A nosocomial infection is defined as one that is:

• A. Not contagious
• B. Resistant to antibiotics
• C. Hospital-acquired
• D. Restricted to the respiratory system

Answer: (C)

A nosocomial infection is defined by where it is acquired — in a hospital or other healthcare facility. That makes hospital-acquired the best description, because the key idea is the setting of the infection's onset, typically occurring after admission or during care in the facility. It does not depend on whether an infection can spread between people (contagiousness) or on whether the organism is resistant to antibiotics, even though many hospital infections are resistant. It also isn’t limited to infections of any particular body system; nosocomial infections can affect various sites, not just the respiratory tract. So the defining feature is the hospital origin, which is why “hospital-acquired” is the correct answer.