title: Diagnostic tools for rapid detection and quantification of Weissella ceti NC36 infections in rainbow trout.
abstract: Weissellosis of rainbow trout is caused by the Gram-positive bacteria Weissella ceti and has been reported in China, Brazil and the United States. This disease can result in high mortality in market-sized fish and thus can cause significant economic loss. Thus far, phenotypic characterization and 16S rRNA sequencing have been used to confirm a Weissellosis diagnosis. Here, we present the development of PCR-based diagnostic tools for the rapid identification and quantification of W. ceti within bacteriological culture and infected tissues. A duplex PCR, which amplifies both genus- and strain-specific targets, positively identifies isolates as W. ceti NC36. A qPCR assay was also developed to quantify pathogen load from infected tissues, using a W. ceti NC36 unique locus. A proof of concept study was performed to demonstrate that quantification using traditional plate count methods and qPCR were significantly correlated when assessed from infected brain and spleen tissue. These tools were also used to confirm diagnosis of Weissellosis in a commercial rainbow trout farm during an outbreak investigation. These are the first diagnostic tools developed for identification and quantification of W. ceti infection within rainbow trout, contributing to rapid Weissellosis diagnosis, enhanced pathogen surveillance and epidemiological studies.
authors.affiliation: National Center for Cool and Cold Water Aquaculture, Agricultural Research Service/U.S. Department of Agriculture, Kearneysville, WV, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Snyder
authors.affiliation: Department of Applied Ecology, North Carolina State University, Mills River, NC, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Hinshaw
authors.affiliation: National Center for Cool and Cold Water Aquaculture, Agricultural Research Service/U.S. Department of Agriculture, Kearneysville, WV, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Welch
mesh_terms: D000818:Animals; D058491:Bacterial Load; D001921:Brain / Q000382:microbiology; D004196:Disease Outbreaks / Q000662:veterinary; D005393:Fish Diseases / Q000175:diagnosis / Q000382:microbiology*; D016908:Gram-Positive Bacterial Infections / Q000175:diagnosis / Q000382:microbiology / Q000662:veterinary*; D009657:North Carolina / Q000453:epidemiology; D017686:Oncorhynchus mykiss / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary*; D012680:Sensitivity and Specificity; D013154:Spleen / Q000382:microbiology; D058836:Weissella / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D012336:RNA, Ribosomal, 16S
keywords: Weissella ceti strain NC36; Weissellosis; aquaculture; diagnostic tool; rainbow trout