CONTROL OF MICROORGANISMS PRINCIPLES OF MICROBIAL CONTROL CH. 7 & 20 QUESTIONS & ANSWERS Factors influencing success of control methods: Number & nature of microorganisms: - ANS-Gram-negative bacteria are generally more resistant than gram-positive bacteria to disinfectants & antiseptics. Mycobacteria, endospores, & protozoan cysts & oocyst are very resistant to disinfectants & antiseptics. Nonenveloped viruses are generally more resistant than enveloped viruses to disinfectants & antiseptics. Prions are resistant to disenfections & autoclaving. Factors influencing success of control methods: Strength & control agent - ANS-The plasma membrane of a mocroorganism located inside the cell wall is the target for microbial control agent. Damage to the lipids or proteins of the plasma membrane by antimicrobial agents causes cellular contents to leak & interfers with the growth of the cell. The nucleic acids DNA & RNA carry the cells genetic information. Damage to the nucleic acid by heat radiation, or chemicals is frequently lethal to the cell. The cell can't replicate or carry out normal metabolic functions like the synthesis of enzymes. Time, temp, & pH: - ANS-Temp: Heat kills microorganisms by denaturing their enzymes; changing the 3-dimensional shapes of these proteins inactivates them. Increase the temp by 10C doubles the rate of chemical reactions & increase the potency of the chemical agent. Time: Chemical antimicrobials often require extended exposure to more-resistant microbes or endospores. pH: Acidic or alkaline pH can increase or decrease the agent's potency. A pH that increases the degree of ionization of chemical agent often increase its ability to penetrate a cell. General methods of control: Bactericidal vs. bacteriostatic - ANS-Bacteriostatic are growth interfering by: 1. bacteria protein production. 2. bacteria DNA production. 3. bacteria cellular metabolism. Bactericidal will prevent or inhibit the growth of microbes. High concentration may be bactericidal & low concentration bacteriostatic. CONTINUES...
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