Enterococci: yin - yang microbes

This review deals with the duality of enterococci, which can be illustrated by their yin - yang behaviour. The rough nature of this specific group of lactic acid bacteria promotes their dissemination in various environments where they significantly influence the outcome of a certain process. In the technological meaning, enterococci are leading microbes in fermentation processes of traditional foods, where their detrimental spoilage activities are equally significant. As therapeutics, enterococci manifest the probiotic properties through their positive effects on maintaining of the normal intestinal microflora, on stimulation of the immune system, on improved nutritional value of food and with the production of antimicrobial compounds (bacteriocins). At the same time, enterococci present an emerging pool of opportunistic pathogens for humans as they cause disease, possess agents for antibiotic resistance and their transfer mechanisms, and are frequently armed with potential virulence factors. Despite the yin - yang characteristics of enterococci, the long history of safe use of certain strains of enterococci in food/feed, and reliable identification and classification of enterococci with phenotypic methods supported with modern genetic tools, enables selection of promising enterococci, which could be safely used as starter cultures or food/feed additives.