Biology 120 lecture 5 2011 2012
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This document outlines a lecture on controlling microbial growth. It defines terms like sterilization, disinfection, and antisepsis. It discusses conditions that influence the effectiveness of antimicrobial agents like population size, composition, concentration, and duration of exposure. Physical methods of control like heat and filtration are described. Heat can kill microbes through degradation of nucleic acids and denaturation of proteins. The use of heat to sterilize foods is discussed.
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Biology 120 lecture 5 2011 2012
- 1. CONTROL OF MICROORGANISMS Lecture 5 Thursday, September 15, 2011
- 2. LECTURE OUTLINE Definition of Terms in Microbial Control Pattern of Microbial Death Conditions Influencing the Effectiveness of Antimicrobial Agents Use of Physical Agents Use of Chemical Agents Thursday, September 15, 2011
- 3. Thursday, September 15, 2011
- 4. The Control of Microbial Growth SEPSIS microbial contamination ASEPSIS absence of significant contamination Thursday, September 15, 2011
- 5. The Control of Microbial Growth SEPSIS microbial contamination ASEPSIS absence of significant contamination Thursday, September 15, 2011
- 6. The Control of Microbial Growth STERILIZATION Removal of all microbial life COMMERCIAL STERILIZATION Killing C. botulinum endospores Thursday, September 15, 2011
- 7. The Control of Microbial Growth STERILIZATION Removal of all microbial life COMMERCIAL STERILIZATION Killing C. botulinum endospores Thursday, September 15, 2011
- 8. The Control of Microbial Growth DISINFECTION Removal of pathogens ANTISEPSIS from living tissue DEGERMING from a limited area Thursday, September 15, 2011
- 9. The Control of Microbial Growth DISINFECTION Removal of pathogens ANTISEPSIS from living tissue DEGERMING from a limited area Thursday, September 15, 2011
- 10. The Control of Microbial Growth SANITATION Lower microbial counts on eating utensils BIOCIDE/GERMICIDE: Kills microbes BACTERIOSTATS: Inhibiting, not killing, microbes Thursday, September 15, 2011
- 11. The Control of Microbial Growth SANITATION Lower microbial counts on eating utensils BIOCIDE/GERMICIDE: Kills microbes BACTERIOSTATS: Inhibiting, not killing, microbes Thursday, September 15, 2011
- 12. PATTERN OF MICROBIAL DEATH Bacterial populations die at a constant logarithmic rate Thursday, September 15, 2011
- 13. PATTERN OF MICROBIAL DEATH Bacterial populations die at a constant logarithmic rate Thursday, September 15, 2011
- 14. The Control of Microbial Growth HOW DO WE DECIDE WHETHER THEY ARE ACTUALLY DEAD? Thursday, September 15, 2011
- 15. The Control of Microbial Growth HOW DO WE DECIDE WHETHER THEY ARE ACTUALLY DEAD? Thursday, September 15, 2011
- 16. The Control of Microbial Growth HOW DO WE DECIDE WHETHER THEY ARE ACTUALLY DEAD? “a microbe is defined DEAD if it does not grow when inoculated into culture medium that would normally support its growth” Thursday, September 15, 2011
- 17. Conditions Influencing Effectiveness of Antimicrobial Agent Activity 1. Population size Larger population requires a longer time to die 2. Population composition Microorganisms vary markedly on susceptibility Vegetative versus Spores Young versus Mature cells Thursday, September 15, 2011
- 18. Conditions Influencing Effectiveness of Antimicrobial Agent Activity 1. Population size Larger population requires a longer time to die 2. Population composition Microorganisms vary markedly on susceptibility Vegetative versus Spores Young versus Mature cells Thursday, September 15, 2011
- 19. Conditions Influencing Effectiveness of Antimicrobial Agent Activity 3. Concentration or Intensity of an Antimicrobial Agent The more concentrated an agent the more rapidly microbes can be destroyed BUT sometimes an agent may be more effective at lower concentrations (e.g. 70% alcohol) 4. Duration of Exposure The longer the exposure to an agent the more they will be killed Thursday, September 15, 2011
- 20. Conditions Influencing Effectiveness of Antimicrobial Agent Activity 3. Concentration or Intensity of an Antimicrobial Agent The more concentrated an agent the more rapidly microbes can be destroyed BUT sometimes an agent may be more effective at lower concentrations (e.g. 70% alcohol) 4. Duration of Exposure The longer the exposure to an agent the more they will be killed Thursday, September 15, 2011
- 21. Conditions Influencing Effectiveness of Antimicrobial Agent Activity 5. Temperature An increase in temperature at which a chemical acts often enhances it activity Example: acids used in high T = more effective 6. Local environment pH, organic matter, etc Controls or Protects the pathogen Thursday, September 15, 2011
- 22. Conditions Influencing Effectiveness of Antimicrobial Agent Activity 5. Temperature An increase in temperature at which a chemical acts often enhances it activity Example: acids used in high T = more effective 6. Local environment pH, organic matter, etc Controls or Protects the pathogen Thursday, September 15, 2011
- 23. Thursday, September 15, 2011
- 24. PHYSICAL METHODS: HEAT Fire and boiling Sufficient to destroy vegetative cells (10 minutes) Not high for killing endospores Disinfection but not sterilization! Thursday, September 15, 2011
- 25. PHYSICAL METHODS: HEAT Fire and boiling Sufficient to destroy vegetative cells (10 minutes) Not high for killing endospores Disinfection but not sterilization! Thursday, September 15, 2011
- 26. PHYSICAL METHODS: HEAT Thermal Death Point (TDP) The lowest temperature at which a microbial suspension in killed in 10 minutes Thermal Death Time (TDT) The shortest time needed to kill all organisms in a microbial suspension at a specific temperature and under defined conditions Thursday, September 15, 2011
- 27. PHYSICAL METHODS: HEAT Thermal Death Point (TDP) The lowest temperature at which a microbial suspension in killed in 10 minutes Thermal Death Time (TDT) The shortest time needed to kill all organisms in a microbial suspension at a specific temperature and under defined conditions Thursday, September 15, 2011
- 28. However, such a destruction is logarithmic and it is theoretically NOT POSSIBLE to “completely destroy” microbes in a sample Thursday, September 15, 2011
- 29. However, such a destruction is logarithmic and it is theoretically NOT POSSIBLE to “completely destroy” microbes in a sample Thursday, September 15, 2011
- 30. However, such a destruction is logarithmic and it is theoretically NOT POSSIBLE to “completely destroy” microbes in a sample Decimal Reduction Time or D value Time required to kill 90% of the microorganisms or spores in a sample at a specified temperature Time required for the line to drop by one log cycle or tenfold Used to estimate the relative resistance of a microbe to different temperatures Thursday, September 15, 2011
- 31. PHYSICAL METHODS: HEAT Thursday, September 15, 2011
- 32. PHYSICAL METHODS: HEAT Thursday, September 15, 2011
- 33. PHYSICAL METHODS: HEAT z Value The increase in temperature required to reduce D to 1/10 its value or to reduce it by one log cycle Thursday, September 15, 2011
- 34. PHYSICAL METHODS: HEAT z Value The increase in temperature required to reduce D to 1/10 its value or to reduce it by one log cycle F value Time in minutes at a specific temperature needed to kill a population of cells or spores Usually 121°C Thursday, September 15, 2011
- 35. APPLICATION: FOOD INDUSTRY Thursday, September 15, 2011
- 36. APPLICATION: FOOD INDUSTRY Thursday, September 15, 2011
- 37. APPLICATION: FOOD INDUSTRY After a food have been canned, it must be heated to eliminate the risk of botulism arising from the presence of Clostridium spores Thursday, September 15, 2011
- 38. APPLICATION: FOOD INDUSTRY After a food have been canned, it must be heated to eliminate the risk of botulism arising from the presence of Clostridium spores Example: (1012 to 100 spores) IF the D value = 0.204 minutes It would take 12D or 2.5 minutes to reduce the spore number by heating at the specified temperature Thursday, September 15, 2011
- 39. APPLICATION: FOOD INDUSTRY Thursday, September 15, 2011
- 40. APPLICATION: FOOD INDUSTRY Thursday, September 15, 2011
- 41. APPLICATION: FOOD INDUSTRY If the z value for Clostridium spores is 10°C Thursday, September 15, 2011
- 42. APPLICATION: FOOD INDUSTRY If the z value for Clostridium spores is 10°C It takes a 10°C change in temperature to alter the D value tenfold Thursday, September 15, 2011
- 43. APPLICATION: FOOD INDUSTRY If the z value for Clostridium spores is 10°C It takes a 10°C change in temperature to alter the D value tenfold Thursday, September 15, 2011
- 44. APPLICATION: FOOD INDUSTRY If the z value for Clostridium spores is 10°C It takes a 10°C change in temperature to alter the D value tenfold THUS: if the cans are to be processed at 111°C rather than 121°C, the D value would increase by tenfold t 2.04 minutes Thursday, September 15, 2011
- 45. APPLICATION: FOOD INDUSTRY If the z value for Clostridium spores is 10°C It takes a 10°C change in temperature to alter the D value tenfold THUS: if the cans are to be processed at 111°C rather than 121°C, the D value would increase by tenfold t 2.04 minutes The 12D value = 24.5 minutes Thursday, September 15, 2011
- 46. PHYSICAL METHODS: HEAT (MOIST HEAT STERILIZATION) Thursday, September 15, 2011
- 47. PHYSICAL METHODS: HEAT (MOIST HEAT STERILIZATION) Thursday, September 15, 2011
- 48. PHYSICAL METHODS: HEAT (Dry Heat Sterlization) Hot-air Autoclave Equivalent treatments 170˚C, 2 hr 121˚C, 15 min Thursday, September 15, 2011
- 49. PHYSICAL METHODS: HEAT (Dry Heat Sterlization) Hot-air Autoclave Equivalent treatments 170˚C, 2 hr 121˚C, 15 min Thursday, September 15, 2011
- 50. PHYSICAL METHODS: HEAT (Dry Heat Sterlization) Flaming Hot-air Autoclave Equivalent treatments 170˚C, 2 hr 121˚C, 15 min Thursday, September 15, 2011
- 51. PHYSICAL METHODS: HEAT (Dry Heat Sterlization) Flaming Hot-air Autoclave Equivalent treatments 170˚C, 2 hr 121˚C, 15 min Thursday, September 15, 2011
- 52. PHYSICAL METHODS: HEAT (Dry Heat Sterlization) Flaming Incineration Hot-air Autoclave Equivalent treatments 170˚C, 2 hr 121˚C, 15 min Thursday, September 15, 2011
- 53. PHYSICAL METHODS: HEAT (Dry Heat Sterlization) Flaming Incineration Hot-air Autoclave Equivalent treatments 170˚C, 2 hr 121˚C, 15 min Thursday, September 15, 2011
- 54. PHYSICAL METHODS: HEAT (Dry Heat Sterlization) Flaming Incineration Hot-air sterilization Hot-air Autoclave Equivalent treatments 170˚C, 2 hr 121˚C, 15 min Thursday, September 15, 2011
- 55. HOW DOES HEAT KILL MICROBES Thursday, September 15, 2011
- 56. HOW DOES HEAT KILL MICROBES Thursday, September 15, 2011
- 57. HOW DOES HEAT KILL MICROBES MOIST HEAT Kill effectively by degradation of nucleic acids and by denaturation of enzymes and other essential proteins May also disrupt cell membranes Thursday, September 15, 2011
- 58. HOW DOES HEAT KILL MICROBES MOIST HEAT Kill effectively by degradation of nucleic acids and by denaturation of enzymes and other essential proteins May also disrupt cell membranes Thursday, September 15, 2011
- 59. HOW DOES HEAT KILL MICROBES MOIST HEAT Kill effectively by degradation of nucleic acids and by denaturation of enzymes and other essential proteins May also disrupt cell membranes DRY HEAT Microbial death results from the oxidation of cell constituents and denaturation of proteins Thursday, September 15, 2011
- 60. PHYSICAL METHODS: FILTRATION Applicable for heat-sensitive materials that needs sterilization Types of filters Depth filters: consist of fibrous or granular materials that have been bonded into a thick layer filled with twisting channels of small diameter Membrane filters: porous membranes; 0.2 µm pore sizes Thursday, September 15, 2011
- 61. PHYSICAL METHODS: FILTRATION Applicable for heat-sensitive materials that needs sterilization Types of filters Depth filters: consist of fibrous or granular materials that have been bonded into a thick layer filled with twisting channels of small diameter Membrane filters: porous membranes; 0.2 µm pore sizes Thursday, September 15, 2011
- 62. PHYSICAL METHODS: FILTRATION Laminar flow hood versus biological safety cabinets (HEPA filters) High Efficiency Particulate Air Remove 99.97% particles 0.02 µm for sterilizing AIR Thursday, September 15, 2011
- 63. PHYSICAL METHODS: FILTRATION Laminar flow hood versus biological safety cabinets (HEPA filters) High Efficiency Particulate Air Remove 99.97% particles 0.02 µm for sterilizing AIR Thursday, September 15, 2011
- 64. BIOSAFETY CABINETS Class1 (from room=outside) protection: person and environment Class 2 (Type A and B) ) Type A and B: product, person and environment difference: type A air is recirculated back to room, type B exhausted outside the building Class 3: contained facility, higher level of protection and containment Thursday, September 15, 2011
- 65. BIOSAFETY CABINETS Class1 (from room=outside) protection: person and environment Class 2 (Type A and B) ) Type A and B: product, person and environment difference: type A air is recirculated back to room, type B exhausted outside the building Class 3: contained facility, higher level of protection and containment Thursday, September 15, 2011
- 66. PHYSICAL METHODS: RADIATION IONIZING RADIATION X rays, gamma rays, electron beams Excellent as a sterilizing agent and penetrates deep into objects NON-IONIZING RADIATION UV (about 260nm) Quite lethal but does not penetrate glass, dirt films, water and other substances very effectively Microwaves: kill by heat not usually antimicrobial Thursday, September 15, 2011
- 67. PHYSICAL METHODS: RADIATION IONIZING RADIATION X rays, gamma rays, electron beams Excellent as a sterilizing agent and penetrates deep into objects NON-IONIZING RADIATION UV (about 260nm) Quite lethal but does not penetrate glass, dirt films, water and other substances very effectively Microwaves: kill by heat not usually antimicrobial Thursday, September 15, 2011
- 68. Thursday, September 15, 2011
- 69. CHEMICAL AGENTS Thursday, September 15, 2011
- 70. CHEMICAL METHODS PHENOLICS QUATERNARY AMMONIUM ALCOHOLS COMPOUNDS ALDEHYDES HALOGENS STERILIZING HEAVY METALS GASES Thursday, September 15, 2011
- 71. CHEMICAL METHODS PHENOLICS QUATERNARY AMMONIUM ALCOHOLS COMPOUNDS ALDEHYDES HALOGENS STERILIZING HEAVY METALS GASES Thursday, September 15, 2011
- 72. CHEMICAL METHODS Chemical agent Effectiveness against Endospores Mycobacteria Phenolics Poor Good Quats None None Chlorines Fair Fair Alcohols Poor Good Glutaraldehyde Fair Good Thursday, September 15, 2011
- 73. CHEMICAL METHODS Chemical agent Effectiveness against Endospores Mycobacteria Phenolics Poor Good Quats None None Chlorines Fair Fair Alcohols Poor Good Glutaraldehyde Fair Good Thursday, September 15, 2011
- 74. CHEMICAL METHODS: Phenolics First widely used antiseptic and disinfectant Joseph Lister (1867): reduced the risk of infection during operations Example: LYSOLR Act by denaturing proteins and disrupting cell membranes Thursday, September 15, 2011
- 75. CHEMICAL METHODS: Phenolics First widely used antiseptic and disinfectant Joseph Lister (1867): reduced the risk of infection during operations Example: LYSOLR Act by denaturing proteins and disrupting cell membranes Thursday, September 15, 2011
- 76. Disruption of Cell Membranes Thursday, September 15, 2011
- 77. CHEMICAL METHODS: Phenolics ADVANTAGES: effective in the presence of organic material and remain active on surfaces long after application DISADVANTAGE: disagreeable odor and can cause skin irritation and in some instances brain damage (hexachlorophene) Thursday, September 15, 2011
- 78. CHEMICAL METHODS: Phenolics ADVANTAGES: effective in the presence of organic material and remain active on surfaces long after application DISADVANTAGE: disagreeable odor and can cause skin irritation and in some instances brain damage (hexachlorophene) Thursday, September 15, 2011
- 79. CHEMICAL METHODS: Alcohols Widely used disinfectant and antiseptics Bactericidal and fungicidal but not sporicidal May not destroy lipid-containing viruses Thursday, September 15, 2011
- 80. CHEMICAL METHODS: Alcohols Widely used disinfectant and antiseptics Bactericidal and fungicidal but not sporicidal May not destroy lipid-containing viruses Thursday, September 15, 2011
- 81. DENATURES PROTEINS, DISSOLVES LIPIDS Thursday, September 15, 2011
- 82. CHEMICAL METHODS: Alcohols Example: ethanol and isopropanol (70-80% concentration) Act by denaturing proteins and possibly by dissolving membrane lipids 10-15 soaking in alcohol is sufficient to disinfect thermometers and small instruments Thursday, September 15, 2011
- 83. CHEMICAL METHODS: Alcohols Example: ethanol and isopropanol (70-80% concentration) Act by denaturing proteins and possibly by dissolving membrane lipids 10-15 soaking in alcohol is sufficient to disinfect thermometers and small instruments Thursday, September 15, 2011
- 84. CHEMICAL METHODS: Halogens Iodine Kills by oxidizing cell constituents and iodinating cell proteins Kill spores at high concentrations DISADVANTAGE: a stain may be left (answer = iodophor) Thursday, September 15, 2011
- 85. CHEMICAL METHODS: Halogens Iodine Kills by oxidizing cell constituents and iodinating cell proteins Kill spores at high concentrations DISADVANTAGE: a stain may be left (answer = iodophor) Thursday, September 15, 2011
- 86. CHEMICAL METHODS: Halogens Chlorine Usually for water supply Kills by oxidation of cellular materials and destruction of vegetative bacteria, fungi Will not kill spores Death within 30 minutes Thursday, September 15, 2011
- 87. CHEMICAL METHODS: Halogens Chlorine Usually for water supply Kills by oxidation of cellular materials and destruction of vegetative bacteria, fungi Will not kill spores Death within 30 minutes Thursday, September 15, 2011
- 88. CHEMICAL METHODS: Heavy Metals Mercury, Arsenic, Zinc, Copper Used as germicides How do they Kill: Heavy metals combine with proteins, often with their sulfhydryl groups and inactivate them May also precipitate cell proteins Thursday, September 15, 2011
- 89. CHEMICAL METHODS: Heavy Metals Mercury, Arsenic, Zinc, Copper Used as germicides How do they Kill: Heavy metals combine with proteins, often with their sulfhydryl groups and inactivate them May also precipitate cell proteins Thursday, September 15, 2011
- 90. CHEMICAL METHODS: Quats DETERGENTS Amphipathic (both polar and non-polar ends) Kill by disrupting microbial membranes and denature proteins ADVANTAGE: stable, non-toxic DISADVANTAGE: inactivated by hard Thursday, September 15, 2011
- 91. CHEMICAL METHODS: Quats DETERGENTS Amphipathic (both polar and non-polar ends) Kill by disrupting microbial membranes and denature proteins ADVANTAGE: stable, non-toxic DISADVANTAGE: inactivated by hard Thursday, September 15, 2011
- 92. Soap Degerming Surface-Active Agents or Surfactants Acid-anionic Sanitizing detergents Quarternary Bactericidal, Denature ammonium proteins, disrupt compounds plasma membrane Cationic detergents Thursday, September 15, 2011
- 93. CHEMICAL METHODS: Aldehydes FORMALDEHYDES Very reactive molecules that combine with proteins and inactivate them Sporicidal and can be used as sterilants Thursday, September 15, 2011
- 94. CHEMICAL METHODS: Aldehydes FORMALDEHYDES Very reactive molecules that combine with proteins and inactivate them Sporicidal and can be used as sterilants Thursday, September 15, 2011
- 95. EVALUATION OF ANTIMICROBIAL AGENT EFFECTIVENESS PHENOL COEFFICIENT TEST Best-known disinfectant screening test Potency of a disinfectant is compared with that of phenol The highest dilution that killed bacteria after a 10 minutes exposure are used to calculate phenol coefficient Thursday, September 15, 2011
- 96. EVALUATION OF ANTIMICROBIAL AGENT EFFECTIVENESS PHENOL COEFFICIENT TEST Best-known disinfectant screening test Potency of a disinfectant is compared with that of phenol The highest dilution that killed bacteria after a 10 minutes exposure are used to calculate phenol coefficient Thursday, September 15, 2011
- 97. CALCULATING PHENOL COEFFICIENTS The reciprocal of the appropriate test disinfectant dilution is divided by that for phenol to obtain the coefficient Example: phenol dilution = 1/90 and the maximum effective dilution for disinfectant X = 1/450 Phenol coefficient = 5 Thursday, September 15, 2011
- 98. CALCULATING PHENOL COEFFICIENTS The reciprocal of the appropriate test disinfectant dilution is divided by that for phenol to obtain the coefficient Example: phenol dilution = 1/90 and the maximum effective dilution for disinfectant X = 1/450 Phenol coefficient = 5 Thursday, September 15, 2011
- 99. CALCULATING PHENOL COEFFICIENTS The higher the phenol coefficient value, the more effective the disinfectant under this conditions Thursday, September 15, 2011
- 100. CALCULATING PHENOL COEFFICIENTS The higher the phenol coefficient value, the more effective the disinfectant under this conditions Thursday, September 15, 2011
- 101. DILUTION TESTS Metal rings dipped in test bacteria are dried Dried cultures placed in disinfectant for 10 min at 20°C Rings transferred to culture media to determine whether bacteria survived treatment Thursday, September 15, 2011
- 102. DILUTION TESTS Metal rings dipped in test bacteria are dried Dried cultures placed in disinfectant for 10 min at 20°C Rings transferred to culture media to determine whether bacteria survived treatment Thursday, September 15, 2011
- 103. DISK-DIFFUSION METHOD Thursday, September 15, 2011
- 104. DISK-DIFFUSION METHOD Thursday, September 15, 2011
- 105. CHEMOTHERAPEUTIC AGENTS Thursday, September 15, 2011
- 106. CHEMOTHERAPEUTIC AGENTS Thursday, September 15, 2011
- 107. CHEMOTHERAPEUTIC AGENTS Antibiotics are medicines used to treat infections caused by bacteria only Infections are usually caused by bacteria or viruses Antibiotics, therefore, do not cure all infections Many infections like the common cold, flu, mild sore throat or diarrhea are caused by viruses Thursday, September 15, 2011
- 108. CHEMOTHERAPEUTIC AGENTS Antibiotics are medicines used to treat infections caused by bacteria only Infections are usually caused by bacteria or viruses Antibiotics, therefore, do not cure all infections Many infections like the common cold, flu, mild sore throat or diarrhea are caused by viruses Thursday, September 15, 2011
- 109. Thursday, September 15, 2011
- 110. WHAT IF ANTIBIOTICS WERE USED INCORRECTLY? No healing effect - If antibiotics are used for viral infections, there will be no effect on the illness Antibiotic resistance - This occurs when one antibiotic no longer works on a specific type of bacteria A stronger antibiotic will be needed to treat the infection caused by this resistant strain of bacteria Thursday, September 15, 2011
- 111. WHAT IF ANTIBIOTICS WERE USED INCORRECTLY? No healing effect - If antibiotics are used for viral infections, there will be no effect on the illness Antibiotic resistance - This occurs when one antibiotic no longer works on a specific type of bacteria A stronger antibiotic will be needed to treat the infection caused by this resistant strain of bacteria Thursday, September 15, 2011
- 112. ANTIBIOTIC MECHANISMS Thursday, September 15, 2011
- 113. ANTIBIOTIC MECHANISMS Thursday, September 15, 2011
- 114. RESISTANCE Thursday, September 15, 2011
- 115. RESISTANCE Thursday, September 15, 2011
- 116. RESISTANCE Thursday, September 15, 2011
- 117. RESISTANCE Thursday, September 15, 2011
- 118. DO YOU CONTRIBUTE TO RESISTANCE? Thursday, September 15, 2011
- 119. DO YOU CONTRIBUTE TO RESISTANCE? Thursday, September 15, 2011
- 120. DO YOU CONTRIBUTE TO RESISTANCE? Thursday, September 15, 2011
- 121. DO YOU CONTRIBUTE TO RESISTANCE? Thursday, September 15, 2011
- 122. DO YOU CONTRIBUTE TO RESISTANCE? Another factor that contributes to resistance is that when patients are prescribed antibiotics for a just cause, many do not finish their medication This allows resistant bacteria to survive more easily The practice of saving unused medication to treat themselves or others at a later date can also lead to resistant strains Thursday, September 15, 2011
- 123. DO YOU CONTRIBUTE TO RESISTANCE? Thursday, September 15, 2011
- 124. DO YOU CONTRIBUTE TO RESISTANCE? Thursday, September 15, 2011
- 125. DO YOU CONTRIBUTE TO RESISTANCE? Also contributing to antibiotic resistance is the widespread use of antibiotics to promote weight gain and to control disease in cattle, pigs, and chickens Forty to fifty percent of antibiotics produced are used in livestock feed This leads to an increase of resistant bacteria in these animals, which is then spread to humans Thursday, September 15, 2011
- 126. ANY QUESTIONS??? Thursday, September 15, 2011
- 127. NEXT MEETING: INTERACTIVE LECTURE/ QUIZ ON METABOLISM Thursday, September 15, 2011