Topic 11 Flashcards
What is disinfecting used for?
Body surfaces and objects that don’t need to be completely sterile
What is sterilization used for?
Surgical and lab equipment, surgical dressings, etc
Prions may be resistant
What are vegetative cells?
They actively grow and divide
What type of cell is an endospore?
Dormant cell
What are the 3 ways you can control microbial growth outside the body?
- Sanitation
- Antisepsis
- Degerming
What is sanitation?
Treatments aimed at lowering the # of microbes (in public places)
Ex: drinking water, utensils in restaurants
What is antisepsis?
The killing of vegetative microbial cells on the surface of the body
How is antisepsis accomplished?
By chemicals (antimicrobials)
What is degerming?
Removal of microbes from a limited area of the body
- Mechanical removal (scrubbing)
(Ex: wiping a needle with an alcohol swab before you inject someone)
What are the 3 ways to kill microbes?
- Alteration of Membrane Permeability
- Damage to Proteins
- Damage to Nucleic Acids
What is alteration of membrane permeability?
- Damage causes cellular contents to leak out
- The membrane is big target
What does dettol do to a cell?
It disrupts the cell wall and cell membrane
What is one of the oldest disinfectants?
Phenol (carbolic acid)
How can proteins be damaged?
- Heat
- pH
- Chemicals
What are enzymes important for?
All cellular functions
What happens if we damage proteins?
We can shut down the metabolism of the cell
Proteins do all the work in a cell, they are used as enzymes
Describe damage to nucleic acids
- DNA is damaged by heat/UV/radiation/chemicals
- mutations and replication errors occur
What is the easiest way to damage DNA?
UV radiation
What can damage to nucleic acids be used for?
- Food (doesn’t damage the food)
- Quite effective in killing microbes
What does the effectiveness of anti-microbial treatment depend on? (5)
- Object being treated
- # of microbes
- Environment (presence of blood, feces, vomit, temperature, biofilms, etc)
- Exposure time (increase exposure = increased killing) and (increased exposure at lower temp = increased killing)
- Microbial characteristics/susceptibilities (presence and type of cell wall) and (enveloped virus vs. naked virus)
What does lower temperature mean for microbes?
It is easier to kill them and slows their growth
Are gram (-) easier or harder to kill and why?
Harder d/t the two membranes
Is an enveloped virus easier or harder to destroy?
Easier to destroy
List the most resistant to the most susceptible of microbial susceptibilities to control agents? (10)
- Prions
- Endospores (of bacteria)
- Mycobacteria
- Cysts (of Protozoa)
- Vegetative Protozoa
- Gram-negative Bacteria
- Fungi (& Fungal Spores)
- Non-enveloped Viruses
- Gram-positive Bacteria
- Enveloped Viruses
Give 2 examples of Enveloped Viruses
HIV, Influenza
Enveloped viruses in the body vs a surface
Body: harder to kill
Surface: easier to kill if it is on an inanimate object because it is surrounded by a membrane
Growing state of gram (+)
Growing state pretty susceptible but can form endospores
How can you kill fungi?
Using bleach
What are vegetative protozoa doing?
Actively dividing
Are cysts hard to kill?
It is tougher to kill dormant cysts
How can you kill endospores
- Flaming an inoculating loop
- Use an autoclave when making media
What is the only way to ensure prions are killed?
Through burning
What do non-enveloped viruses have to do first?
Denature the protein coat first
What are the physical methods of microbial control?
- Heat
- Low temperatures
- Filtration
- Desiccation
- Radiation
- Osmotic Pressure
When deciding to kill something, what should you consider
How it will affect the infected material (biotic and abiotic)
What is pasteurization?
Using high heat for a short period of time
What does freezing kill?
Some microbes but not bacteria . Multicellular parasites (ex: sushi) will be killed by freezing the meat
What is filtration?
physically removing microbes by passing a filter through the microbes
What is desiccation?
Will not kill endospores but will cause the item to make endospores
Radiation and Microbial Control
UV and higher ionizing radiation is quite effective of killing bacteria
What are the 3 ways of providing heat to control microbes?
- Pasteurization
- Moist heat/High pressure
- Dry heat
What does heat do to proteins?
Denture them and increases membrane fluidity
What will pasteurization leave behind?
Endospores
What will endospores give rise to
Vegetative cells (expiry date)
What is pasteruization?
Heat food enough to kill the microbes, but not ruin the food
What may survive pasteurization?
Thermophilic organisms and endospores may survive
- May germinate after the “best before” date
What does Moist heat (boiling) kill?
Most bacteria, fungus, protozoa, and viruses
What does moist heat destroy?
May destroy endospores or thermophiles
What does moist heat do?
Denatures and causes the coagulation of proteins
What is autoclaving (moist heat)
Steam under pressure kills vegetative cells and endospores in 20 mins
What is autoclaving used for?
Solid objects and solutions
What is autoclaving used for?
To sterilize waste and the media. The pressure will damage cell walls and the high heat will denature proteins
(Will not kill prions but those are rare)
What is a physical method of microbial control (D.H)
Dry heat: using intense heat
How does dry heat kill microbes?
It kills by oxidation (burning) through flaming, incineration, and hot-air sterilization
How does freezing kill microbes? (physical method of microbial control)
The cells are ruptured by the ice crystals
Does freezing have an effect on endospores?
No
What effect does freezing have on vegetative cells
They will survive but become dormant
What does freezing drying prevent?
Microbial metabolism
What is freezing drying - low temperatures (physical methods of microbial control)?
AKA Lyophilization
- Rapid freezing followed by sublimation (skip the liquid phase)
What does the temperature 0-7 degrees celsius do?
Slows down metabolic pathways of microbes
Name an organism that is not affected by refrigeration
Psychrophiles which grow well in cold temperatures
Ex: some moulds, Listeria monocytogenes
Name a type of physical method to control microbes (F)
Filtration
What is desiccation (Physical method)
- Removal of water
- Microbes often remain viable
- Viruses and endospores are unaffected only inactive until the material becomes moist again
What is osmotic pressure (Physical method)
Adding solute (eg. sugar, salt) to a solution makes it hypertonic (increases the osmotic pressure)
What is osmosis?
Movement of water across a membrane
What is radiation?
High energy waves/particles damage DNA
What is UV radiation effective on?
Making breaks in DNA and really good at sterilizing food or plastic because it does not change the structure or chemistry of the object being radiated
What is radiation?
High energy waves/particles damage DNA
What is UV radiation effective on?
Making breaks in DNA and really good at sterilizing food or plastic because it does not change the structure or chemistry of the object being radiated
What are 3 types of radiation?
- X-rays
- Gamma rays
- Electron beams
What is irradiated food?
The bacteria population is reset, killing the existing bacteria. Food will stay fresher for longer
What is non-ionizing radiation?
- UV (longer wavelength than ionizing radiation)
- Germicidal lamps in nurseries to purify air
Can radiation kill spores?
Yes but they need longer exposure
Name 3 examples of chemical disinfectants
ABX, alcohols, heavy metals
What do chemical disinfectants destroy?
Can destroy proteins, cell walls, nucleic acids, etc.
Define volatile
Evaporates very rapidly
Describe Phenol and Phenolics (chemical disinfectant)
- denature protein and disrupt liquid
- stable and persistent
- smelly and can irritate skin
Describe alcohol (chemical disinfectant)
- denature proteins, dissolve lipids
- effective against fungi and bacteria
- very volatile
What are examples of halogens (chemical disinfectants)
Iodine, Bleach
What is halogen composed of?
Iodine, Chlorine
What is an example of peroxygens?
Ozone (O3), Hydrogen Peroxide (H2O2)
Describe Peroxygens (Chemical Disinfectant) - 4
- Oxidizing agents
- Generate O2 when they break down
- Effective against endospores
- Will denature proteins and enzymes
Describe surfactants (4)
- Mostly degerming
- Some have antimicrobial agents
- Breakup oils and membranes
- Hydrophilic/hydrophobic molecules that emulsify oily layers
Describe surfactants
- Mostly degerming
- Some have antimicrobial agents
- Breakup oils and membranes
- Hydrophilic/hydrophobic molecules that emulsify oily layers
Surfactants and biofilms
Detergents and soaps emulsify oils and help remove biofilms
Name 3 examples of heavy metals (C.D)
Silver (Ag), Mercury (Mg), Copper (Cu)
What do heavy metals do? (C.D)
Denature proteins by combining with Sulfur on amino acids
What is aldehyde used on (C.D)?
Hospital instruments and respiration equipment
Give an example of aldehyde?
Formaldehyde
What is a disadvantage of aldehyde?
Expensive, Carcinogen
Describe aldehyde and what they do
- Effective broad spectrum antimicrobials
- Inactivate proteins by cross-linking them
Describe gaseous compounds (3)
- Denatures proteins or cross links them
- Requires long exposure
- Easily penetrates porous material and is not persistent
Give an example of gaseous compounds and what is it used on? (C.D)
Ex: Ethylene oxide
Can be used on medical equipment that cannot be heated (ex: catheters)
What are abx used for (C.D)?
Molecular biology labs to make selective media and treatment rather than disinfecting
How can you evaluate a disinfectant?
The In Use Test
What is the “the in use test”?
Swab before and after disinfection and test for growth
What are the cons of “The In Use Test?”
Time consuming, Expensive, May lack consistency
What is the disk-dissusion test?
Filter papers soaked with disinfectant. The zone of inhibition around the disk is measured
What are the three different bacterial standards?
- Salmonella cholerasuis
- Staphylococcus aureus
- Pseudmonas aeruginosa
What is the dilution test?
- Metal rings dipped in test bacteria and dried
- Dried cultures are placed in disinfectant of varying concentrations for 10 mins at 20 degrees Celsius
- Rings are transferred to culture media to determine whether bacteria survived treatment
