Which reaction indicates a presumptive identification of Enterococcus faecalis?

The presumptive identification of Enterococcus faecalis is indicated by the ability of the organism to grow in 6.5% salt, which tests for its tolerance to increased sodium chloride concentrations. Enterococcus faecalis is known for its high salinity tolerance, which is a key characteristic that helps differentiate it from other enterococci and related genera that may not thrive in such conditions. This characteristic is part of its identification profile since many other bacteria cannot grow in high salt concentrations.

In contrast, the other reactions listed serve to differentiate Enterococcus from other species or groups but do not serve as definitive criteria for Enterococcus faecalis. For example, the PYR test, which indicates the ability to hydrolyze L-pyrrolidonyl-β-naphthylamide, can be positive for many beta-hemolytic streptococci, not exclusively Enterococcus. Bile solubility is mainly related to the classification of Streptococcus pneumoniae, and while Enterococcus can show varied responses in hydrolysis, hippurate hydrolysis is not a characteristic test for Enterococcus faecalis specifically.