The determination of the infectious status and prevalence of motile Aeromonas species isolated from disease cases in rainbow trout (Oncorhynchus mykiss) and aquarium fish.

The aims of this study were to determine the prevalence and phylogenetic relationship of motile Aeromonas spp. that might be pathogenic species for rainbow trout in infected/mix infection cases (based upon different outbreaks on fish farms). A total of 99 motile Aeromonas isolates (and three reference strains) were analysed that were isolated from four different fish species in different sizes of fish (0.1-3,000 g), different months and water temperatures (6.1-21.2°C). The biochemical characteristics of the isolates were determined using conventional tests and a rapid test kit. Additionally, molecular identification was performed using the gyrB housekeeping gene region and with glycerophospholipid-cholesterol acyltransferase polymerase chain reaction (GCAT-PCR). The sequencing results obtained from the gyrB gene region were deposited in the GenBank database, and phylogenetic relationships were determined with the BioNumerics 7.6 database. Nearly half of the Aeromonas isolates that were isolated from rainbow trout showing signs of disease were determined to be possible infectious agents. Aeromonas species exhibit biochemical variability for many characters, so some Aeromonas species tested negative for GCAT-PCR despite that this test was created especially for Aeromonas identification. The phylogenetic tree based upon gyrB contained 10 different phylogroups that were based on 96% cut-off value in gyrB gene region.