Which trait is commonly used to isolate staphylococci from clinical specimens?

• A. Bile resistance
• B. Growth at 55°C
• C. High salt tolerance
• D. Resistance to novobiocin

Answer: (C)

High salt tolerance. Staphylococci can grow in very salty environments, so selective media with high NaCl like Mannitol Salt Agar inhibits most other bacteria and allows Staphylococcus species to be isolated from mixed clinical specimens. This salt-based selection is the primary reason the trait is used for isolation.

Other options aren’t used for isolation because they’re not general traits that distinguish Staphylococcus from remaining bacteria in a specimen: bile resistance points to enterococci and related organisms, growth at 55°C targets different groups of bacteria, and novobiocin resistance is mainly useful for differentiating a specific Staphylococcus species (like S. saprophyticus) rather than for broad isolation.