The salt tolerance test (6.5% salt broth) is primarily used to identify which organism?

The salt tolerance test, specifically the 6.5% salt broth test, is utilized to identify Enterococcus faecalis due to its ability to thrive in high-salt environments. Enterococci, particularly Enterococcus faecalis, are known for their hardy nature and can grow in the presence of elevated sodium concentrations that would inhibit the growth of many other bacteria.

In clinical settings, this characteristic is significant for distinguishing Enterococcus faecalis from other streptococcal species that do not exhibit the same level of salt tolerance. For example, Streptococcus pneumoniae, which is not typically found in environments with high salt concentrations, would fail to grow in such conditions. Similarly, Streptococcus bovis and Streptococcus equinus are typically less tolerant to the high salt concentrations present in the test, making them poor candidates for growth in 6.5% salt broth.

The ability of Enterococcus faecalis to endure such osmotic stress highlights its resilience and adaptability, which are important factors in its role as a pathogen and its contributions to human infections, particularly in immunocompromised patients. Thus, the salt tolerance test serves as a reliable method for identifying Enterococcus faecalis in clinical microbiology.