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 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 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 Phenol coefficient- compares the effectiveness of a disinfectant against the effectiveness of phenol. 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. cresols from coal tar as O- phenylphenol (Lysol) Injury lipid containing plasma membrane, Active in present of organic compound. good surface disinfectant Bisphenols Hexachlorophene. HAI control Triclosan, soap, toothpaste. (G +ve), fungi Disrupt plasma membranes

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Biguanides. Chlorhexidine Disrupt plasma membranes Effect on most bacteria except mycobacterium, endospores, non envolpe viruses, protozoa cyst. Used as mouthwash, for general skin cleansing, a surgical scrub, and a preoperative skin preparation. Types of Disinfectants

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Halogens. Iodine,active aganst all kind of bacteria, many endospores, fungi, some viruses. Proposed mechanisms by binding to some enzymes and protiens. Tincture iodin contain alcohol, Iodophor is acompination of iodine and organic molecule.eg povidone- iodine. Chlorine Oxidizing agents, Bleach is hypochlorous acid (HOCl) Chloramines consist of ammonia use as disinectant, antiseptic and santizing. 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 No effect on endospores, and non envelope viruses.

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heavy Metals. Ag, Hg, Cu Oligodynamic action, the ability of small amounts of heavy metals to exert a lethal effect on bacterial cells. The exact mechanism of this action is still unknown but some data suggest that the metal ions denature protein of the target cells by binding to reactive groups resulting in their precipitation and Inactivation. Silver nitrite used as antiseptic and eyes drop of newborns. Cupper sulfate used to control green algae in concentration part per million. Zinc oxide used in paints. Types of Disinfectants

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Surface-Active Agents or Surfactants Soaps and acid anionic detergents The agents decrease the surface tension among molecules of a liquid; soaps and detergents are examples. Soaps have limited germicidal action but assist in the removal of microorganisms through scrubbing. Acid-anionic detergents are used to clean dairy equipment.

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Quaternary Ammonium Compounds Quats are cationic detergents attached to NH 4 +. By disrupting the plasma membranes, they allow cytoplasmic constituents to leak out of the cell. Quats are most effective against Gram-positive bacteria, envelope viruses, fungi. They do not kill endospores or mycobacteria. Examples Zephiran (benzalkonium chloride) Cepacol (cetylpyridinium chloride) Pseudomonas are highly resistant, can even live in quats

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 Nitrate and nitrite salts prevent germination of Clostridium botulinum endospores in meats. Antibiotics. Nisin and natamycin antifungal prevent spoilage of cheese Types of Disinfectants

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Aldehydes Aldehydes such as formaldehyde and glutaraldehyde (Gidex). Inactivate proteins by cross-linking with functional groups (–NH 2, –OH, –COOH, —SH) Formaldehyde gas or formalin 37% of Formaldehyde. Glutaraldehyde used as 2% solution is bactericidal, virucidal, tuberculocidal in 10 min. Types of Disinfectants

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Chemicals that sterilize in a closed chamber Ethylene oxide is the gas most frequently used for sterilization. Other examples include propylene oxide and beta- propiolactone. It penetrates most materials and kills all microorganisms by protein denaturation. It requires long exposure and is toxic and explosive when in pure form. Gaseous Chemosterilizers

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Ozone, peroxide, and peracetic acid (CH 3 CO 3 H) are used as antimicrobial agents. They exert their effect by oxidizing molecules inside cells. Ozone supplement Cl in water disinfectant. Used on contaminated surfaces; some deep wounds, in which they are very effective against oxygen- sensitive anaerobes. Peroxygens (Oxidizing Agents)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Microbial Characteristics and Microbial Control Gram-negative bacteria are generally more resistant than gram-positive bacteria to disinfectants and antiseptics. Mycobacteria, endospores, and protozoan cysts and oocysts are very resistant to disinfectants and antiseptics. Non-enveloped viruses are generally more resistant than non-enveloped viruses to disinfectants and antiseptics.

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

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