P2.8.1^8.1. Definitions of Frequently Used Terms^192^193^,,^6700^6747%
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8.1
Definitions of Frequently Used Terms

Terminology is especially important when the control of microorganisms is discussed because words such as disinfectant and antiseptic often are used loosely. The situation is even more confusing because a particular treatment can either inhibit growth or kill, depending on the conditions. The types of control agents and their uses are outlined in figure 8.1. In general, to control microorganisms a biocide must be evaluated so as to determine the specific parameters under which it is to be effective.

 
FIGURE 8.1
Microbial Control Methods.
Figure 8.1 Micro Inquiry

Which types of agents can be used for sterilization? Which can be used for antisepsis? What is the difference?

Sterilization (Latin sterilis, unable to produce offspring or barren) is the process by which all living cells, spores, and acellular entities (e.g., viruses, viroids, virusoids, and prions) are either destroyed or removed from an object or habitat. A sterile object is totally free of viable microorganisms, spores, and other infectious agents. When sterilization is achieved by a chemical agent, the chemical is called a sterilant. In contrast, disinfection is the killing, inhibition, or removal of microorganisms that may cause disease; disinfection is the substantial reduction of the total microbial population and the destruction of potential pathogens. Disinfectants are agents, usually chemical, used to carry out disinfection and normally used only on inanimate objects. A disinfectant does not necessarily sterilize an object because viable spores and a few microorganisms may remain. Sanitization is closely related to disinfection. In sanitization, the microbial population is reduced to levels that are considered safe by public health standards. The inanimate object is usually cleaned as well as partially disinfected. For example, sanitizers are used to clean eating utensils in restaurants. Viroids and virusoids (section 5.6); Prions (section 5.7)

It also is frequently necessary to control microorganisms on or in living tissue with chemical agents. Antisepsis (Greek anti, against, and sepsis, putrefaction) is the destruction or inhibition of microorganisms on a living tissue; it is the prevention of infection or sepsis. Antiseptics are chemical agents applied to tissue to prevent infection by killing or inhibiting pathogen growth; they also reduce the total microbial population. Because they must not destroy too much host tissue, antiseptics are generally not as toxic as disinfectants. The exposure of microorganisms to increasing biocide concentrations decreases the number of viable organisms. Figure 8.2 shows three possible population reduction curves resulting from three different biocides. The shape of the curve reflects various conditions that influence biocide effectiveness. Note that in each case, the eventual decline in viable microorganisms can occur as a staged decline of viability from antisepsis to sterilization. Chemotherapy is the use of chemical agents to kill or inhibit the growth of microorganisms within host tissue. Antimicrobial chemotherapy (chapter 34)

 
FIGURE 8.2
Impact of Biocide Exposure.Three exponential plots of survivors versus time of biocide exposure, indicating the potential kinetics of biocide action. Note how the general terms referencing microbial control are reflected by decreasing numbers of microbes. For example, sterilization refers to the absence of viable organisms regardless of biocide kinetics.

A suffix can be employed to denote the type of antimicrobial agent. Substances that kill organisms often have the suffix –cide (Latin cida, to kill); a cidal agent kills pathogens (and many nonpathogens) but not necessarily endospores. A disinfectant or antiseptic can be particularly effective against a specific group, in which case it may be called a bactericide, fungicide, or viricide. Other chemicals do not kill but rather prevent growth. If these agents are removed, growth will resume. Their names end in –static (Greek statikos, causing to stand or stopping)—for example, bacteriostatic and fungistatic.

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  1. Define the following terms: sterilization, sterilant, disinfection, disinfectant, sanitization, antisepsis, antiseptic, chemotherapy, biocide.

  2. What is the difference between bactericidal and bacteriostatic? To which category do you think most household cleaners belong? Why?