Biotyping and serotyping of Lactococcus garvieae isolates in affected farmed rainbow trout (Oncorhynchus mykiss) in north Iran

The incidence of Lactococcosis caused by Lactococcus garvieae, in rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) farms is disquieting and increasing in recent years. Knowledge of biotypes and serotypes involved in disease incidence is essential to adopt disease prevention and control policies. Twelve isolates of L. garvieae from some rainbow trout farms were identified by phenotypic, biochemical, and molecular assays. Biotyping of the isolates was undertaken based on the acidification of carbohydrates including sucrose, tagatose, mannitol, and cyclodextrin as well as the presence of pyroglutamic acid arylamidase (Pyra) and N-acetyl-β-glucosaminidase (β-Nag) enzymes. The Serotyping classification was carried out using slide agglutination assay. The obtained results showed that all isolates were identified as biotype II. Seven isolates (58.3%) were positive for capsule formation and were classified as KG- strain and 41.7 % were classified as KG+ strains (non-capsulated strains). Further works are required for a better understanding of the diversity of Lactococcus garvieae isolates in farmed rainbow trout in Iran.