Lecture 6: Controls of Microbial growth Flashcards
Sterilization
• The killing or removal of all viable organisms within a growth medium
ABSOLUTE DESTRUCTION OF EVERTHING! - pathogenic or non-path, all virus, & ENDOSPORES)
Inhibition
• Effectively LIMITING microbial GROWTH
- NOT able to complete binary fission & NOT able to increase cell #
• NO killing taking place
ORGANISM IS NOT BEING KILLED/PERSISTS
If we’re describing an antibiotic that’s being used inside of a person’s body & that antibiotic is deemed bacterioSTATIC, what are you also relying on in this ex?
HAVE TO HAVE AN IMMUNE SYSTEM - b/c if they don’t & they finish their 5-day course of antibiotic, as soon as that antibiotic drops in concentration in their blood for good, those ORGANISMS are STILL THERE, they’re JUST BEEN GROWTH ARRESTED (gonna start doing binary fission & increase their # again)
- so you cannot give a bacteriostatic drug to a patient who’s just had a bone marrow transplant & is in immunosuppressant therapy
- you can’t give a bacteriostatic drug to a patient that has AIDS & doesn’t have much of an adaptive immune system to work with
need to consider you patient in order to understand the type of therapy that’ll make the most sense - sometimes if the immune systems not there, you need to do the killing by actually using the organism all together
Decontamination
• The treatment of an object to make it safe to handle (SAFETY)
= SANITIZE
- removing organisms in MASS - but NOT killing specific ones, NOT making sure all gone, just trying to DECREASE THE #’s (make sure nutrients are gone or any organism that might’ve been contaminating will have a good chance of being removed so there’s fewer left behind at the end)
- outcome: benefit to person
ex: wash dishes, wash hands
Disinfection
• Directly targets the REMOVAL OF ALL PATHOGENS (cause disease)
- organisms that have the capacity to cause the disease are the ones that’ll be eliminated in their entirety & then the organisms that are left behind are at the v. least non-path & not worrisome
- ex: pasteurization - eliminating path. from milk or apple juice for ex & then eliminating some other ones as well, so when milk gets to shelf it has the capacity to last long (extend shelf-life & making sure organisms capable of disease are gonna be eliminated)
• Not necessarily all microorganisms
Heat Sterilization
• HIGH TEMPERATURES DENATURE MACROMOLECULES
- breaks low energy bonds (VdW’s, ionic & H-bonds) that were holding the folded conformation of protein together)
- change in shape renders the molecule non-functional (think: key had shape change)
- DNA gets denatured b/c H-bonds are v. weak & easy to break that hold them together
- ds DNA characteristics genome of living organisms so you anticipate that’ll break & denature
- & VdW’s ints. & f.a tails - PM integrity (PM structure will also be disturbed as a result of heat treatment)
DECIMAL REDUCTION TIME (D)
• Amount of time required to reduce viability tenfold (get efforts your looking for) is called the DECIMAL REDUCTION TIME (D)
- Time it takes for a 10 fold reduction in bacterial numbers
ex: 100 bacteria ten fold will be 10
Pasteurization:
is the process of using precisely CONTROLLED HEAT to REDUCE the MICROBIAL LOAD IN HEAT-SENSITIVE LIQUIDS
(process used to take something that is technically heat sensitive to a certain degree & eliminate disease causing organisms & reduce counts of organisms overall so SHELF LIFE of the material will be EXTENDED so someone profits from that & we meet needs of society (eat or drink)
Pasteurization does…
NOT kill all organisms -> not sterilization (DISINFECTION)
- always organisms in this case, even if you haven’t opened sealed carton - means pasteurization process wasn’t sterilization but rather was called DISINFECTION - make sure disease causing organisms are eliminated & total counts are reduced, but organisms are still present
In the case of milk many different time and temperature combinations can be used…In the case of milk many different time and temperature combinations can be used…
(balance temp/time make sure material is still desired/want to consume)
- LTLT (low-temperature/long-time)
- 63oC for 30 MINUTES
• HTST (high-temperature/short-time)
• 72oC for 15 SECONDS (more than 30 fold reduced)
* - desired b/c it reduces exposure time to the point where you can process so much more - EFFICIENCY (time is money)
Which is desired?
- LTLT (low-temperature/long-time)
- 63oC for 30 minutes
OR
- HTST (high-temperature/short-time)
- 72oC for 15 seconds
HTST is desired b/c it reduces exposure time to the point where you can process so much more - efficiency (time is money)
kill Coxiella burnetii, the causative agent of Q fever (disease), which is the most heat resistant pathogen found in milk
The Autoclave
The autoclave is a sealed device that uses steam under pressure
Allows temperature of water to get ABOVE 100oC (which normally would be vapourization point)
121oC for 15 min at 15 pounds per square inch of pressure is typically used
To ensure sterility this means that the point that takes the longest to heat must stay at 121 for 15 min
What is the reason for how the autoclave “Allows temperature of water to get above 100oC”? As it normally would be the vapourization point
reason: COMBINE IT WITH PRESSURE
- forces water molecule which will normally have H-bonds broken @ 100oC to stay proximal to 1 another so you continuously have H-bonds formed to keep it in a liq state
- 3.4 on average per water molecule is what you expect in liq state, zero H-bonds per molecule in the vapourized state
- therefore, forcing H-bonds to stay, maintaining liq state & moist heat is v. effective at transferring that heat to cooler objects its in contact with (opposite of dry heat)
The Autoclave is #1 for…
TRUE STERILIZATION
- EVERYTHING is GONE: endospores, viruses (no longer infectious), bacteria (path & non-path)
- complete destruction of any life form, either DORMANT OR NOT
