Chapter 9: Control of Microbial Growth- Part 1 Flashcards
The British Medical Journal stated that British physician ______ _____ “saved more lives by the introduction of his system than all the wars of the 19th century together had sacrificed”
Joseph Lister
Lister revolutionized _______ by…..
Surgery
Introducing methods to prevent infection of wounds
Whose work was Joseph Lister inspired by and what did it lead him to wonder?
Pasteur (swan-neck flasks), wondered if “minute organisms” might be responsible for infections
What did Lister apply directly onto damaged tissues?
Carbolic acid (phenol), helped prevent infections
Lister improved methods further by…
Sterilizing instruments and maintaining clean operating environment
Lister introduced..
Antiseptics
Until the ___ century, patients undergoing even minor surgeries were at great risk of developing…
19th
Fatal infections
Why did people often die from infections after surgery before the 19th century?
- Physicians did not know their hands could pass diseases from one patient to the next
- Did not understand airborne microbes could infect open wounds
Why can dental surgery be dangerous (example)?
Some of the normal flora in the mouth can move with dental surgery and cause infection in the heart
Two types of approaches to control microbial growth
Physical methods
Chemical methods
Physical methods of controlling microbial growth
Heat
Irradiation
Filtration
Mechanical (e.g., washing)
Chemical methods of controlling microbial growth
Disinfectants
Antibiotics
Sterilization
Removing all microbes, “best of the best”
Pasteurization
Heat treatment
Decontamination
Reduce number of microbes to “safe” level (Wescodyne)
Sanitation
Substantially reduce microbe number public health standards (usually what is done in bathrooms)
Preservation
Delaying spoilage (usually in terms of food biology)
Disinfectants
Used on inanimate objects (fomites)
-Will eliminate most microorganisms
Ex: ammonia, bleach, pines, Lysol
Antiseptics
Chemicals applied to body surfaces to help control infection
Ex: iodine, rubbing alcohol, mercurochrome
Why is hydrogen peroxide a poor antiseptic?
Our skin has an enzyme called catalase which inactivates the hydrogen peroxide (bubbling means it is not working)
Microbial control method depends on what?
Situation and level of control required
Places where microbial control is practiced
Daily life, hospitals, microbiology laboratories, food production facilities, water treatment facilities
Why don’t we entirely sterilize water?
Some bacteria are helping to clean our water waste and are necessary (which is why you should not put sterilizers down the toilet)
Selection of an antimicrobial procedure would look at… (5)
- Type of microorganism
- Number of microbes initially present
- Environmental conditions
- Potential risk of infection
- Composition of the item
Type of microorganism
- Heat and chemical resistant
- Bacterial endospores and myobacterium species
- Vegetative cells are susceptible to most disinfectants
Number of microbes initially present
“99.9% effective” would still be a lot of bacteria! (Lysol)
Environmental conditions
Oil, grease and dirt can potentially inactivate products
Critical instruments (Potential risk of infection)
Sharps
Semicritical instruments
Mucous membranes
Noncritical instruments
Intact skin
Composition of item
- Metals are damaged by some disinfectants
- Plastics are damaged by irradiation
The most common method of sterilization of sharps is..
Irradiation or autoclave
Moist heat techniques
Boiling
Pasteurization
Autoclave
Commercial canning process
Boiling kills….
Most bacteria and viruses
What is the goal of pasteurization?
Kill as many microorganisms as possible without changing the taste, texture, etc of the food
What is pasteurization effective for?
Many food-borne microbes
Process of Pasteurization
Heat to 72 degrees C for 15 seconds for most liquids
Autoclave
Huge pressure cooker, high pressure increases boiling temp of water, typically reach 120 decrees celsius at 15 psi
What type of virus would be most likely to survive the high temperatures?
Non-enveloped
The most serious threat in the commercial canning process is…
Clostridium botulinum endospores because they are anaerobic, but when placed in a can they germinate and produce endospores
What do canning facilities use?
Retorts which are large autoclaves
What do retorts do?
Prevent endospores from germinating inside the can, thus preventing botulism toxin production
In the commercial canning process, how do we know the retorts have worked?
A “dummy can” that has a monitor on the inside is included with every batch
Dry heat
Heating items to 200 degrees celsius or more
You have used Wecodyne on a paper towel on your laboratory bench and have removed most of the microorganisms from it making it “safe”. You would say that it has been
Decontaminated
Chlorine bleach is an example of a(n)
Disinfectant
