First Evidence of <i>Vibrio tapetis</i> as Causal Agent of Disease Outbreak in Meagre (<i>Argyrosomus regius</i>)

In this work, we studied a disease outbreak that affected meagre (Argyrosomus regius) at a temperature of 14–15 °C, and that reached a mortality rate of 45% in one week. Moribund fish showed neither external nor internal signs of disease. However, a large number of bacteria, phenotypically similar and in pure culture, were recovered from the liver and kidney. A further phenotypic, genotypic and serological characterization of a selection of three isolates (a828, a834 and a842) allowed the identification of them as Vibrio tapetis. Phylogenetic analysis placed the isolates within the subspecies tapetis, being clearly differentiated from the subspecies britannicus and quintayensis. Nevertheless, all the isolates showed some phenotypic discrepancies with the type strain CECT 4600T; also, they proved to belong to a different O-serotype and genogroup (according to REP-PCR analysis) than the type strain. A virulence evaluation performed in sea bass (Dicentrarchus labrax) by intraperitoneal injection using isolate a828 in two different doses (1 × 105 and 3 × 108 cfu/fish) led to mean mortality rates of 30% and 60%, respectively, corroborating its potential to cause significant mortalities in fish. To our knowledge, this is the first evidence of pathogenic Vibrio tapetis isolates associated with disease outbreaks in meagre