exam 4 – Microbiology Answers – Flashcards

the removal/ destruction of all living organisms

(Heating is the most common way of killing microbes including thoughs with endospores

sterilization gas ethylene oxide or steam under pressure

the destruction of most microbial life on a control directed at destroyng harmful microorganisms

(Usually refers to no endosporic microbes or pathogens / uses chemicals, ultravioletradiation, boiling water or steam

the destruction of most microbial life on living tissue

(Chemicals, ultraviolet radiation, boiling water or steam are all disinfectants however some disinfectants can be antiseptics such as the same chemical however some may be to harsh for the skin

scrubbingand/or swabbingthe skin in chemicals to remove or reduce the number of microorganisms by mechanical removal

(Usually removal rather than the killin go most microbes in a limited area

a cleaning technique that _reduces or lowers__ the number of  microbes to reducecontamination and maintain safe public health levels  

(Usually accomplished by  high temp washing or washing in a sink folowed by a dip in chemical disinfectant- which are used in bars)

the permanentLOSSof reproductive capabilities (growth)

 They all mean the killing of microorganisms

(Usually with certain excepteions such as endospores

Stasis-to stop or steady

Bacteriostasis-

a chemical that preventsbacterialgrowth but does not  kill the bacteria

( Its an inhibitor and once it is removed growth might resume

Bacteria population to die at a constant rate 

(ex autoclaving)

1. Time-•the longerthe time the bacteria are exposed to the agent the the more bacteria killed
2. Agent Concentration-the higher the concentration of the agent the the faster it is to kill more bacteria /?
3. #of Microbes- the more microbes the longer it takes to eliminate the population
4. Evironmental influences- Instruments with organic debris (blood, feces, tissue, etc) will take longer to disinfect or inhibit bacteriacidal agent disinfection. ex microbes in biofilm
5.  Resistance level of microbes (endospores versus non-endospores): More time will be required to treat microbes that have high levels of resistance. For example, endospore-forming bacteria will take longer to kill than non-endospore forming bacteria.

5) Activity level of the method or agent (cidal versus static): Agents that are cidal will be more effective at reducing microbial contamination than agents that are static

1. Inner Plasma Membrane-disruption of the inner plasma membrane causes cytoplasmic contents to leak out of the bacterium why- because the plasma membrane inside cell wall transports nutrients and lets out waste interfering with growth of the cell
2. Bacterial Proteins- Enzymes are bacterial protiens/ damage to the structrue of an enzyme can inactivate them- specifically breakage of hydrogen bonds that holds the shape of the protein leading to denaturing
3. Nucleic acids-Dna and Rna that carry the bacteria cells genetic information / damage can  effect replication and transcription/ translation to create enzymes killing bacteria due to metablic functions

Logarithmically

Why- because the death rate is constant (results in a straight line

- side note- Impractical- the population of the cells would be only one hundreth of the distance between the 100,000 and the base line(3 min and 1000 cells

1. Physical Method- heat, lowtemp, Dessication, high pressure, osmotic pressure, filtration
2. Chemical Method

1. Heat
2. Low temp
3. Dessication
4. High Pressure
5. Osmotic Pressure
6. Filtration
7. Radiation

Heat

1. Thermal Death Point(tdp)-lowest temperature at which all the bacteria in a liquid suspension will be killed in 10minutes
2.  Thermal Death Time-(Tdt)   minimum length of time for all bacteria in a liquid suspension to be killed at a given temperature  
3. Decimal Reduction Time (drt)-•time (in minutes) in which 90% of a bacterial population will be killed at a given temperature
    
   

Two types of heat

1. Moist HEAT
2. Dry heat

What happens when enzymes are exposed to heat

Denaturing occurs-(breaking of hydrogen bonds that hold the shape of the protein 

Moist heat is more penatrating

More effective taht dry at a given temp or length of ex exposure/ requires equiptment (ex autoclave)

Dry heat- requires higher temps and is less penatrating requiring longer exposure/ but it is cheap and easy

1. Boiling (not reliable)- greater than 20 hrs to kill endosporer, mycobacteria, garamnegative, gram positive take 10 min to kill( vegetative bacteria/ least resistant)
2. Steam Under Pressure (Reliabl)- kills all organisms and endospores within 15 min at 15 psi 121C (time, temp, & pressure)/ sterilize culture media,solutions, medical instruments and ect withstand high temp and pressure/Retort (industrial autoclave- used in Commercial sterilization (canned foods)
3. Pasteurization- mild heating to kill food spoiling microbes without damaging the taste. - High temp short time-(HTST) pasteurization of milk involves exposure at 72°C for 15 SECONDS (no pressure) / Ultra High temp-•(UHT) involves exposure at 134°C for 1-2 sec (no pressure)- stored for several months
    
   

    

 Destroys micobes by denaturing, oxidation effects and dehydration 

( Fire burns o2)

Removal of water

without water the microbes can't grow but remain viable or dormant for years

(when the water is finally present they can resume growing)

Base of Lyophilization- freeze drying a process ued to perserve bacteria samples 

the pressure alters the protein structures

can destroy vegetative bacteria but endospores are resistant to pressure alone (temp must be added)

NO

Hypertonic environment

Prevents growth and destroy bacteria

Mold yeasts and endospores more resistant to high osmotic pressure

No

Mechanical means of removing microbes from a sample works best for bacteria, fungi, protozoa

Used to sterilize heat sensative material enzymes, vaccine, antibiotics

High efficiency particulate air (Hepa)-filters air borne microbes removing all microbes larger than .3 micrometers in diameter

Yes

Time

Temperature

Pressure

Food Industry

Commercail Sterilization- by steam under pressure in a retort

1. Washing, sort, blanch to reduce microbes which may alter color
2. cans filled to capacity
3. steam used to drive out dissolved air
4. cans sealed
5. pressurized and steamed in retort
6. cooled by water
7. Labeled stored delivered

No its not sterile - theroduric heat resistant microbes survive but are unlikely to make ppl sick or cause milk to spoil

kills microbes that cause spoilage without damaging the taste

High Temperature short time (HTST)- 72 C & 15 Sec ( no pressure)

Lower bacteria count good for refrigeration

Applied while milk is flowing through an heat exchanger

Ultra High Temperature

The milk is sprayed through a nozzle ( to perserve a non cooked taste) into an under pressure steam chamber- it is then cooled in a vacuum chamber and then packaged

1. Direct flaming or incineration
2. Hot air sterilization

Dehydration

Oxidation Effect

No can't be used for sterilization

Slow microbe growth

Does not kill the microbe

1. Ionizing- shorter wavelength higher energy-Gamma rays (penatrates deeply)x rays are similar- Ionization of water- the ionized particles pass through vital portions of the cell causing mutation to kill the cell
2. Nonionizing- longer wavelength less energy- ultraviolet light or rays- damges exposed cells combing or bonding  adjacent pyrimidine bases to thymines

Uv light damages Dna of exposed cell causing bonds to form between pyrimidine base and thymine

Disadvantage- not very penatrable

damage human eyes

long exposure can cause burs and skin cancer in humans

1. What organisms the disinfectant effects
2. The concentreation of disinfectant-( it can effect the action of the disinfectant
3. Nature of material being disinfected- ex organic mater might interfere with action
4. Ph of medium for greater effect on activity
5. will the disinfectant easiy make contact with the microbe
6. how long the disinfectant needs to be left on a surface

1. Use- Dilution Test- Glass cylinders or metal is dipped into bacteria, removed, and dried at 37 C . Then they are placed in a concentration of disinfectant recommended by the manufacturer and left for 10 min ar 20 c. Then they are transfered to medium that permits bacteria growth or sterile broth which are incubated. Effectiveness determined by how much bacteria grows
2. Disk diffusion- soked disks are placed on a agar plate filled with bacteria. they are then incubated and a zone of clearing indicated disinfectant effectivness

Chlorine

Iodine

Hypochlorous Acid (Bleach)

oxidizing agent that make the compound loose electrons and disrupts the enzyme functioning

Effectiveness of bleach against endospores is fair

used in disinfectining drinking water, pools, household items and utensils

Chlorine

Specifically Chlorine dioxide

Oxidizing agent that inhibits protein and enzyme functioning

- Speciffically impairs protien synthesis and cell membrane by creating complex amino acids and unsatruated faty acids

Effectiveness agains endospores is POOR

Tincture-(mixed with alcohol)used in the past as antiseptic/ likely irritates skin and prone to stain/ used for disinfecting water when camping

Iodophors-(mixed with organic molecule) does not stain and less irritating to skin/ commonly used for medical antisepsis/ used to prepare skin for surgery and surgical hand scrubbing

MORE LIKELY TO BE USED IN HOSPITALS 

Dr. Joseph Lister

Phenol (carbolic acid) to control surgical infections in the operating room

Carblic Acid- a toxic acid

Denatures enzymes and disrupts or injures lipid containing plasma membrane resulting in leakage of cellular content.

Phenol is not used  due to foul ordor and irritating skin

Derivatives of phenol

Destroy microbes by denaturing enzymes and disrupting the plasma membrane causing leakage

Effectivness against endospores POOR

Lysol- uses active phenol ingrediant

Derivatives of phenol  containing two phenolic groups

Destroys by triclosan inhibiting enzymes need to create fatty acid lipids for plasma membrane

Effectivness against endospore INEFECTIVE