How would you define an antibiotic?

An antibiotic is defined as a chemical secreted by a living organism that kills or reduces the reproduction of other organisms. This definition captures the essential characteristic of antibiotics — they are typically produced by microorganisms, such as fungi and bacteria, to inhibit the growth of or kill competing microorganisms. This natural origin is key, as many antibiotics were originally discovered from natural sources.

The definition emphasizes not just the ability to kill but also the capacity to inhibit reproduction, which is vital in distinguishing antibiotics from other antimicrobial agents. While some compounds can inhibit bacterial growth, this can sometimes be a temporary effect rather than a lethal one. The ability of antibiotics to either kill pathogens or suppress their reproduction is crucial for treating infections effectively.

Other definitions provided in the choices fall short of covering the full nature of antibiotics. For example, a definition limiting them to only inhibiting bacterial growth does not account for their diverse effects against other microorganisms. Similarly, suggesting that they are synthetic compounds ignores the fact that many antibiotics are derived from natural sources. Lastly, a definition that claims antibiotics promote bacterial growth directly contradicts their primary function in combating infections. Thus, the selected definition captures the essence of what defines an antibiotic in microbiological and medical contexts.