1. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint ® Lecture Slide Presentation prepared by Christine L. Case M I C R O B I O L O G Y a n i n t r o d u c t i o n ninth edition TORTORA  FUNKE  CASE 7 The Control of Microbial Growth

2. Copyright © 2006 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 © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Terminology  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

4. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Bacterial populations die at a constant logarithmic rate. Figure 7.1a

5. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Effectiveness of Antimicrobial Treatment  Depends on:  Number of microbes  Environment (organic matter, temperature, biofilms)  Time of exposure  Microbial characteristics Figure 7.1b

6. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Actions of Microbial Control Agents  Alternation of membrane permeability  Damage to proteins  Damage to nucleic acids

7. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Physical Methods of Microbial Control  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

8. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Decimal Reduction Time (DRT)  Minutes to kill 90% of a population at a given temperature Table 7.2

9. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Heat  Moist heat denatures proteins  Autoclave: Steam under pressure Figure 7.2

10. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.3 Steam Sterilization  Steam must contact item’s surface.

11. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Physical Methods of Microbial Control  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

12. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hot-airAutoclave Equivalent treatments170˚C, 2 hr121˚C, 15 min Physical Methods of Microbial Control  Dry heat sterilization kills by oxidation  Flaming  Incineration  Hot-air sterilization

13. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Physical Methods of Microbial Control  Filtration removes microbes  Low temperature inhibits microbial growth  Refrigeration  Deep freezing  Lyophilization  High pressure denatures proteins  Desiccation prevents metabolism  Osmotic pressure causes plasmolysis

14. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Physical Methods of Microbial Control  Radiation damages DNA  Ionizing radiation (X rays, gamma rays, electron beams)  Nonionizing radiation (UV)  (Microwaves kill by heat; not especially antimicrobial)

15. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.5

16. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Methods of Microbial Control  Principles of effective disinfection  Concentration of disinfectant  Organic matter  pH  Time

17. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Methods of Microbial Control  Evaluating a disinfectant  Use-dilution test 1.Metal rings dipped in test bacteria are dried. 2.Dried cultures are placed in disinfectant for 10 min at 20°C. 3.Rings are transferred to culture media to determine whether bacteria survived treatment.

18. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Methods of Microbial Control  Evaluating a disinfectant  Disk-diffusion method Figure 7.6

19. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Disinfectants  Phenol  Phenolics: Lysol  Bisphenols: Hexacholorphene, Triclosan  Disrupt plasma membranes Figure 7.7

20. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Disinfectants  Biguanides: Chlorhexidine  Disrupt plasma membranes

21. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Disinfectants  Halogens: Iodine, chlorine  Oxidizing agents  Bleach is hypochlorous acid (HOCl)

22. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Disinfectants  Alcohols: Ethanol, isopropanol  Denature proteins, dissolve lipids Table 7.6

23. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Disinfectants  Heavy metals: Ag, Hg, and Cu  Oligodynamic action  Denature proteins

24. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings SoapDegerming Acid-anionic detergentsSanitizing Quarternary ammonium compounds Cationic detergents Bactericidal, Denature proteins, disrupt plasma membrane Types of Disinfectants  Surface-active agents or surfactants

25. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Disinfectants  Chemical food preservatives  Organic acids  Inhibit metabolism  Sorbic acid, benzoic acid, and calcium propionate  Control molds and bacteria in foods and cosmetics  Nitrite prevents endospore germination  Antibiotics. Nisin and natamycin prevent spoilage of cheese

26. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Disinfectants  Aldehydes  Inactivate proteins by cross-linking with functional groups (–NH 2, –OH, –COOH, –SH)  Glutaraldehyde, formaldehyde, and ortho- phthalaldehyde

27. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Disinfectants  Gaseous sterilants  Denature proteins  Ethylene oxide

28. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Disinfectants  Peroxygens  Oxidizing agents  O 3, H 2 O 2, peracetic acid

29. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microbial Characteristics and Microbial Control Figure 7.11

30. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microbial Characteristics and Microbial Control Table 7.7