing identified FSN1 isolate as Citrobacter freundii. Drug sensitivity test showed the strain has multiple drug resistance and was only sensitive to a few antibiotics (doxycycline, tetracycline, minocycline and ciprofloxacin). PCR amplification of specific genes responsible for antibiotic resistance (extended-spectrum β-lactamases, quinolone resistance determinants and tetracycline-resistance) confirmed antibiotics sensitivity of this bacterium. Artificial infection showed that the strain could cause similar symptoms to those of naturally infected crayfish, and the lethal dose 50% was 1.52 × 106 CFU/g crayfish. Serious histopathological changes, such as cell degeneration and necrosis, hemorrhage and inflammatory cell infiltration, were found in diseased crayfish. In conclusion, this study confirmed the pathogen of whitish muscle disease in farmed P. clarkii, and preliminarily investigated the biological characteristic, pathogenicity and drug sensitivity of this bacterium. The results of this study will provide scientific guidance for the effective prevention and control of muscle turbidity of P. clarkii.
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