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 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
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Sanitization: Lower microbial counts on eating utensils Biocide/Germicide: Kills microbes Bacteriostasis: Inhibiting, not killing, microbes Sepsis refers to microbial contamination. Asepsis is the absence of significant contamination. Aseptic surgery techniques prevent microbial contamination of wounds. 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, biofilms) Time of exposure Microbial characteristics Temperture. cioncentration 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 ( enzymes) 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 liquid culture are killed in 10 min. Thermal death time (TDT): the minimal length of Time to kill all cells in a liquid culture at a given temp. Decimal reduction time (DRT): times in 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 Boiling 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 (HTST) 72°C for 15 sec Ultra-high-temperature (UTH): 140°C for <1 sec Equivalent treatment. 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 1.Heat sensitive material 2.High efficiency particulate air filters 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) Wavelength less than 1 nm, Ionizing water Short wave length, much more energy. Nonionizing radiation (UV) (260nm) (Microwaves kill by heat; not especially antimicrobial) Microwaves 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 Phenol coefficient test 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 Lipid in Cell membrane Phenolics. Cresol ( Lysol) Bisphenols. Hexachlorophene,lotion Triclosan in kitchenware
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Biguanides. Chlorhexidine Disrupt plasma membranes Mycobacterium relatively resist Endospores and cyst not affected Enveloped viruses and most vegetative cell affected Types of Disinfectants
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Halogens. Iodine, Chlorine Iodine combined with AA in enzymes and protein Present as iodophore as povidone iodines or tincture Chlorine Bleach is hypochlorous acid (HOCl) Its strong oxidizing agent Used in water disinfectant Can present in many form as calcium hypochlorite, sodium hypochlorite, chloramines. 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 Not effect on spores or nonenveloped viruses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heavy Metals. Ag, Hg, Cu Oligodynamic action Denature proteins Silver nitrate 1% used as antiseptic eye drops. Cupper sulfate used to destroy green algae Zinc chloride used as a mouth washing. 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 Potassium sorbate and sodium benzoate prevent spolige of acidic food. Calcium propionate prevent growth of bacillus spores in bread. Nitrite prevents endospore germination. Types of Disinfectants
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Antibiotics. Nisin prevent endospore growth is an example of bacteriocin. natamycin antifungal prevent spoilage of cheese Aldehydes Inactivate proteins by cross-linking with functional groups (–NH 2, –OH, –COOH, —SH) Formaldehyde present in form of 37% aqueous solution Glutaraldehyde, as 2% is bactericidal, tuberculocidal, virucidal in 10 min and sporocidal hours. Types of Disinfectants
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Gaseous Sterilants Denature proteins Ethylene oxide Widely used in medical supplies. Disadvantage they are suspected cacinogenes Types of Disinfectants
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Peroxygens Oxidizing agents O 3,used in stead of chlorine in water. H 2 O 2, peracetic acid is sporocidal effect on endospore and viruses within 30 min and kill vegetative within 5 min. 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