Bacteria of Enterococcus genus in milk and dairy products.

摘要

Enterococci are widely present in nature and gain entry into raw milk and milk products through equipment, unsanitary and unhygienic production and handling conditions, and through the water supply. This short review describes current knowledge on the positive and negative importance of enterococci in relation to the dairy industry. These bacteria are important for ripening and developing the aroma of certain cheeses, especially traditional cheeses produced in the Mediterranean area. Their influence on the sensory properties of cheeses seems due to specific biochemical traits such as proteolysis and lipolytic activities, citrate utilization, and production of aromatic volatile compounds. In many cheeses, enterococci occur as non-starter lactic acid bacteria (NS-LAB), and they are also components of cheese starter cultures. Some enterococci are also used as probiotics and have the ability to produce bacteriocins (enterocins) and inhibit growth of food spoilage bacteria or pathogenic bacteria. Enterococci may also reduce serum cholesterol levels, but on the other hand, can spoil milk products and cause bacteraemia or other infections. Little information is known on the virulence factors of enterococci such as adhesins, invasins and haemolysin. There is evidence that enterococci in food may produce thermostable biogenic amines provoking migraine attacks and even food poisoning. Some strains of enterococci are resistant to many antibiotics such as vancomycin. Enterococcal strains isolated from food and clinical cases have demonstrated the ability to transfer vancomycin and tetracycline resistance genes to Enterococcus sp. and other bacteria. The role of enterococci in disease and food poisoning has raised questions concerning their safety for use as probiotics in the dairy industry..