Which term refers to bacteria that are harmless and beneficial to humans?

• A. Pathogenic Bacteria
• B. Saprophytes
• C. Nonpathogenic Bacteria
• D. Measles

Answer: (C)

Nonpathogenic bacteria are those that do not cause disease and can even support health. These harmless bacteria live on our skin, in our gut, and elsewhere, helping with digestion, producing vitamins, and protecting against harmful microbes by competitive exclusion. Saprophytes describe organisms that decompose dead organic matter and aren’t defined by their direct relationship to human health, so they don’t specifically denote beneficial bacteria in humans. Measles is caused by a virus, not bacteria, so it isn’t relevant to the question.