Which statement best describes a bacteriostat?

• A. A substance that kills bacteria
• B. A substance that inhibits the growth or reproduction of bacteria without necessarily killing them e.g. refrigeration
• C. A substance that kills bacteria e.g. antibiotic
• D. A substance that inhibits fungal growth

Answer: (D)

Understanding how agents affect bacteria: bacteriostatic versus bactericidal actions. A bacteriostat is a substance that inhibits the growth or reproduction of bacteria without necessarily killing them. This means it slows down or stops bacterial replication, allowing the body's immune system to clear the infection. Refrigeration is a classic example because the cold slows bacterial metabolism and growth rather than killing all the bacteria outright.

In contrast, something that kills bacteria is bactericidal, removing the bacteria by destruction. An agent that kills fungi, rather than bacteria, is an antifungal and does not describe a bacteriostat. Likewise, an antibiotic that directly kills bacteria fits the bactericidal idea, not bacteriostatic.