Disease of rainbow trout caused by Pseudomonas luteola Ilhan Altinok a, ⁎ , Fikri Balta b , Erol Capkin a , Sevki Kayis b a Karadeniz Technical University, Faculty of Marine Sciences, 61530 Surmene, Trabzon, Turkey b Rize University, Department of Fisheries and Aquatic Sciences 53100, Rize, Turkey Received 13 August 2007; received in revised form 21 September 2007; accepted 2 October 2007 Abstract Bacteria isolated from rainbow trout, Oncorhynchus mykiss, kept in a farm, in Turkey. During the outbreak, 40% of the rainbow trout (10–40 g) died. Typical clinical signs were exophthalmia, dark pigmentation, hemorrhage at the base of the pectoral, pelvic, anal fins and around the vent. Internal signs were enlarged spleen, pale liver and intestine filled with yellowish fluid. Liver, kidney and spleen of diseased fish, were aseptically streaked on Tryptic Soy Agar. After incubation, pure cultured colonies were observed and biochemically characterized with API 20 NE and other biochemical tests. Cultured bacterial 16 S rDNA gene was sequenced. Based on biochemical characteristics and sequence of 16 S rRNA, the causative bacteria were identified as Pseudomonas luteola. This study reports the first P. luteola infection in fish. © 2007 Elsevier B.V. All rights reserved. Keywords: Pseudomonas infection; Chryseomonas luteola; Histopathology 1. Introduction Pseudomonas luteola, known also as known as Chryseomonas luteola, a Gram-negative rod, is increas- ingly recognized as an important cause of hospital- acquired infections, especially among immunocompro- mised patients (Anzai et al., 1997; Kiska and Gilligan, 1999). P. luteola is aerobic, non-spore-forming, motile, oxidase-negative and catalase-positive (Kiska and Gilligan, 1999). Although the normal habitat of P. luteola is unclear, it is frequently found in soil, on plants, in aqueous environments and other damp environments (Freney et al., 1988; Silver et al., 1985; Hawkins et al., 1991). P. luteola has been known to be associated with human clinical infections, including bacteraemias (Con- nor et al., 1987; Hawkins et al., 1991; Rohav et al., 1995) that occur in association with pancreatic abscess, prosthetic valve endocarditis, peritonitis, osteomyelitis, indwelling vascular catheters and facial cellulites (Rastogi and Sperber, 1998). However it is not a common pathogen in aquaculture and P. luteola infection in fish has not been reported. In the present study, P. luteola infection in rainbow trout, Oncor- hynchus mykiss and biochemical and 16 S rDNA gene properties of P. luteola was described. 2. Methods 2.1. Isolation of bacteria A disease outbreak occurred during the spring of 2004 in a rainbow trout farm, Rize, Turkey. Affected fish size ranged between 10 g and 40 g. Thirty six moribund fish were necropsied. All sampled fish were examined externally and internally. The gills and body surface were examined Available online at www.sciencedirect.com Aquaculture 273 (2007) 393 – 397 www.elsevier.com/locate/aqua-online ⁎ Corresponding author. Tel.: + 90 462 7522805; fax: +90 462 7522158. E-mail address: ialtinok@ktu.edu.tr (I. Altinok). 0044-8486/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2007.10.025