1. 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

2. 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.

3. 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

4. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Bacterial populations die at a constant logarithmic rate. Figure 7.1a

5. 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

6. 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

7. 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

8. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Moist heat denatures proteins boiling Autoclave e: Steam under pressure Heat Figure 7.2

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10. 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

11. 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

12. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Filtration removes microbes High-efficiencyparticuiateair(HEPA) filters remove almost all microorganisms larger than about 0.3 Micron in diameter. 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

13. 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

14. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.5

15. 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

16. 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

17. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Methods of Microbial Control Figure 7.6 Evaluating a disinfectant Disk-diffusion method

18. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Types of Disinfectants Figure 7.7 Phenol Phenolics. One of the most freque ntly used phenolics is derived fromcoal ta r, a group of chemicals called cresols. Bisphenols. 1. Hexachlorophene: used for surgical and hospital microbial control procedures. 2.Triclosan An ingredient in antibacterial soaps and at least one toothpaste. Triclosan has even been incorporated in to kitchen cutting boards and the handles of knives an d other plastic kitchenware. Disrupt plasma membranes

19. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Biguanides. Chlorhexidine Disrupt plasma membranes They are effective against gram-positive and gram- negative bacteria. Biguanides are not sporicidal but have some activity against enveloped viruses. chlorhexidine is much used for surgical hand scrubs and preoperative skin preparation in patients. Types of Disinfectants

20. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Halogens. Iodine, Chlorine Iodine active against all kinds of bacteria, many endospores, various fungi, and some viruses. Iodine impairs protein synthesis and alters cell membranes, apparently by forming complexes with amino acids and unsaturated fatty acids. Iodine is available as a tincture- that is solution in aqueous alcohol- and as an iodophor. An iodophor is a combination of iodine and an organic molecule, from which the iodine is released slowly. Types of Disinfectants

21. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Chlorine (CI 2 ), Oxidizing agents Bleach is hypochlorous acid (HOCl) used extensively for disinfecting municipal drinking water, water in swimming pools, and sewage. chloramines, combinations of chlorine and ammonia. Most municipal water-treatment systems mix ammonia with chlorine to form chloramines.

22. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Types of Disinfectants Table 7.6 Alcohols. Ethanol, isopropanol effectively kill bacteria and fungi but not endospores and nonenveloped viruses. Denature proteins, dissolve lipids. The recommended optimum concentration of ethanol is 70%, but concentrations between 60% and 95% seem to kill as well. Ethanol and isopropanol are often used to enhance the effectiveness of other chemical agents.

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24. Heavy Metals. Ag, Zn, Cu Oligodynamic action When the metal ions combine with the sulfhydryl groups on cellular proteins, Denature proteins. Silver is used as an antiseptic in a 1% silver nitrate solution. copper compounds arc effective in concentrations of one part per million of water. To prevent fungi, copper compounds such as copper 8- hydroxyquinoline are sometimes included in paint. Zinc chloride is a common ingredient in mouthwashes. Inorganic mercury compounds, such as mercuric chloride have a long history of use as disinfectants. Types of Disinfectants

25. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Surface-Active Agents or Surfactants can decrease surface tension among molecules of a liquid. Types of Disinfectants SoapDegerming Acid-anionic detergentsSanitizing negative charge Quarternary ammonium compounds Cationic detergents Bactericidal, Denature proteins, disrupt plasma membrane, positive charge. fungicidal,amoebicidal, and virucidal against enveloped viruses. They do not kill endospores or mycobacteria.

26. 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

27. 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 Formaldehyde gas is an excellent disinfectant. However, it is more commonly available as formalin, a 37% aqueous solution of formaldehyde gas. Glutaraldehyde is a chemical relative of formaldehyde that is less irritating and more effective than formaldehyde. Glutaraldehyde is used to disinfect hospital instruments, Types of Disinfectants

28. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Gaseous Sterilants Denature proteins Ethylene oxide kills all microbes and endospores but requires a lengthy exposure period of several hours. It is toxic and explosive in its pure form, so it is usually mixed with a nonflammable gas, such as carbon dioxide. Types of Disinfectants

29. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Peroxygens are a group of oxidizing agents that includes hydrogen peroxide and peracetic acid. O 3, H 2 O 2, peracetic acid Hydrogen peroxide is an antiseptic found in many household medicine cabinets and in hospital supply rooms. Heated hydrogen peroxide can be used as a gaseous sterilant. Types of Disinfectants

30. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Microbial Characteristics and Microbial Control Figure 7.11 Gram-negative bacteria are generally more resistant than gram- positive bacteria to disinfectants and antiseptics. 2. Mycobacteria, endospores, and protozoan cysts and oocysts are very resistant to disinfectants and antiseptics. 3. Nonenveloped viruses are generally more resistant than enveloped viruses to disinfectants and antiseptics. 4. Prions are resistant to disinfection and autodaving.

31. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Microbial Characteristics and Microbial Control Chemical agentEffectiveness against EndosporesMycobacteria PhenolicsPoorGood QuatsNone ChlorinesFair AlcoholsPoorGood GlutaraldehydeFairGood