An antimicrobial agent is an agent that kills microorganisms or inhibits their growth. The efficiency of antimicrobial agents is important to the destruction of microorganisms and inhibition of microbial growth. These factors affect the efficiency of antimicrobial agents.
- Population size of micrroorganisms (m.o). A larger population needs a longer time to die than a smaller one.
- Population Composition. The effectiveness of an agent varies greatly with the nature of the organisms being teated becacuse microorganisms differ markedly in susceptibility. Bacterial endospores are much more resistant to most antimicrobial agents than are vegetative forms, and youner cells are usually more readily destroyed than mature organisms.
- Concentration of antimicrobial agents. Often but not always, the more concetrated a chemical agent or intense a physical agent, the more rapidly m.o are destroyed. However, agent effectiveness usually is not directly related to concentration. Over a short range a small increase in concentration leads to an exponential rise in effectiveness; beyond a certain point, increases may not raise the killing rate much at all. Sometimes an agent is more effective at lower concentrations. For instance, 70% ethanol is more effective than 95% because its activity is enhanced by presence of water.
- Duration of exposure. The longer a population is exposed to a microbial agent, the more organisms are killed.
- Temperature. An increase in the temperature at which a chemical acts often enhances its activity. Frequently a lower concentration od disinfectant or sterilizing agent can be used at a higher temperature.
- Local environment. This is related to environment factors such as pH, organic matter that can protect m.o, etc.