First Isolation of Vagococcus Salmoninarum From Cultured Rainbow Trout (Oncorhynchus Mykiss, Walbaum) Broodstocks in Turkey

Abstract

In this study, we isolated Vagococcus salmoninarum for the first time from rainbow trout in Turkey. The disease outbreak occurred in post-spawning broodstocks at a water temperature of 12.6°C during March-April 2011. The cumulative mortality rate was approximately 55% within 2 months. Infected trout exhibited lethargy, a marked loss of equilibrium, anorexia, dark coloration, mono and bilateral exophthalmos, eyeball disruption, furuncles and erosive lesions on both sides of the body, hemorrhage in the abdomen, jaw, mouth, and anus, and prolapse of the anus. Necropsy findings included hyperemia, visceral hemorrhage, and fibrinous deposits in the heart (ventricle and atrium), liver, and spleen. Samples for bacteriological examinations were collected from the kidney, liver, spleen, and ovary by using sterile swabs; these samples were streaked onto trypticase soy agar plates, and incubated at 22°C for 48 h. Four bacterial isolates were obtained from sick fish. The Gram-positive V. salmoninarum isolates were identified by their morphological, physiological, and biochemical features. The identification was confirmed by PCR with the amplification of highly specific 16S rRNA gene for V. salmoninarum. Although the isolates were sensitive to erythromycin and doxycycline in vitro; antibiotic treatments were ineffective.