2. Control of Microorganisms

3. Control of Microbial Growth Effected in two basic ways: 1.By Killing Microorganisms 2.By inhibiting the Growth of Microorganisms Usually involves the use of: 1.Physical Agents 2.Chemical Agents

4. Principles of Microbial Control (Definitions) Prevention / Control of Growth to Prevent Infection and Spoilage

5. Principles of Microbial Control (Definitions) Sterilization / Complete Destruction - No degrees of sterilization (All or Nothing) -

6. Principles of Microbial Control Disinfection / Reducing Growth Nonliving Surfaces

7. Principles of Microbial Control Antisepsis / Reducing Growth on Living Tissue

8. Principles of Microbial Control Antisepsis / Reducing Growth on Living Tissue Antiseptics are generally less toxic than disinfectants because they must not cause too much damage to the host living tissue. Examples of antiseptics include iodine, 70% ethanol and 3% hydrogen peroxide.

9. Principles of Microbial Control Sanitize Subject to High Temperature Washing (Dishwashers)

10. Principles of Microbial Control Cide – Suffix Meaning to Kill Stat – Suffix Meaning to Inhibit Sepsis – Bacterial Contamination Asepsis – Lack of Bacterial Contamination

11. Time to Kill in Proportion to the Population Size Large Numbers Require Greater Time Small Numbers Require Less Time

12. Susceptibilities Vary Endospores are Difficult to Kill Organic Matter May Interfere with Heat Treatments and Chemical Control Agents

13. Control Agents Act By Alteration of Membrane Permeability - Susceptibility of membrane is due to its lipid and protein composition - Control Agents can alter permeability Damage to Proteins and Nucleic Acids - Break hydrogen and covalent bonds in proteins - Interfere with DNA, RNA, Protein Synthesis

14. Types of methods Physical Chemical

15. Physical Methods of Microbial Control

16. Physical Methods Heat Filtration Low Temperatures Desiccation Osmotic Pressure Radiation

17. Heat Most Frequent and Widely Used. 1. Type of Heat –Moist –Dry 2. Time of Application 3. Temperature

18. Thermal Death Point (TDP) / Lowest Temp to Kill All the Bacteria in a Broth in 10 Minutes Thermal Death Time (TDT) / Time Span Required to Kill All the Bacteria in a Broth at a Given Temperature Decimal Reduction Time (DRT) / Length of Time in Which 90% of a Bacterial Population will be Killed at a given Temperature Boiling / Kills Many Vegetative Cells and Inactivates Viruses Within 10 Minutes

19. Moist Heat Sterilization Boiling Autoclaving

20. Boiling 100° C for 30 Minutes Kills Everything Except Some Endospores

21. Autoclaving Steam Under Pressure 121° C for 15 Minutes at 15 lb/in 2 Heat-labile Substances will be Denatured Steam Must Contact the Material

22. Dry Heat Sterilization Direct Flaming Incineration Hot-Air Sterilization (Oven)

23. Incineration Burns and Physically Destroys Organisms Used for a. Needles b. Inoculating Wires

24. Dry Heat (Hot Air Oven) 160° C for 2 Hours or 170° C for 1 hour Used for a. Glassware b. Metal c. Objects That Won’t Melt

25. Pasteurization A High Temperature Is Used For a Short Time Batch Method –63°C for 30 Minutes – 71 for 15 seconds (UHT) sterilization 140°C for 3 seconds. –2 months with only minimal changes in flavor.

26. Filtration The passage of a liquid or gas through a filter with pores small enough to retain microbes. Especially important to sterilize solutions which would be denatured by heat (antibiotics, injectable drugs, amino acids, vitamins.)

27. HEPA Filters HEPA filters are High-Efficiency Particulate Air filters designed for the filtration of small particles. Certified HEPA filters must capture a minimum of 99.97% of 0.3 microns contaminants.

28. Low Temperatures Decreasing Temperature Decreases Chemical Activity Low Temps are Not Bactericidal

29. Desiccation Disrupts Microbial Metabolism Stops Growth / Microbes Are Still Viable Freeze-drying / Dehydration Viruses and Endospores Can Resist Desiccation

31. Osmotic Pressure Plasmolysis Sugar Curing / Salting May Still Get Some Mold or Yeast Growth

32. Radiation Ionizing Radiation 1. High Degree of Penetration 2. Examples - Gamma Rays - X-rays - High Energy Electron Beams NonIonizing Radiation 1. Low Degree of Penetration 2. Harmful / Skin / Eyes 3. Cell Damage / Thymine 4. Germicidal / 260 nm 5. Example: Ultraviolet

33. Ionizing Radiation Ionizing radiation (gamma radiation) can penetrate deeper into objects, and is used to sterilize food, drugs, and medical supplies

34. Chemical Control Methods Phenols and Phenolics Halogens Alcohols Heavy Metals and Their Compounds Surface-Active Agents Quaternary Ammonium Compounds Chemical Food Preservatives Aldehydes

37. Types of Disinfectants Phenol and Phenolics - Exert Influence By 1. Injuring Plasma membranes (lipids) 2. Inactivating Enzymes 3. Denaturing Proteins Not effective against spores

38. Types of Disinfectants Halogens - Can be Used Alone or in Solution - Chlorine -- Purifies Drinking Water a. Forms an Acid Which is Bactericidal b. Disinfectant in Gaseous Form or in Solution as Calcium Hypochlorite

39. Types of Disinfectants Halogens - Iodine – combines with Amino Acids a. Inactivates Enzymes b. Tincture / Alcohol

40. Types of Disinfectants Alcohols - Denature Proteins - Dissolve Lipids - Tinctures - Wet Disinfectants a. Aqueous Ethanol (60% - 95%) b. Isopropal Alcohol

41. Types of Disinfectants Heavy Metals and Their Compounds - Used for Burn Treatment - Prevents Neonatal Gonorrheal Opthalmia - Denature Proteins - Example / Silvadene Ointment / Silver

42. Types of Disinfectants Surface-Active Agents - Decrease Molecular Surface Tension - Include Soaps and Detergents - Soaps Have Limited Germicidal Action but Assist in the Removal of Organisms by Scrubbing - Acid-Anionic Detergents / Dairy

43. Types of Disinfectants Quaternary Ammonium Compounds (QUATS) - Cationic Detergents Attached to NH 4 +1 - Disrupt Plasma Membranes - Most Effective on Gram-Positive Bacteria - Mouthwashes and Sore Throat Remedies

44. Types of Disinfectants Chemical Food Preservatives - Sorbic Acid - Benzoic AcidInhibitFungus - Propionic Acid - Nitrate and Nitrite Salts / Meats / To Prevent Germination of Clostridium botulinum endospores

45. Types of Disinfectants Aldehydes - Formaldehyde - Glutaraldehyde - Inactivate proteins by cross-linking with functional groups (–NH 2, –OH, – COOH, —SH)

46. Antibiotics Cell wall antibiotics Bactracin Cycloserine Vancomycin Penicillin and beta lactam antibiotics Cell menbrane antibiotics DNA Synthesis Inhibitors RNA Synthesis Inhibitors Protein Synthesis Inhibitors Metabolism