Non-destructive Molecular Detection of Streptococcus agalactiae in Rainbow Trout (Oncorhynchus mykiss)

Farid, Mehrnoosh; Mirvaghefi, Alireza; Farahmand, Hamid; Nematollahi, Mohammad Ali

doi:10.22059/jfisheries.2018.122229.830

Non-destructive Molecular Detection of Streptococcus agalactiae in Rainbow Trout (Oncorhynchus mykiss)

Document Type : Research Paper

Authors

Mehrnoosh Farid ¹

Alireza Mirvaghefi ²

Hamid Farahmand ²

Mohammad Ali Nematollahi ³

¹ M.Sc. Graduate, Department of Fisheries, Faculty of Natural Resources, University of Tehran, Karaj, Iran.

² Professor, Department of Fisheries, Faculty of Natural Resources, University of Tehran, Karaj, Iran.

³ Associate professor, Department of Fisheries, Faculty of Natural Resources, University of Tehran, Karaj, Iran.

10.22059/jfisheries.2018.122229.830

Abstract

The objective of this study was to evaluate a non-lethal sampling technique to detect Streptococcus agalactiae, the bacterial pathogen causing Streptococcosis, in the blood and mucus of the infected rainbow trout, Oncorhynchus mykiss. Detection was established by PCR protocol based on the scpB gene. Also biochemical identification method was set by API strepsystem and conventional bacteriological tests. The fish were infected by intraperitoneally (i.p.) with 8×10⁷ CFU/ml colony forming units of S. agalactiae. The PCR and biochemical method were positive for the blood samples from 3^th and 4^th days after exposure up to the end of the experiment while the fish look healthy. Mucus samples in PCR assay and biochemical methods were not positive until the end of the experiment. All any biochemically positive results were positive in PCR protocol, but some PCR positive results were negative in biochemical method. PCR Sensitivity tests were done in fish tissues seeded with serial dilutions of pure culture of S. agalactiae. Mucus was not efficient when the bacteria count is low. This study revealed that a nonlethal blood sampling can be used with high efficiency primers for PCR protocol to detect S. agalactiae in asymptomatic fish.

Keywords

Molecular diagnostic method

PCR

Mucus

Blood

diseases

Subjects