1Chapter 7Control of Microorganisms by Physical and Chemical Agents2Definition of Frequently Used Terms• sterilization– destruction or removal of all viable organisms• disinfection– killing, inhibition, or removal of pathogenic organisms – disinfectants• agents, usually chemical, used for disinfection• usually used on inanimate objects3More definitions…• sanitization– reduction of microbial population to levels deemed safe (based on public health standards)• antisepsis– prevention of infection of living tissue by microorganisms–antiseptics• chemical agents that kill or inhibit growth of microorganisms when applied to tissue4Antimicrobial agents• agents that kill microorganisms or inhibit their growth• -cidal agents kill• -static agents inhibit growth5-cidal agents-cide– suffix indicating that agent kills• germicide– kills pathogens and many nonpathogens but not necessarily endospores• include bactericides, fungicides, algicides, and viricides6-static agents-static– suffix indicating that agent inhibits growth– include bacteriostatic and fungistatic7The Pattern of Microbial Death• microorganisms are not killed instantly• population death usually occurs exponentially• microorganisms are considered to be dead when they are unable to reproduce in conditions that normally support their reproduction8Conditions Influencing the Effectiveness of Antimicrobial Agent Activity• population size– larger populations take longer to kill than smaller populations• population composition– microorganisms differ markedly in their sensitivity to antimicrobial agents9More conditions…• concentration or intensity of an antimicrobial agent– usually higher concentrations or intensities kill more rapidly– relationship is not linear• duration of exposurelonger exposure ⇒ more organisms killed10More conditions…• temperature– higher temperatures usually increase amount of killing• local environment– many factors (e.g., pH, viscosity and concentration of organic matter) can profoundly impact
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