Effect of Raw-Milk Cheese Consumption on the Enterococcal Flora of Human Feces

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Abstract
Enterococci are one of the major facultative anaerobic bacterial groups that reside in the human gastrointestinal tract. In the present study, the composition of the enterococcal fecal flora in three healthy humans was analyzed before, during, and after the daily consumption of ∼125 g of a raw-milk Cheddar-type cheese containing 3.2 × 10 4 enterococci/g of cheese. Enterococcal counts ranged between 1.4 × 10 2 and 2.5 × 10 8 CFU/g of feces and differed from subject to subject and from week to week. The cheese contained mainly Enterococcus casseliflavus and a small population of Enterococcus faecalis . Clonal relationships were determined by pulsed-field gel electrophoresis. Before and after consumption of the cheese, samples from humans contained mainly Enterococcus faecium , with some of the clones being resident. During consumption of the cheese, one particular transient clone of E. faecalis , clone Fs2, which was present in small numbers in the cheese, largely dominated the feces. Two clones of E. casseliflavus from the cheese were also found in the feces of one of the subjects during cheese consumption. These results suggest that a clone need not be present in a food in high numbers to establish itself in the intestine.