title: Lactococcus lactis subsp. lactis infection in Bester sturgeon, a cultured hybrid of Huso huso × Acipenser ruthenus, in Taiwan.
abstract: Approximately 5300 hybrid sturgeons with an average body weight of 600-800 g were farmed in 3 round tankers measuring 3m in diameter each containing 28,000 L of aerated groundwater. According to the owner's description, the diseased fish had anorexia, pale body color, and reddish spots on the abdomen. The morbidity and lethality rates in this outbreak were about 70% (3706/5300) and 100% (3706/3706), respectively. The clinical examination revealed enteritis, enlarged abdomen, and rapid respiration rate. The gross findings revealed a volume of about 4 mL of ascites. The histopathological examination showed multiple massive, hemorrhagic or coagulative necrotic foci in the liver and spleen. Furthermore, there was diffuse infiltration of glycogen in hepatic cells, and a few polymorphonuclear and mononuclear leucocytes were observed surrounding the spleen. Some bacterial clumps were noted around the necrotic foci. We also observed that there was moderate to severe, acute, multifocal, coagulative necrosis in the renal parenchyma, with some necrotic foci present beneath the margin of the kidney. Additionally, multifocal, coagulative necrosis was found in the pancreas. Results of microbiologic examinations, including biochemical characteristics, PCR amplification of 16S rRNA gene, sequencing and comparison, and phylogenetic analysis, revealed the pathogen of this infection was Lactococcus lactis subsp. lactis, and based on the results of an antimicrobial agent sensitivity test the bacterium was only sensitive to ampicillin and florfenicol. Additionally, results of in vivo experimental infections in hybrid tilapia showed that 1×10(8) and 1×10(9) CFU/mL of our isolate caused death in all fish and LD(50) values ranged from 10(2) to 10(5) CFU/mL. To the best of the authors' knowledge, this is the first reported case of Lactococcus lactis subsp. lactis infection in hybrid sturgeon.
authors.affiliation: Department of Veterinary Medicine, College of Veterinary Medicine, National Chung Hsing University, Taichung City 402, Taiwan.
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Chen
authors.forename: Shao-Wen
authors.initials: SW
authors.lastname: Hung
authors.forename: Ching-Lin
authors.initials: CL
authors.lastname: Shyu
authors.forename: Cheng-Chung
authors.initials: CC
authors.lastname: Lin
authors.forename: Pan-Chen
authors.initials: PC
authors.lastname: Liu
authors.forename: Chen-Hsuan
authors.initials: CH
authors.lastname: Chang
authors.forename: Wei-Yau
authors.initials: WY
authors.lastname: Shia
authors.forename: Ching-Fu
authors.initials: CF
authors.lastname: Cheng
authors.forename: Shiun-Long
authors.initials: SL
authors.lastname: Lin
authors.forename: Ching-Yu
authors.initials: CY
authors.lastname: Tu
authors.forename: Yu-Hsing
authors.initials: YH
authors.lastname: Lin
authors.forename: Way-Shyan
authors.initials: WS
authors.lastname: Wang
mesh_terms: D000818:Animals; D017756:Aquaculture; D001483:Base Sequence; D005393:Fish Diseases / Q000453:epidemiology / Q000382:microbiology* / Q000473:pathology; D005399:Fishes / Q000235:genetics*; D016908:Gram-Positive Bacterial Infections / Q000453:epidemiology / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D013294:Lactococcus lactis / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013624:Taiwan / Q000453:epidemiology; D017210:Tilapia / Q000235:genetics
chemical_list: D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S