Genetic investigation within Lactococcus garvieae revealed two genomic lineages

The diversity of a collection of 49 Lactococcus garvieae strains, including isolates of dairy, fish, meat, vegetable and cereal origin, was explored using a molecular polyphasic approach comprising PCR-ribotyping, REP and RAPD-PCR analyses and a multilocus restriction typing (MLRT) carried out on six partial genes (atpA, tuf, dltA, als, gapC, and galP). This approach allowed high-resolution cluster analysis in which two major groups were distinguishable: one group included dairy isolates, the other group meat isolates. Unexpectedly, of the 12 strains coming from fish, four grouped with dairy isolates, whereas the others with meat isolates. Likewise, strains isolated from vegetables allocated between the two main groups. These findings revealed high variability within the species at both gene and genome levels. The observed genetic heterogeneity among L. garvieae strains was not entirely coherent with the ecological niche of origin of the strains, but rather supports the idea of an early separation of L. garvieae population into two independent genomic lineages. Introduction In the last two decades, foodborne diseases have been emerging as an important and growing public health concern. Among the causes, changes in agricultural and zootechnical practices, increase in international trade, changes in consumer lifestyles, and increasing number of old and/or immune-compromised consumers have been mentioned. Furthermore, new pathogens or new biovars of known bacterial species are frequently being reported (Mor-Mur & Yuste, 2010). The impact of most new pathogens on specific ecosystems and their pathogenicity are not known. Indeed, the traditional food inspection systems are insufficient, because knowledge of the emerging pathogens is incomplete. Furthermore, the new techniques based on DNA analysis are not always applicable, in the absence of genetic data on these new biotypes. Therefore, to determine the concept of healthy food, it is crucially important that we expend efforts to comprehensive study of new emerging pathogens present in food products.