Enterococci are bacteria that live in the gastrointestinal tract (bowels) of most individuals and generally do not cause harm (this is termed “colonization”). Vancomycin-resistant enterococci (VRE) are strains of enterococci that are resistant to the antibiotic vancomycin. If a person has an infection caused by VRE, such as a urinary tract infection or blood infection, it may be more difficult to treat.

Staphylococcus Aureus is a type of bacterium that lives on the skin and mucous membranes of healthy people. Occasionally, S. Aureus can cause an infection. When S. Aureus develops resistance to certain antibiotics, it is called methicillin-resistant Staphylococcus Aureus, or MRSA.