Transcript Chapter 7 - Farmasi Unand

Control of Microbial Growth
Chapter 7
History
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Humans vs. Microbes
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infections
diseases
plagues
epidemics
pandemics
Nursery Rhyme
Ring- a - ring of rosies
Pocketful of posies
Achoo ! Achoo !
We all fall down.
Bubonic Plague or the Black Death
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Epidemic swept thru Europe in the Middle
Ages (13th and 14th centuries)
40 million people were killed
• About 1/3 of the population of the continent
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Etiological agent:
• Yersinia pestis
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2 Vectors
• Rat
• Flea
Gram (-) rod
Yersinia pestis - Gram (-) bacillus
Vectors - Rat and Flea
Bubonic Plague Infection
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1. Flea bite with Yersinia pestis
2. Bacteria multiply in the bloodstream
• Bacteremia
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3. Bacteria localize in lymph nodes,
especially axillary and groin areas
4. Hemorrhaging occurs in lymph nodes, resulting in
“black and blue” swellings or Buboes (hence the name
Bubonic Plague or Black Death)
Bubonic Plague Infection
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5. If untreated, about 50 % Mortality Rate
6. If bacteria spread to the lungs, it becomes
Pneumonic Plague and is now highly
contagious (Almost a 99 % Mortality Rate)
Nursery Rhyme
Ring - a - ring of rosies,
A pocketful of posies
Achoo ! Achoo !
We all fall down.
“ I wouldn’t touch it with a 10’ pole”
Humans vs. Microbes
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1. Most of History, microbes have been
winning the battle
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2. In the last 100 yrs or so the battle has
swung in our favor
• Why?
• Because of our increasing knowledge of how to
Control Microbial Growth
Smallpox
Variola virus
Eradicated in 1977 (Somalia)
Methods to Control Microbial
Growth
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1. Physical
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2. Chemical
Terms used:
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Sterilization vs. Disinfection
Sterilization
• destroying all forms of life
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Disinfection
• destroying pathogens or unwanted organisms
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Disinfectant vs. Antiseptic
Disinfectant
• antimicrobial agent used on inanimate objects
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Antiseptic
• antimicrobial agent used on living tissue
cidal vs. static
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Bactericidal - kills bacteria
Bacteristatic - inhibits bacterial growth
Fungicidal
Fungistatic
Algacidal
Algastatic
Factors that effect Antimicrobial
Activity
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1. Temp
2. Time
3. Concentration of Antimicrobial agent
4. Type of Microbe
5. Activity of Microbe
6. Presence of organic matter
Targets of Antimicrobial Agents
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1. Cell membrane
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2. Enzymes & Proteins
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3. DNA & RNA
Physical Methods of Microbial Control
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1. Heat
• works by denaturing enzymes and proteins
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A. Thermal Death Point (TDP)
• lowest temp. at which all microorganism in a
liquid culture are killed in 10 minutes
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B. Thermal Death Time (TDT)
• minimum length of time in which all
microorganisms in a liquid culture are killed at
a given temperature
Moist Heat
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1. Boiling Water
• kills vegetative bacterial cells, Fungi and many
viruses
• not effective for endospores and some viruses
• Hepititis (20 min)
• Some spores may survive boiling water for up
to 20 hrs
Moist Heat
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2. Autoclave (Steam under pressure)
• preferred method of sterilization
• Water boils at 100 C
• Increasing the pressure raises the Temp.
• 15 lbs./ per sq. inch (psi) ------> 121 C
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121 C for 15 min.
Kilit Ampule
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Spores of Bacillus stearothermophilus
fermentable sugar
pH indicator
• basic - red
• acid - yellow
Dry Heat
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1. Direct Flaming
• Inoculating Loop and Needle 100% effective
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2. Incineration
• disposable wastes (paper cups, bags, dressings)
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3. Hot Air Sterilization
• Oven ( 170 C for 2 hours)
• used on substances that would be damaged by
moist heat sterilization
• gauzes, dressings or powders
Filtration
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Removes microorganisms from solutions
that might be damaged by heat
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culture media
enzymes
vaccines
antibiotics
Radiation
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1. Ionizing Radiation
• gamma rays & x-rays
• penetrates most substances
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Used on substances that could be damaged
by heat
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plastic petri dishes
plastic syringes
catheters
surgical gloves
Radiation
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2. Non-Ionizing Radiation
• UV Light
• does not penetrate plastic, glass or proteinaceous
matter
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Used to reduce microbial populations
• hospital rooms
• nurseries
• operating rooms
Thymine Dimers
Pasteurization
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Disinfection - not sterilization (removes
unwanted organisms)
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Mycobacterium tuberculosis
63 C for 30 minutes
72 C for 15 seconds (HTST)
Thermodurics
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• able to survive high temps.
Methods used to control Microbial Growth
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1. Heat
• Moist Heat
• Boiling Water
• Steam Heat (Autoclave)
• Dry Heat
• Direct Flaming
• Incineration
• Hot Air Sterilization (Oven)
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2. Filtration
 3. Radiation
• Ionizing Radiation
• Non-Ionizing Radiation
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4. Pasteurization (Heat)