E2L14: Physical Methods: Not Heat Flashcards
What’s the MOA for scrubbing, filtration, and sedimentation? Disinfect/sterilize?
Mechanical, disinfect
Why do you need a surfactant for handscrubbing?
- surfactant lowers surface tension (ex: soap)
- it acts as a surface acting agent
- emulsifies dirt and allows it to be washed off easily
What 2 kinds of soap can you use for handscrubbing?
- non-germicidal (aka “bland soap”)
- germicidal (triclosan or alcohol-based)
Define “bland soap”.
- just soap, no germicidal chemical
- nothing is killed
- just disinfectant
What is residual action?
- property exhibited by a chemical
- it stays on to kill off more bacteria
Talk about triclosan-based germicidal soap.
- phenol-type cmpd
- has residual action
- -> even though H2O+dirt off already, triclosan remains on skin still and continues to act as a germicide
Talk about alcohol-based germicidal soap.
- ex: alcohol hand wipes (~62% alcohol)
- NO RESIDUAL ACTION (evap. quickly)
- good for times w/o visible soil on hands
Which has residual action? Triclosan-based germicidal soap or alcohol-based germicidal soap?
- triclosan-based!
- (alcohol-based evaporates too quickly to have a lasting effect)
What is filtration?
- putting a liquid or gas thru a screen/porous material to remove things not in solution, such as large particles
- used to treat H2O
- might use rocks/sand (e.g. pools) to remove larger particles
What are the 4 different pore sizes of membrane filtration?
- 0.45 micrometers
- 0.2 micrometers
- 0.02 micrometers
- 0.01 micrometers
What are membrane filters made out of? What do they kinda look like?
- made of cellulose
- look like ##### (like a screen) #️⃣
What does a 0.45 micrometer membrane filter screen out? What can still get thru?
- -> removes all eukary (e.g. yeast/mold) + large prokary (ex: E. coli, Staph aureus)
- -> mycoplasma still gets thru
What does a 0.2 micrometer membrane filter screen out? What can still get thru?
- -> “sterilizes”
- -> removes all prokary, including mycoplasma
- -> viruses (DNA/protein coat), viroid (nucleic acid), prions (amino acids) can get thru
What does a 0.02 micrometer membrane filter screen out? What can still get thru?
- -> removes viruses
- -> prions still let thru
What’s the problem with membrane filters with smaller holes?
The smaller holes get clogged easily.
What does a 0.01 micrometer membrane filter screen out? What can still get thru?
- -> removes everything that the prev. sized pores remove
- -> PRIONS ARE STILL THERE
- -> prions = 5nm
- -> 0.01 micrometers = 10 nm, 10nm>5nm
With 0.2 membrane filtration, will you be able to filter out yeast?
YES, b/c it’s a eukaryote.
0.45 micrometer filters screen eukaryotes out already
Describe sedimentation.
- let H2O sit, so that colloids (suspended particles, inclu. bacteria) can settle to bottom
- 1st step of water purification
What are the steps done in water purification?
1) sedimentation: have holding tank outside your house, stuff settles @ bottom, can add FERRIC SULFATE to help settle, can add ENZYMES to digest some particles
2) filtration: soil/gravel filters out smaller stuff
3) add chlorine
In water purification, what % of microorg is removed in the 1st 2 steps (sedimentation+filtration)?
90-95% of all microorg
Define “desiccation”. Does it disinfect or sterilize?
= “drying”
- -> you’re removing the H2O necessary for enzymatic hydrolysis
- -> disinfects
How sensitive are the following organisms/things to desiccation? (Syphilis, gonorrhea, e. coli/staph/salmonella)
- syphilis –> v sensitive, few minutes
- gonorrhea –> 1 hr to a few hrs
- E. coli/staph/salmonella –> 2-3 months (b/c capsules/slime layers)
How sensitive are the following organisms/things to desiccation? (TB, spores, HIV/AIDS, Hep B)
- TB –> 8 months
- spores –> INDEFINITELY
- HIV/AIDS –> 6hrs (outside cell), 1.5 days (inside cell)
- Hep B –> at least 1 week
What are some uses of desiccation?
1) it’s nature’s way of cleaning the environment
2) food preservation –> but not sterile!!! (egg/cereal)
3) drying drugs
4) infections (yeast), best to keep dry
5) spreading infectious org (dry > wet sponge)
How long to antibiotics last while dry? How long if they’re wet?
dry, months; wet, 2-3 weeks, but typ. 10-14 days
Young children + tight clothes = …
Trapped moisture + Candida infection
Keep your kids dry!!!
Which is better? Keeping the area dry or using fungal cream (nystatin)?
Better to keep DRY, even w/ athlete’s foot.
Are cold temperatures CIDAL to bacteria?
NO, not cidal; bacteria are prokaryotes and can “the cold never bothered [them] anyway”
–> disinfects
Refrigerator MOA? Disinfect/Sterilize?
- slowing enzymatic hydrolysis (slows)
- kept at 4C, just above freezing
- -> disinfect
Freezer MOA? Disinfect/Sterilize?
- removing H2O for enzymatic hydrolysis (stops)
- kept at 0C
- -> disinfect
Osmotic Pressure MOA? Disinfect/Sterilize?
Plasmolysis!!! (use hyperosmotic soln)
- -> disinfect
- -> (NOT PLASMOPTYSIS)
In order to cause plasmolysis, you need a hyperosmotic soln. What can use use to create such a soln?
- brine (~30% salt)
- high sugar (50-60% sugar - jelly)
What are some organisms that can w/stand high salt and high sugar?
- halophils –> able to grow in up to 36% salt, not patho
- saccharophils (fungi) –> up to 70% sugar
For example, what is the MOA being used in order to control the growth of microorg on minced meat pie?
Plasmolysis (osmotic pressure) b/c of high sugar content
How long should you be out in the sun w/o protection?
Only 15 minutes
Sunlight MOA? Disinfect/Sterilize?
Photo oxidation
- similar to incinerator/hot air oven (protein oxidation)
- heat which destroys enzymes
- -> disinfects
Why is sunlight’s MOA not UV radiation?
Some bacteria will get mutations from the UV light (of the sun), but the UV light isn’t strong enough to control bacteria.
How long would it take sunlight to kill TB?
Hours
Name all of the different types of radiation discussed in this lecture.
UV, Infra-red/Microwave, Gamma, Cathode, X-ray
How long is UV light? Hyperactive ions? MOA? Disinfect/Sterilize? Good/bad penetration?
- b/t 100-400nm (visible light is 400-700nm)
- no hyperactive ions
- MOA = pyrimidine dimers
- disinfects
- poor penetration (sunscreen helps!)
Explain pyrimidine dimers.
- pyrimidines = thymine/cytosine
- dimer = UV + 2 thymines+cytosines; also a mutation
- if mutations enough, will cause DEATH
Why does UV light have such poor penetration?
oil, dirt, paper, shadows prevent UV from being a sterilant, which is why sun screen will protect you
Describe UV light as a disinfectant in air quality.
w/ the use of laminar flow hoods (UV lamp disinfects air, fan blows cleaner air out)
Can you use UV light for water purification?
Not alone, not good for getting rid of protozoan cysts (ex: Giardia/”Beaver Fever”)
- -> better to FILTER 1st (remove cysts)
- -> THEN UV light for further purification
- -> charcoal filters of 0.8 micrometers will get rid Giardia
Infra-red/Microwave wavelength? MOA? Disinfect/Sterilize?
- longer than both UV/visible light
- MOA (if wet) –> protein coag
- MOA (if dry) –> protein oxidation
What are some things that you can disinfect with Microwaves?
- plastic contact lenses
- urinary catheters (important, b/c UTIs common if reuse)
- milk
What’s the MOA for gamma/cathode/x-rays?
Hyperactive ions!!!
- -> they’re all ionization radiation
- -> their wavelengths short+powerful enough to produce hyperactive ions
- -> can cause mutations
- -> large amts radation -> death ; destroys DNA
What does it mean if the FDA “cleared” something? If the FDA “approved” something?
- “cleared” (cleared for use, not necessarily effective)
- “approved” (effective)
How are gamma rays produced?
- can be produced from atomic/hydrogen bombs
- radioactive isotopes (ex: Cobalt 60)
Do gamma rays disinfect or sterilize?
Depends on the range used:
1) low - nothing much (ineffective, p much)
2) medium - disinfects; get longer shelf life, use less salts in veggies/bacon
3) high - sterilizing (NOT FDA CLEARED NOR APPROVED)
Which of the follow is used to “sterilize” (remove all prokary) heat labile soln?
a) incineration
b) autoclave
c) membrane filtration
d) boiling water
e) pasteurization
c) membrane filtration
