title: Detection and quantification of Aeromonas salmonicida in fish tissue by real-time PCR.
abstract: Furunculosis, a septicaemic infection caused by the bacterium Aeromonas salmonicida subsp. salmonicida, currently causes problems in Danish seawater rainbow trout production. Detection has mainly been achieved by bacterial culture, but more rapid and sensitive methods are needed. A previously developed real-time PCR assay targeting the plasmid encoded aopP gene of A. salmonicida was, in parallel with culturing, used for the examination of five organs of 40 fish from Danish freshwater and seawater farms. Real-time PCR showed overall a higher frequency of positives than culturing (65% of positive fish by real-time PCR compared to 30% by a culture approach). Also, no real-time PCR-negative samples were found positive by culturing. A. salmonicida was detected by real-time PCR, though not by culturing, in freshwater fish showing no signs of furunculosis, indicating possible presence of carrier fish. In seawater fish examined after an outbreak and antibiotics treatment, real-time PCR showed the presence of the bacterium in all examined organs (1-482 genomic units mg-1). With a limit of detection of 40 target copies (1-2 genomic units) per reaction, a high reproducibility and an excellent efficiency, the present real-time PCR assay provides a sensitive tool for the detection of A. salmonicida.
authors.affiliation: National Veterinary Institute, Section for Bacteriology and Pathology, Technical University of Denmark, Frederiksberg C, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Bartkova
authors.affiliation: National Veterinary Institute, Section for Bacteriology and Pathology, Technical University of Denmark, Frederiksberg C, Denmark.
authors.forename: B
authors.initials: B
authors.lastname: Kokotovic
authors.affiliation: Department of Animal Science, Aarhus University, Aarhus N, Denmark.
authors.forename: H F
authors.initials: HF
authors.lastname: Skall
authors.affiliation: Department of Animal Science, Aarhus University, Aarhus N, Denmark.
authors.forename: N
authors.initials: N
authors.lastname: Lorenzen
authors.affiliation: National Veterinary Institute, Section for Bacteriology and Pathology, Technical University of Denmark, Frederiksberg C, Denmark.
authors.forename: I
authors.initials: I
authors.lastname: Dalsgaard
mesh_terms: D048409:Aeromonas salmonicida / Q000235:genetics / Q000302:isolation & purification*; D000818:Animals; D003718:Denmark / Q000453:epidemiology; D005667:Furunculosis / Q000453:epidemiology* / Q000382:microbiology; D016905:Gram-Negative Bacterial Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D017686:Oncorhynchus mykiss; D010274:Parasitology / Q000379:methods*; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary*; D015203:Reproducibility of Results; D017422:Sequence Analysis, DNA / Q000662:veterinary; D014018:Tissue Distribution
keywords: 
  Aeromonas salmonicida
  ; 
  aopP
  ; furunculosis; pAsal1; rainbow trout; real-time PCR