14 Control of Microbes in the Environment (Midterm 2 up to here) Flashcards
Controlling microbes in the envir means…
a. ctrling microbes on surfaces
b. ctrling microbes inside an infected host
c. All of the above
a. ctrling microbes on surfaces
When talking about ctrling microbes, what can “control” mean? (3)
- KILLING of microbes on a surface
- Physical REMOVAL of microbes from a surface
- PREVENTING AN INCREASE in microbial numbers on a surface
T or F: Ctrling microbes means creating a sterile envir.
F
Not necessarily. It CAN also mean just reducing their numbers
What two types of methods are used for ctrling environmental microorganisms?
- Physical methods
2. Chemical methods
List three physical methods by which microbes can be ctrled.
- Heat
- Radiation
- Filtration
List three chemical methods by which microbes can be ctrled
- Antiseptics
- Disinfectants
- Preservatives
What does heat do to microbes? (3)
- Denatures proteins
- Denatures DNA
- Melts lipids
–>Cell death
What kind of heat is best to use? Why?
Moist heat (not dry heat)
a. faster heat penetration
b. better protein denaturation (H2O helps disrupt chemical bonds)
What’re two advantages of using heat to ctrl microbes?
- Economical
2. Easy to ctrl and monitor
Give 4 examples of how heat can be used to ctrl microbe populations. Also, indicate what gets killed via each method.
- Boiling water (bacteria and viruses get killed; spores DO NOT get killed)
- Pressurized steam (via the autoclave) (sterility - everything gets killed)
- Pasteurization (does not kill all bacteria, does not kill spores)
- Commercial canning (everything but a few spores remain)
What’re two ways you can tell something has been autoclaved?
- Heat-sensitive autoclave TAPE changes colour
2. INDICATOR strips on autoclave pouches
What’re 4 good habits to have when handling autoclaved materials?
- Check package integrity
- Check expiry date
- Check indicator strip
- Treat inside of package as sterile; the outside as not
How can you ensure that your autoclave is working properly (i.e. killing everything)?
Use a “Spore Strip” test to test whether the autoclave is killing spores or not. If so, then it’s working (since spores are hardest to kill). If not, the the autoclave isn’t working properly.
What is pasteurization?
When MILD heat is used to REDUCE the number of bacteria
T or F: Pasteurization kills all bacteria, but not spores.
F
It doesn’t kill all the bacteria present, nor does it kill spores.
What temperature and time was utilized in Pasteur’s original method of pasteurization?
63ºC, 30 mins
What method of pasteurization is used today? Describe it.
HTST (High Temp, Short Time)
72ºC, 15 sec, followed by rapid cool down > less adverse effect on taste vs. Pasteur’s original method
What’s a less frequently-used method of pasteurization (in Can/USA, at least)? Describe it. What’s a disadvantage of it?
UHT (Ultra-High Temperature) treatment
140ºC for 2 seconds > get 6-9 mths of room temperature shelf life,
Disadvantage: Milk has a “cooked” flavour
What is commercial canning?
A form of heating that uses special conditions of time and temp so that both spoilage organisms AND spores are killed
How many spores is commercial canning expected to kill?
10^12 spores = high safety margin
What types of foods require less heating time and lower heating temps wrt commercial canning?
- Acidic foods
- High salt foods
- ->Bacteria are more sensitive in these envirs
What types of foods require more heating time and high heating temps wrt commercial canning?
- High protein foods
- High fat foods
- -> Bacteria are more protected in these envirs
UHT treatment and commercial canning methods produce foods that’re commercially sterile. Differentiate b/w commercially sterile and true sterility.
True sterility involves the complete destruction of ALL microbes.
Commercial sterility is when food microbes/spores that can grow at storage temps are killed > prevents them from growing during storage and distribution
List three physical methods by which microbes can be ctrled.
- Heat
- Radiation
- Filtration
List two types of radiation that can be used to ctrl microbial growth:
- Ultraviolet Light
2. Ionizing radiation
Germicidal lamps are a type of…
ultraviolet light
How does UV light (“germicidal lamps”) stop replication in microbes and cause mutations?
By causing DNA bases to “cross-link”
About how long do microbes need to be exposed to UV light before they can be killed?
5-45 seconds
What’re 3 disadvantages of using UV light to ctrl microbial growth?
- Not ALL microbes are equally sensitive to UV light
- UV light damages the body (skin, eyes, etc.)
- UV light does not penetrate through liquids, plastics, glass, etc.
UV light is useful for ____ and ____ sterilization only.
surface, air
What does ionizing radiation do?
It dislodges electrons from atoms, disrupts chemical bonds, and breaks DNA
B/w UV radiation and ionizing radiation, which one has higher penetrative power?
Ionizing radiation
Another term for “ionizing radiation” when applied to commercial uses is…
“cold sterilization”
If a food is heat-sensitive, what can be used to sterilize it?
Ionizing radiation (“cold sterilization”)
[Can’t use any heating methods due to being heat sensitive]
T or F: Putting a dry object into a microwave will sterilize it.
F
How do microwaves heat up objects?
They excite WATER molecules, which then release energy as heat
Can microwaves be used to kill microbes?
Yes, but only via heat, not the waves themselves (and the presence of water is req’d)
T or F: The longer wavelengths of microwaves are better suited to kill microbes compared to UV rays.
F
Long wavelengths radiation cannot kill microbes since they’re low energy
List three physical methods by which microbes can be ctrled.
- Heat
- Radiation
- Filtration
This method of microbial ctrl is used to physically remove microbes w/o killing them.
Filtration
What’re membrane filters?
Cellulose fiber w/ pores that range in size from 0.2 μm to 0.5 μm.
Can membrane filters trap bacteria?
Yes
Can membrane filters trap fungi?
Yes
Can membrane filters trap viruses?
No
When are filters usually used to ctrl microbes?
When we’re dealing w/ heat sensitive-liquids or gases
List three chemical methods by which microbes can be ctrled
- Antiseptics
- Disinfectants
[Note: 1. and 2. are collectively known as “Germicides”] - Preservatives
Out of the three chemical methods by which microbes can be ctrled, which ones are used to KILL microbes on surfaces?
- Antiseptics
2. Disinfectants
Out of the three chemical methods by which microbes can be ctrled, which ones are used to inhibit the growth of microbes?
- Preservatives
Why or why aren’t germicides and preservatives equivalent to antibiotics?
Germicides and preservatives are not SELECTIVELY TOXIC to specific types of microbes.
What type of germicide is used on biological surfaces?
Antiseptics
What type of germicide is used on inanimate surfaces?
Disinfectants
3 possible germicidal mechanisms of action:
- Denaturing and coagulating cellular proteins
- Dissolving lipids (e.g. in cell membranes)
- Oxidizing cellular macromolecules
- What are germicides always going to do for sure?
2. What CAN germicides do, but not always?
- Greatly reduce # of microbes on a surface (always)
2. Create a truly sterile surface (s. times; depends on agent)
What factors affect how well germicides will work? (5)
- Length of exposure
- Temp of envir
- Conc of germicide
- Presence of organic matter
- Number/type/special characteristics of microbes present
What kind of temperatures are germicides more effective in?
Higher temps
T or F: All microbes are killed at the same rate when germicides are used.
F (hence, time of exposure to germicides differ depending on the microbes being killed)
Higher concs of germicide is more effective at killing microbes. But what’s the downside?
Higher concs = More toxic effects (potentially)
T or F: Bacteria that grow as biofilms are more resistant to germicides compared to the same bacteria as free cells.
T
Because the presence of organic matter reduce germicide effectiveness, what “Golden Rule” should be followed?
“Clean before disinfecting”
Germicides are rated according to ______.
potency
List the levels of germicides.
- High-level (“sterilants)
- Intermediate-level
- Low-level
What do high-level germicides kill?
All microbes + spores
What do intermediate-level germicides kill?
All microbes (not spores)
What do low-level germicides kill?
Most vegetative bacteria (NOT Mycobacteria, spores, or some viruses)
Why are the most potent germicides only used as disinfectants?
Bc they’re usually the most toxic to biological surfaces
List the 3 risk categories of some medical devices (The Spaulding Classification System)
- Critical
- Semi-critical
- Non-critical
What kind of medical items are considered “critical” when it comes to microbial ctrl?
Items that contact blood stream or sterile body tissues
What kind of medical items are considered “semi-critical” when it comes to microbial ctrl?
Items that contact mucous membranes
What kind of medical items are considered “non-critical” when it comes to microbial ctrl?
Items that only contact intact skin
Needles would fall under which risk category?
Critical
Stethoscopes would fall under which risk category?
Non-critical
Mouthpieces would fall under which risk category?
Semi-critical
Out of the three risk categories of some medical devices, which one would req higher potency germicidal agents?
Critical
T or F: Skin can be sterilized after using soap for 5 minutes.
F
Skin cannot be truly sterilized.
What’s the best way to prevent harmful microbes from getting on a physician’s hands?
Use a physical barrier (a rubber glove)
List 8 categories of germicidal agents.
- Phenols
- Alcohols
- Peroxides
- Heavy metals
- Halogens
- Chlorhexidine
- Quaternary ammonium
compounds (“Quats”) - Alkylating agents
Lister used WHAT as a germicide on the skin?
Carbolic acid (basically a phenol molecule)
At higher concs, what side effects do phenols cause? (2)
- Skin irritation
2. Neurotoxicity
What’re phenols used as today?
a. antiseptics
b. disinfectants
b. disinfectants (germicides for inanimate surfaces)
Triclosan is an example of…
a chlorinated phenol
What is triclosan’s MOA?
inhibits an enzyme needed for bacterial fatty acid synthesis
The use of triclosan in WHAT was banned by the FDA?
antibacterial soaps
What is the MOA of alcohols (in germicides)?
- Dissolves lipids
2. Denatures proteins
What’re alcohol germicides effective against?
Bacteria, viruses, fungi
What AREN’T alcohol germicides effective against?
Spores
What’re alcohols used as?
a. antiseptics
b. disinfectants
a. antiseptics (alcohols are non-toxic and non-irritating)
Why are alcohol germicides usually used as 70% solns in water? (2)
- Water aids in protein denaturing effect
2. Water slows the rate of alcohol evaporation
What’s the most commonly used germicide for hand sanitation in healthcare?
Alcohols
Bacteria located in ____ may survive after alcohol evaporates from the skin.
pores
What kind of microbes are killed by peroxide germicides (such as H2O2)?
Anaerobic bacteria
PerCept (R) is an example of…?
“Accelerated hydrogen peroxide”
List 8 categories of germicidal agents.
- Phenols
- Alcohols
- Peroxides
- Heavy metals
- Halogens
- Chlorhexidine
- Quaternary ammonium
compounds (“Quats”) - Alkylating agents
What’s the MOA of heavy metals when used as germicides?
They bind strongly to cellular proteins > inactivates cellular enzymes and inhibits membrane fns
At low concs, heavy metals are used as…
a. antiseptics
b. disinfectants
a. antiseptics
Fungal infections are usually treated w/ this heavy metal.
Selenium
Mouthwashes usually contain this heavy metal for antiseptic purposes.
Zinc
Burn wound ointments often contain this heavy metal.
Silver
Heavy metals can be used on these types of surfaces to control microbial growth.
“Touch surfaces” (surfaces, such as light switches or grab bars, that’re constantly touched)
MOA of halogens when used as germicides?
Denatures proteins
Two most popular halogens used as germicides?
- Chlorine
2. Iodine
Chlorine is mostly used in…
a. antiseptics
b. disinfectants
b. disinfectants
What product includes chlorine in the form of sodium hypochlorite?
Household bleach (Javex)
What concentration of chlorine is often used to treat drinking water?
0.5-1.0 ppm
Disadvantages of using chlorine as a germicide? (2)
- Inactivated by organic matter
2. Poor long term stability
Iodine is often useful as…
a. an antiseptic
b. a disinfectant
a. an antiseptic
Name two types of germicidal preparations that iodine is often part of? What is each composed of?
- Tincture (2% iodine + 70% alcohol)
2. Iodophore (iodine + a hydrocarbon carrier)
What’s the advantage of tinctures (2% iodine + 70% alcohol)?
Combined effect of TWO antiseptics
What’s the point of the hydrocarbon carrier in iodophores (iodine + a hydrocarbon carrier)?
The carrier slows and prolongs the release of iodine
Betadine (TM) is an example of what?
An iodophore (iodine + polyvinylpyrrolidone, a hydrocarbon carrier)
MOA of chlorhexidine (germicide)?
- Disrupts membranes
2. Denatures proteins
Chlorhexidine is used as…
a. an antiseptic
b. a disinfectant
a. an antiseptic
This germicide is one of three antiseptics on the “WHO Essential Medicines List”
Chlorhexidine
What is chlorhexidine usually used for? (2)
- Coating catheters and implanted devices, etc.
2. Antiseptic skin creams and wipes
MOA of quaternary ammonium cmpnds (“Quats”)?
Dissolves lipids in cell membranes
What are quaternary ammonium cmpnds?
Detergents made of 4 organic gps attached to a nitrogen atom
Quaternary ammonium cmpnds have good activity against everything except these.
- Mycobacteria
2. Spores
Name one product in which Quats are used.
Antiseptic mouthwashes
MOA of alkylating agent germicides?
Cross-links and denatures cellular macromolecules
Alkylating agents are used as…
a. antiseptics
b. disinfectants
b. disinfectants
If given long exposure times (5-10 hours), alkylating agents can act as what?
High-level germicides (sterilants)
Name a liquid type of alkylating agent.
Glutaraldehyde
Name two gaseous types of alkylating agents.
- Ethylene oxide
2. Propylene oxide
Advantage of glutaraldehyde?
It has good action in the presence of organic material
How long does it take for glutaraldehyde to kill vegetative bacteria?
10 mins
How long does it take for glutaraldehyde to kill spores?
10 hours
What’s the advantage of using gaseous alkylating agents, such as ethylene oxide or propylene oxide?
They allow for penetration of alkylating agent into hard-to-reach areas
What’re three disadvantages of using gaseous alkylating agents (e.g. ethylene or propylene oxide)?
- Very toxic
- Explosive
- Carcinogenic
Germicide “failure” is often due to… (4)
- not following proper procedures and manufacturer instructions
- inadequate cleaning (i.e. failing to remove organic material first)
- Wrong agent for situation
- Germicidal product itself is contaminated
T or F: Germicides can be used as a substitute for proper preventative procedures.
F
Germicidal chemicals play an important role in maintaining a safe working environment when used _____ and _____.
regularly, properly
The antibacterial products available to consumers usually have _____ antibacterial properties.
Why?
modest/low
To avoid toxicity
What determines whether or not antimicrobial consumer products are beneficial?
If they are safer and more effective than regular soap and water
T or F: If germicidal chemicals are shown to kill microbes in the lab, then this means that they can reduce the spread of infectious disease in real-life (compared to non-germicides)
F
A product is considered to be microbiologically “spoiled” if…(3)
- Microbes w/ pathogenic potential are present
- Toxic microbial metabolites (e.g. LPS) are present
- Microbial growth has caused deterioration of the product
What is the main requirement for chemicals that’re to be used as preservatives?
What’re 2 other requirements for preservatives?
- They must be completely NON-TOXIC after repeated contact and/or ingestion
- No interactions w/ other product ingredients
- Effective against wide range of microbes
Preservatives can either…
- kill microbes directly
2. alter the envir so that microbes can’t grow (more common)
What’re the most common preservatives used in pharmaceuticals?
Standard germicidal chemicals at LOW CONC
Preservatives used in foods must be classified by the US FDA as…
GRAS
Generally Recognized As Safe (i.e. not toxic after ingestion)
What is the MOA of organic acids when they’re used as preservatives in foods? (2)
- They interfere w/ proper fn’ing of cell membranes
2. They create an acidic envir which inhibits growth
What is the MOA of sodium nitrite when used as preservatives in foods?
Inhibits growth of Clostridium > reduces risk of botulism due to C. botulinum
What is the MOA of high sugar/salt when used as preservatives in foods?
Reduces water availability
Name three spices/herbs that have a strong antimicrobial effect.
- Cinnamon
- Cloves
- Mustard
Name three spices/herbs that have a medium antimicrobial effect.
- Coriander
- Cumin
- Thyme
Name three spices that have a weak antimicrobial effect.
- Black pepper
- Red pepper
- Ginger
What spice has been found to be effective in vitro against hospital-associated strains of Clostridium difficile?
Tumeric
Name 2 types of “biological” control agents that are used as food preservatives.
- Bacteriophage
2. Bacteriocins
What’re bacteriocins?
Small peptides made by some bacteria that KILL OTHER BACTERIA by forming holes in plasma membranes
What’s the ONLY bacteriocin approved as a food preservative? What bacteria is it toxic to?
Nisin
It’s toxic to Clostridium botulinum and some other Gram positive bacteria
In “Modified-Atmosphere Packaging” of foods, what is normal air replaced with to prevent aerobe growth?
Nitrogen/CO2 mixture
In “Modified-Atmosphere Packaging” of foods, what is normal air replaced with to prevent anaerobe growth?
90% O2 + 10% nitrogen mixture
