title: Development of a SYBR green I real-time PCR assay for specific identification of the fish pathogen Aeromonas salmonicida subspecies salmonicida.
abstract: A SYBR Green I real-time polymerase chain reaction protocol for specific detection of the fish pathogen Aeromonas salmonicida subsp. salmonicida was developed and validated for rapid diagnosis of typical furunculosis. The sequence of the aopO gene of A. salmonicida subsp. salmonicida, which encodes for a serine/threonine protein kinase linked to virulence, was chosen for primer design. The selected primers amplified a 119-bp internal fragment of the aopO gene. The specificity test proved that 100 % (40/40) of the A. salmonicida subsp. salmonicida strains tested showed a positive amplification with subspecies-specific melting temperatures (Tm) of 80.75 ± 0.35 °C. Atypical A. salmonicida subspecies and other non-related bacterial fish pathogens did not amplify or showed unspecific melting profiles, except for one strain of A. salmonicida subsp. achromogenes and one strain of A. salmonicida subsp. smithia. The detection sensitivity was 21 fg of purified bacterial DNA per reaction, corresponding to 1-2 bacterial cells and 6-60 bacteria per reaction for seeded kidney and blood. The assay was highly reproducible with low variation coefficient values for intra-run and inter-run assays. The assay also allowed the specific detection of A. salmonicida subsp. salmonicida in tissues of fish naturally and experimentally infected. No amplification was detected when tissues from healthy fish or fish affected by other diseases were tested. The SYBR Green real-time PCR and melt curve analysis developed in this study is a rapid and accurate method for the specific identification of A. salmonicida subsp. salmonicida isolates and its detection on tissues of fish affected by furunculosis.
authors.affiliation: Departamento de Microbiología y Parasitología, Edificio CIBUS Facultad de Biología and Instituto de Investigación y Análisis Alimentario, Universidad de Santiago de Compostela, 15782, Santiago de Compostela, Spain. clara.fernandez.alv@gmail.com.
authors.forename: Clara
authors.initials: C
authors.lastname: Fernández-Álvarez
authors.affiliation: Institute for Research in Biomedicine, Università della Suvizzera Italiana, 6500, Bellinzona, Switzerland.
authors.forename: Santiago F
authors.initials: SF
authors.lastname: González
authors.affiliation: Departamento de Microbiología y Parasitología, Edificio CIBUS Facultad de Biología and Instituto de Investigación y Análisis Alimentario, Universidad de Santiago de Compostela, 15782, Santiago de Compostela, Spain.
authors.forename: Ysabel
authors.initials: Y
authors.lastname: Santos
mesh_terms: D048409:Aeromonas salmonicida / Q000235:genetics / Q000302:isolation & purification*; D000818:Animals; D052160:Benzothiazoles; D017931:DNA Primers / Q000235:genetics; D003959:Diamines; D005393:Fish Diseases / Q000175:diagnosis* / Q000382:microbiology; D005667:Furunculosis / Q000175:diagnosis* / Q000382:microbiology; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D009930:Organic Chemicals / Q000032:analysis*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D011804:Quinolines; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013194:Staining and Labeling / Q000379:methods*; D013696:Temperature; D014730:Veterinary Medicine / Q000379:methods; D037521:Virulence Factors / Q000235:genetics
chemical_list: D052160:Benzothiazoles; D017931:DNA Primers; D003959:Diamines; D009930:Organic Chemicals; D011804:Quinolines; D037521:Virulence Factors; C098022:SYBR Green I; D017346:Protein Serine-Threonine Kinases
keywords: Aeromonas salmonicida subsp. salmonicida; Diagnosis; Real-time PCR; SYBR green; Typical furunculosis; aopO gene