Incorporation of Propionibacteria in Fermented Milks as a Probiotic.

Propionibacteria are mainly found in dairy products and fermented milks but are found in other foods as well. Dairy propionibacteria have recently shown to exert potential probiotic activities such as production of propionic acid, vitamins, bacteriocins, essential enzymes, and other vital metabolites. Furthermore, stimulating the immune system and lowering the blood cholesterol level are some of their favorable effects. They have a wide spectrum of antimicrobial activities, inhibiting the growth of gram-positive and some gram-negative bacteria, as well as some yeasts and molds. At industrial scale, they are used in cheese making, especially Swiss (hard) cheeses, as dominant starter cultures. There is a rising trend to use propionibacteria in fermented milks as probiotic. The current paper reviews the characteristics of propionibacteria related to their use in fermented milks either as starter culture or probiotic, methods for the enumeration of propionibacteria, and their functional (in vivo) efficiency.

Bacteriophage-mediated transduction of antibiotic resistance in enterococci.

AIMS: Temperate bacteriophages are bacterial viruses that transfer genetic information between bacteria. This phenomenon is known as transduction, and it is important in acquisition of bacterial virulence genes and antimicrobial resistance determinants. The aim of this study was to demonstrate the role of bacteriophages in gene transfer (antibiotic resistance) in enterococci. METHODS AND RESULTS: Three bacteriophages from environmental samples isolated on pig host strains of Enterococcus gallinarum and Enterococcus faecalis were evaluated in transduction experiments. Antibiotic resistance was transferred from Ent. gallinarum to Ent. faecalis (tetracycline resistance) and from Ent. faecalis to Enterococcus faecium, Enterococcus hirae/durans and Enterococcus casseliflavus (gentamicin resistance). CONCLUSIONS: Bacteriophages play a role in transfer of antibiotic resistance determinants in enterococci. SIGNIFICANCE AND IMPACT OF THE STUDY: This study confirms previous suggestions on transduction in enterococci, in particular on interspecies transduction. Interspecies transduction is significant because it widens the range of recipients involved in antimicrobial resistance transfer.