Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture Slide Presentation prepared by Christine L. Case Microbiology B.E Pruitt & Jane J. Stein AN INTRODUCTION EIGHTH EDITION TORTORA FUNKE CASE Chapter 7 The Control of Microbial Growth
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The Control of Microbial Growth Sepsis refers to microbial contamination. Asepsis is the absence of significant contamination. Aseptic surgery techniques prevent microbial contamination of wounds.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Sterilization: Removal of all microbial life Commercial Sterilization: Killing C. botulinum endospores Disinfection: Removal of pathogens Antisepsis: Removal of pathogens from living tissue Degerming: Removal of microbes from a limited area Sanitization: Lower microbial counts on eating utensils Biocide/Germicide: Kills microbes Bacteriostasis: Inhibiting, not killing, microbes Terminology
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Bacterial populations die at a constant logarithmic rate. Figure 7.1a
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Number of microbes Environment (organic matter, temperature, biofilms) Time of exposure Microbial characteristics Effectiveness of antimicrobial treatment depends on: Figure 7.1b
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Alternation of membrane permeability Damage to proteins Damage to nucleic acids Actions of Microbial Control Agents
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heat Thermal death point (TDP): Lowest temperature at which all cells in a culture are killed in 10 min. Thermal death time (TDT): Time to kill all cells in a culture Decimal reduction time (DRT): Minutes to kill 90% of a population at a given temperature Physical Methods of Microbial Control
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Moist heat denatures proteins Autoclave: Steam under pressure Heat Figure 7.2
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Pasteurization reduces spoilage organisms and pathogens Equivalent treatments 63°C for 30 min High-temperature short-time 72°C for 15 sec Ultra-high-temperature: 140°C for <1 sec Thermoduric organisms survive Physical Methods of Microbial Control
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Dry Heat Sterilization kills by oxidation Flaming Incineration Hot-air sterilization Physical Methods of Microbial Control Hot-airAutoclave Equivalent treatments170˚C, 2 hr121˚C, 15 min
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Filtration removes microbes Low temperature inhibits microbial growth Refrigeration Deep freezing Lyophilization High pressure denatures proteins Desiccation prevents metabolism Osmotic pressure causes plasmolysis Physical Methods of Microbial Control
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Radiation damages DNA Ionizing radiation (X rays, gamma rays, electron beams) Nonionizing radiation (UV) (Microwaves kill by heat; not especially antimicrobial) Physical Methods of Microbial Control
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.5
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Principles of effective disinfection Concentration of disinfectant Organic matter pH Time Chemical Methods of Microbial Control
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Evaluating a disinfectant Use-dilution test 1. Metal rings dipped in test bacteria are dried 2. Dried cultures placed in disinfectant for 10 min at 20°C 3. Rings transferred to culture media to determine whether bacteria survived treatment Chemical Methods of Microbial Control
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Methods of Microbial Control Figure 7.6 Evaluating a disinfectant Disk-diffusion method
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Types of Disinfectants Figure 7.7 Phenol Phenolics. Lysol Bisphenols. Hexachlorophene, Triclosan Disrupt plasma membranes
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Biguanides. Chlorhexidine Disrupt plasma membranes Types of Disinfectants
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Halogens. Iodine, Chlorine Oxidizing agents Bleach is hypochlorous acid (HOCl) Types of Disinfectants
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Types of Disinfectants Table 7.6 Alcohols. Ethanol, isopropanol Denature proteins, dissolve lipids
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heavy Metals. Ag, Hg, Cu Oligodynamic action Denature proteins Types of Disinfectants
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Surface-Active Agents or Surfactants Types of Disinfectants SoapDegerming Acid-anionic detergentsSanitizing Quarternary ammonium compounds Cationic detergents Bactericidal, Denature proteins, disrupt plasma membrane
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Food Preservatives Organic Acids Inhibit metabolism Sorbic acid, benzoic acid, calcium propionate Control molds and bacteria in foods and cosmetics Nitrite prevents endospore germination Antibiotics. Nisin and natamycin prevent spoilage of cheese Types of Disinfectants
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Aldehydes Inactivate proteins by cross-linking with functional groups (–NH 2, –OH, –COOH, —SH) Glutaraldehyde, formaldehyde Types of Disinfectants
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Gaseous Sterilants Denature proteins Ethylene oxide Types of Disinfectants
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Peroxygens Oxidizing agents O 3, H 2 O 2, peracetic acid Types of Disinfectants
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Microbial Characteristics and Microbial Control Figure 7.11
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Microbial Characteristics and Microbial Control Chemical agentEffectiveness against EndosporesMycobacteria PhenolicsPoorGood QuatsNone ChlorinesFair AlcoholsPoorGood GlutaraldehydeFairGood