Control of microbial growth Why control Prevent spoilage or loss Prevent infection or clear an infec

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Control of microbial growth Why control?
Prevent spoilage or loss Prevent
infection or clear an infection
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CONTROL OF MICROBIAL GROWTH Sterilization - kill
all organisms Disinfection - reduce
pathogens Antiseptic - agent to kill pathogens
on skin Disinfectant - reduce/kill pathogens on
surfaces Bacteriostasis - inhibit bacterial
growth Asepsis - keep pathogens out Aseptic
technique Sanitization - reduce pathogens on
surfaces to acceptably safe public health
levels
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CONTROL OF MICROBIAL GROWTH Physical
methods Chemical methods
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PHYSICAL CONTROL METHODS Temperature - moist
heat, dry heat Boiling - 10 min for cells,
hours for spores Autoclave - 10-15 min for
spores Pasteurization - 63ºC for 30 min
72ºC for 15 sec 140ºC for 3 sec Dry heat
- 160-180ºC for 2-3 hr Refrigeration Freezing
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PHYSICAL CONTROL METHODS Filtration Desiccation
Radiation x-rays or gamma rays UV
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CHEMICAL CONTROL METHODS Ideal
agent Effective against many types of
organisms Effective at low concentration Non-t
oxic to humans Stable Cheap Selecting an
agent What organism? What object?
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CHEMICAL CONTROL METHODS Antiseptics
Disinfectants Phenol related compounds Phenol
coefficient highest dilution of agent to
kill in 10 min, not 5 highest dilution of
phenol to kill in 10 min, not 5 Chlorhexidine Ha
logens I2 iodophor Cl2 hypochlorite Tincture
of iodine Alcohols Heavy metals Surfactants
quarternary nitrogen compounds
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CHEMICAL CONTROL METHODS Antibiotics Natural
vs. Synthetic Therapeutic dose vs. Toxic dose
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History of Antibiotics 1905 Erlich - Salvarsan,
an arsenic containing compound 1932 Domagk -
Prontosil, a red dye converted in blood to
sulfanilamide 1930s Fleming - Penicillin
1940s Waksman - Streptomycin
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Combination therapy - two or more at the same
time synergistic vs. antagonistic
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Antibiotic therapy Adverse
reactions allergic reactions - anaphylaxis or
anaphylactic shock toxic effects suppression of
normal flora
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CHEMICAL CONTROL METHODS Antibiotics Natural
vs. Synthetic Therapeutic dose vs. Toxic dose
Targets Cell wall Protein
synthesis Nucleic acid synthesis Metabolism
blockers Membrane function
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Cell wall synthesis penicillin family
vancomycin bacitracin
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Penicillin family
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Penicillin family ß-lactam compounds
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Penicillin family
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Protein synthesis
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Metabolism blockers Sulfanilamide
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Nucleic acid synthesis Rifamycin Rifampin -
blocks RNA synthesis Naldixic acid - blocks
DNA gyrase Quinolones Fluorquinolone -
blocks DNA gyrase Acyclovir - blocks DNA
synthesis in viruses Azidothymidine - AZT -
blocks DNA synthesis Zidovudine
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Antibiotic resistance Resistance plasmids
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Antibiotic resistance - MIC test
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Antibiotic resistance - Kirby-Bauer or
sensitivity disc assay
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Antiviral drug targets
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