Genetic analysis of human clinical isolates of Lactococcus garvieae: Relatedness with isolates from foods

Abstract

Lactococcus garvieae is a Gram-positive bacterium well-known as an important pathogen in aquaculture, and it is also a human pathogen of increasing clinical significance. Forty-three human L. garvieae isolates from clinical specimens were characterized by Multilocus Sequence Typing (MLST). Twenty-six different sequence types (STs) were identified among the human isolates, of which 20 were novel STs. Most human isolates clustered into four clonal complexes, with a predominance of CC3. Within CC3, ST10 was the most common genotype, indicating the existence of a circulating genetic lineage among the human isolates analyzed. The four CCs also grouped L. garvieae strains isolated from meat, dairy and fish, indicating a genetic overlap between isolates from human and these foods. Genetic relatedness among human and food L. garvieae isolates was confirmed by phylogenetic analysis based on the concatenated sequences of the seven MLST genes. These results represent the first evidence of genetic relatedness between isolates of L. garvieae of human and those isolated meat, milk and dairy products and suggest that, in addition to fish and seafood, these foods might represent important sources of human L. garvieae infections.

Keywords: Food; Human; L. garvieae; MLST.