Microbiology 6e

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Chapters 8 and 9 Sterilization, Growth and
Antimicrobial Therapy
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Chapter 12 Sterilization and Disinfection
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D E F I N I T I O N S 1
Antimicrobial Agents
Disinfectant
Antiseptic
Antibiotic
Inanimate Objects
External Tissues
Internal Tissues
e.g. Ethanol
e.g. Ampicillin
e.g. Bleach
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D
E F I N I T I O N S 2

• Sterilization Killing or removal of ALL
  microbes
• Disinfection Reducing the number of microbes
• Bactericidal killing bacteria
• Bacteriostatic growth inhibiting

Microbes differ in their susceptibility to
antimicrobial agents.
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The Potency of Chemical Agents 1
Time Temperature pH Concentration
Potency (Effectiveness)
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The Potency of Chemical Agents 2
Reference
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The Potency of Chemical Agents 3
The Filter Paper Method
Staphylococcus aureus Gram ()
Escherichia coli Gram (-)
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Mechanisms of Action of Antimicrobial Agents
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Denaturation of Proteins by Heat
(Autoclaving)
Irreversible
Reversible
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Denaturation of Proteins by Chemicals
Acids, alkali hydrolyze peptide bonds
Peroxides, permanganates oxidize S-S- and -SH
Halogens (Br, Cl, F, I) exchange H in COOH,
-NH2, -OH groups of proteins
Heavy Metals (copper, mercury, silver) attach to
SH groups
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Surfactant Action on Membrane Lipids
Surfactants alcohols, soaps, detergents,
Action of soap
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UV Light
UV
- UV
Serratia marcescens
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Membrane Filters
Staphylococcus on 0.22 ?m filter
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Chapters 8 and 9 Sterilization, Growth and
Antimicrobial Therapy
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Spectrum of Antibiotic Activity
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Modes of Antibiotic Action
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Inhibition of cell wall synthesis by penicillin
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- antibiotic
antibiotic
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Effects of premature termination of antibiotic
treatment
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Side Effects
Toxicity (e.g. damage to liver, teeth,
etc.) Allergies Killing of normal flora
Mitochondria resemble bacteria.