Recently we discussed the environmental factors that promote the growth of microbes; and we have also studied the primary methods of spreading or transmitting microbes. Now we need to turn our attention to selecting agents and activities used to control microbial growth and also understanding the variety and method of action of selected controls.

Early scientists like Aristotle in 300 B.C. recognized the importance of burying feces and boiling water to reduce the spread of disease and sickness. Even prehistoric humans dried food like fish to reduce spoiling. If E. coli could produce a mass of organisms greater than the mass of the earth in less than 48 hours under optimal growth condition, we must understand that the control of microbes is necessary and know that it is absurd to think E. coli could grow to such numbers without first running out of food or producing poisons that would inhibit its growth. Many relatively recent accounts of the spread of hepatitis-B from acupuncture using contaminated needles have reminded us of the present need to control microbes. From the early burning of clothing of plague victims, burning sulfur to fumigate houses, anointing bodies with ointments and oils, and exposing bedding to sunlight, people have become more knowledgeable in understanding how to control microbes.

Eliminating the source by treating or isolating the infected and minimizing the transmission of the microbe which causes the disease by treating water, watching food, and destroying vectors along with immunization programs have led to the reduction of several infectious diseases. It is impossible, and probably unwise, to try to eliminate all microbes from the environment; but we must daily practice activities that prevent the spread of disease-causing microbes, reduce spoilage, and keep food and water safe for us to use.

What is the definition of control? In this unit of microbiology, control means any agent or substance as well as action that reduces, inhibits, or eliminates microbes.