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Chapter 7 The control of Microbial Growth (outside the body) prrevent infection
The removal or destruction of all life forms is?
Sterilization *when you flame the loop, it is sterilized.
Microbil contamination. *a pt. is septic, they have a severe bacterial infection, the bacteria are taking over their body.
absence of significant contamination. (*like when we clean our lab table) **aseptic surgery techniques prevent microbial contamination of wounds
Disinfectant vs. Antiseptic
a disinfectant is used on objects and antiseptic is used on living tisses. Antimicrobial chemicals, expected to destoy pathogens but not acheive sterilization.
infection pt. got in the hospital. IE: MRSA
removal of all microbial life (heat, filtration)
For food: Commercial sterilization
to kill C. botulinum endospores. (botulinum=one that has endospores; endospores are very tough if you destroy the endospores you destroy all other bacteria.
reduces microbial numbes to safe levels (e.g. eating utensils)
Capable of inhibiting rreproduction of bacteria. *-static = no growth=does not kill bacteria it inhibits its growth and yor immune system kill the bacteria
capable of killing bacteria
fungicide, sporicide, germicide, biocide
biocide or gernicide kills microorganisms (usually with certain exceptions, such as endospores); a fungicide kills fungi; a virocide inactivates viruses
Single most effective way of not speading germs?
Hand Washing *remember Pasteur, Semmelweis and Lister from Chapter 1
Rate of Microbial Death
Bacterial populations subjected to heat or antimicrobial chemicals die at a constant rate.
Decimal reduction time
time it takes for 90% of the bactera to die. Ex 1 million bacteria and 90% die in one min. 100,000 left, one more nimute 90%die 10,000 left, now at 3 minutes 9000 more die leaving 1000, 4min 900 die leaving 100, 5 min 90 die 10 left 6 minutes 9 die leaving 1 bacteria
Effectieness of Antimicrobial treatment depends on...
*time it takes to kill a microbial population is proportional to number of microbes. 2. microbial species and life cycle phases (eg endospores) have different susceptabilities to physical and chemical controls. 3. organic matter may interfere with heat treatments and chemical control agents. 4. longer exposure to lower heat produces same effect as shorter time at higher heat.
Autoclave psi?
auoclave at 15psi because thats twice the atmospherice pressure. *cannot autoclave plastics or powders. Normal temp:121.5 deg. C for 15 minutes *Steam must come in dirrect contact with material being steralized.
actions of microbial control agents (how other things affect w/o heat
*alternation of membrane permeability *Damage to proteins *Damage to nucleic acids
Physical Methods of microbial Growth How they are killed...
Heat, heat is very effective, fast, and cheap, Heat is frequently used to kill microorganisms. TDP TDT &DRT
TDP Thermal Death Point
lowest temperature at which all cells in a culture are killed in 10 minutes.
TDT Thermal Death Time
Time to kill all cells in a culture. **TDT and TDP are useful guidelines that indicate the severity of treatment required to kill a given population of bacteria.
DRT Decimal reduction time
Minutes to kill 90% of a population at a given temperature.
killng prions
the autoclave kills everything except prions. cows infected with prions re incinerated.
Significant number reduction (esp, spoilage and pathogenic organisms) but does not sterilize. *will not kill endospores
historical goal of Pasteuization...
destruction of M. tuberculosis. M. bovis (bovis =cow) is another form of TB that you can ger from drinking milk from a contaminated cow.
Classic holding method
63 deg. C for 30 minutes
Flash Pasteurization (HTST)
72 deg C for 15 seconds. Most common method in the US. Thermoduric organisms survive this, the thermophiles love heat.
Ultra High temperature (UHT) pasteurization
pasteurization to 140 deg C and back in less than 5 seconds. Technically not pasteurization because it sterilizes.
Bacteria that come from Milk
Listeria monocytogenos Salmonilla Coxiella brinetii (or Q fever) M. bovis Brucella species Milk is pastuerized to kill most bacteria.
Dry heat sterilization kills by oxidation...
flaming the loop incineration of carcasses -anthrax (endospores) -foot and mouth disease -bird flu Hot air sterilization -i.e. the oven cooking for 2-3 hours (equivalent is autoclave 2-3 hours vs. 15 nimutes.
Fluid Filtration with inorganic filters, organic filters diatomaceous -membranne ffiltters, cellulose acetate, pore size for bacteria is 0.2-0.4 micrometers. -Air fitration using high efficiency particulate air HEPA filters. Effective to 0.3 micrometers. **Spiroketes can get through sometimes.
Plasmolysis - when food is salted water goes out of he bacteria causing it to?
shrivel up and die
Lysteria Monocytogenes
likes cold refridgerated temps and grows there
Other ways to kill bacteria...
Low Temperrature: -slows enzymatic reactions=inhibits microbial growth -freezing fors ice crystals that damage microbial cells -refridgeration, deep freezing, lyophilization
more methods
-High pressure denatures proteins. - Desiccation prevents metabolism (dessication =drying out) -Osmotic pressure causes plasmolysis
Ionizing radiation **ionizing radiation is very high enerrgy, short wavelengths.
x-rays and gamma rays=electrons from atoms, creating highly reactive molecules and free redicals. (x-rays are dangerous bc electrons are discharged and create fre radicals. -Commonly used Cobalt-60 radioisotope -Salmonlla and Pseudomonas are particularly sensitive to radiations -setrilization of heat sensitive materials; drugs, vitamins, herbs, suture material -also used as "cold pasteurization" of food
UV light
-UV wavelength 100-400nm. (most effective around 260) -Affects NA's- Thymine Dimer formation -Actively dividing organisms are mroe sensitive because thymine dimers prevent replication -used to limit air and surface contamination; use at close range to directly exposed microorganisms.
mutation =
error in replication
why are UV lights used in surgery?
because the UV light kills most of the bacterria in the air.
Toxid =
poisin like (but you prepare it) -Toxid preparations from immunizations are best sterilized by filter method.
use dilution test
used for testing hard surface disinfectant effficacy. -metal rings are dipped in baceria, dried, and placed in disinfectant for 10 min at 20 deg. C. rings then transfered to culture media to determine whether bacteria survived treatment.
Disk-difffusion method
dick of filter paper is soaked with a chemical and placed on an inoculated agar plate; a cone of inhibition indicated effectiveness.
types of disinfectant
phenol (lister) -Modern derivatives *phenolics, bisphenols. **today phenol is toharsh to use as an antiseptic and it is used as a disinfectant. Phenols affect the plasma membrane by damaging it and the cytoplasm leaks and important stuff is lost and the cell dies.
Halogens **so reactive bc they want to complete their octet, they want one more electron.
oxidizing agents, -Iodine-antiseptic: affects protein systhesis and cell membrane. -tincture of iodine- solution with alcohol-wound antiseptic -Iodophors- combined with organic molecule for slow release of iodine- eg betadine- less iratation and does not stain skin. -Chlorine- disinfectnt: fomrs hypocholrous acid when added to h2o. NaOCL is household bleah.
Viruses are?
parasitic, completely dependant on living in the cell. they are dormant outside the cell.
soaps and detergents
emulsification leads to mechanical removal *emulsify = to get rid of **soap does not kill bacteria it just removes it like dirt.
=alcohol solution
Other types of disinfectants
Chemical food preservatives -organic acids control molds in food and cosmetics. -nitrite prevents endospore germination
Sterilant! Sporicidal in 3-10 hours, disinfectant for delicate surgical instruments **its a liquid but you can voporize it and use it in a chemiclave, which is an autoclave where chemicals are used instead of water.
Microbial Characteristics and Microbial Control. Most Resistant to Least Resistant
Prions Endospores off bacteris Mycobacteris Cycts of protozoa Vegetative protozoa Gram Negative bacteria Fungi,including most fungal spores Viruses without envelopes Gram Positive bacteria Viruses with lipid envelopes
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