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Lactococcosis in Silver Carp
Author(s) -
Khoo Lester H.,
Austin Frank W.,
Quiniou Sylvie M. A.,
Gaunt Patricia S.,
Riecke Dennis K.,
Jacobs Alicia M.,
Meals Keith O.,
Dunn Arthur W.,
Griffin Matt J.
Publication year - 2014
Publication title -
journal of aquatic animal health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 52
eISSN - 1548-8667
pISSN - 0899-7659
DOI - 10.1080/08997659.2013.837118
Subject(s) - biology , microbiology and biotechnology , 16s ribosomal rna , silver carp , locus (genetics) , pathology , genetics , gene , fish <actinopterygii> , fishery , medicine
An adult Silver Carp Hypophthalmichthys molitrix with a focally extensive skin lesion near the caudal peduncle and mild iridial hemorrhage was submitted to the Aquatic Research and Diagnostic Laboratory (ARDL) in Stoneville, Mississippi, as part of a fish kill investigation. Touch impressions of this musculoskeletal lesion revealed small cocci (∼1 μm) in pairs or chains within an inflammatory milieu. A pure Gram‐positive cocci isolate was obtained from the brain, while cultures of the kidney and muscle yielded multiple bacterial colony types, including the Gram‐positive cocci seen in the brain. This brain isolate was characterized biochemically and identified as Lactococcus spp. Analysis of the near complete 16S small subunit ribosomal DNA (SSU rDNA) and DNA gyrase subunit B ( gyrB ) gene sequences revealed the bacterium to be L. lactis subsp. lactis (SSU rDNA: 100% identity, 1,372/1,372 bp; gyrB : 99.7% identity, 1,779/1,785 bp). Comparatively, at the gyrB locus the case isolate shared less than 90% similarity to L. lactis subsp. cremoris (1,599/1,781 bp) and less than 80% homology to L. garvieae (1409/1775 bp). Histopathological examination confirmed a severe meningoencephalitis, a moderate mononuclear myositis, and a mild interstitial nephritis. We believe this represents the first report of a natural infection by L. lactis subsp. lactis in Silver Carp. Received December 3, 2012; accepted August 17, 2013