17.1: Introduction

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A. INTRODUCTION TO THE CONTROL OF MICROORGANISMS

The next two labs deal with the inhibition, destruction, and removal of microorganisms. Control of microorganisms is essential in order to prevent the transmission of diseases and infection, stop decomposition and spoilage, and prevent unwanted microbial contamination.

Microorganisms are controlled by means of physical agents and chemical agents. Physical agents include such methods of control as high or low temperature, desiccation, osmotic pressure, radiation, and filtration. Control by chemical agents refers to the use of disinfectants, antiseptics, antibiotics, and chemotherapeutic antimicrobial chemicals.

Basic terms used in discussing the control of microorganisms include:

1. Sterilization
Sterilization is the process of destroying all living organisms and viruses. A sterile object is one free of all life forms, including bacterial endospores, as well as viruses.

2. Disinfection
Disinfection is the elimination of microorganisms, but not necessarily endospores, from inanimate objects or surfaces.

3. Decontamination
Decontamination is the treatment of an object or inanimate surface to make it safe to handle.

4. Disinfectant
A disinfectant is an agents used to disinfect inanimate objects but generally to toxic to use on human tissues.

5. Antiseptic
An antiseptic is an agent that kills or inhibits growth of microbes but is safe to use on human tissue.

6. Sanitizer
A sanitizer is an agent that reduces, but may not eliminate, microbial numbers to a safe level.

7. Antibiotic
An antibiotic is a metabolic product produced by one microorganism that inhibits or kills other microorganisms.

8. Chemotherapeutic antimicrobial chemical
Chemotherapeutic antimicrobial chemicals are synthetic chemicals that can be used therapeutically.

9. Cidal
An agent that is cidal in action will kill microorganisms and viruses.

10. Static
An agent that is static in action will inhibit the growth of microorganisms.

These two labs will demonstrate the control of microorganisms with physical agents, disinfectants and antiseptics, and antimicrobial chemotherapeutic agents. Keep in mind that when evaluating or choosing a method of controlling microorganisms, you must consider the following factors which may influence antimicrobial activity:

1. the concentration and kind of a chemical agent used;

2. the intensity and nature of a physical agent used;

3. the length of exposure to the agent;

4. the temperature at which the agent is used;

5. the number of microorganisms present;

6. the organism itself; and

7. the nature of the material bearing the microorganism.

Contributors and Attributions

Dr. Gary Kaiser (COMMUNITY COLLEGE OF BALTIMORE COUNTY, CATONSVILLE CAMPUS)