Controlling Microbial Growth Flashcards
What is sterilization?
Destruction or removal of all viable organisms.
What is disinfection?
Killing, inhibiting, or removing disease causing (pathogenic) organisms.
What is sanitization?
Reduction of microbial population to levels deemed safe.
What are disinfectants?
Agents, usually chemical, used for disinfection, usually used on inanimate objects.
What is antisepsis?
Prevention of infection of living tissue by microorganisms.
What are antiseptics?
Agents that kill or inhibit the growth of microorganisms when applied to tissue.
What is chemotherapy?
Using chemicals to kill or inhibit the growth of microorganisms within host tissue.
What are -cidal agents?
Agents that are used to kill specific types of organisms.
What are -static agents?
Agents that inhibit the growth of specific types of organisms.
What is the pattern of microbial death?
Population declines exponentially.
How is an agent’s killing efficiency measured?
By measuring the decimal reduction time.
What is decimal reduction time?
The time it takes for the agent to kill 90% of the microbes.
*Must be sure VBNC cells are dead.
What are the 4 methods of microbial control?
- Physical agents.
- Chemical agents.
- Mechanical removal methods.
- Biological agents.
What does filtration allow for?
The reduction of the microbial population by removing microorganisms.
How does liquid filtration work?
A porous membrane with defined pore sizes removes microorganisms by physical screening.
How does air filtration work?
Similar to how liquid filtration works. In a BSC, laminar air flow and HEPA filters are used.
What are the methods of moist heat control?
- Pasteurization.
- Boiling.
- Steam sterilization.
What is moist heat able to destroy?
- Viruses.
- Fungi.
- Bacteria.
What can boiling not destroy?
Endospores.
*Cannot sterilize.
How does moist heat destroy microbes?
- Degrade nucleic acids.
- Denature proteins.
- Disrupt membranes.
At what temperature is steam sterilization carried out?
Above 100 C, which requires saturated steam under pressure.
What device uses steam sterilization?
An autoclave.
What microbes is steam sterilization effective against?
All of them.
What is pasteurization?
Controlled heating at temperature well below boiling.
What does pasteurization do?
Reduces the total number of pathogens present, slowing spoilage.
What products is pasteurization used on?
- Milk.
- Beer.
- Cheese.
- Yogurt.
What is dry heat sterilization?
Subjecting an item to temperatures of 160-170 C for 2-3 hours.
How does dry heat sterilization impact microbes?
- Oxidizes cell constituents.
- Denatures proteins.
Why would dry heat be used over moist heat?
- To avoid corroding glassware and metal instruments.
- Less expensive.
What wavelength is most bactericidal?
260 nm (ultraviolet).
What does UV radiation cause?
Thymine dimerization, preventing replication and transcription.
Why is UV light limited to surface sterilization?
It cannot penetrate many substances.
*Has been used to treat water.
Why is ionizing radiation used?
It can penetrate deep into objects and destroy endospores.
*No always effective against viruses.
What processes is ionizing radiation used in?
- Sterilization.
- Pasteurization of hormones, antibiotics, sutures, plastic disposable supplies, and food.
What are biological agents for microbial control?
- Bacteriophages.
- Pathogen-specific bacteriophage lysins.
- Bacteriocins
What are bacteriocins?
Bacterial proteins that inhibit the growth of similar strains of bacteria.
What falls under chemical agents?
- Phenolics.
- Heavy metals.
- Halogens.
- Aldehydes.
- Alcohols.
- Sterilizing gases.
- Quaternary Ammonium Compounds.
Where are phenolics commonly used?
Laboratories and hospitals as disinfectants.
How do phenolics impact microbes?
- Denaturing proteins.
- Disrupting cell membranes.
*Tuberculocidal.
What are the downsides of phenolics?
- Disagreeable odor.
- Can cause skin irritation.
Which chemical agent is the most widely used disinfectant, antiseptic, and sanitizer?
Alcohols.
What are the two most common types of alcohols used?
- Ethanol.
- Isopropanol.
What microbes do alcohols kill?
- Bacteria.
- Fungi.
*Not spores and inactivates some viruses.
How do alcohols impact microbes?
- Possibly dissolve membrane lipids.
- Denature proteins.
What is the main function of Iodine halogens?
Skin antiseptics.
How do iodine halogens impact cells?
- Oxidizes cell constituents.
- Iodinates proteins.
*May kill endospores at high concentrations.
What are the downsides of using halogens?
- Skin damage.
- Skin staining.
- Allergies.
What is the main function of chlorine halogens?
- To disinfect water supplies and swimming pools.
- As a disinfectant in the dairy and food industries.
- As a household disinfectant.
How do chlorine halogens impact microbes?
Oxidizes cell constituents.
*Destroys vegetative bacteria, fungi, and kills spores.
What specific metals are used to control microbes?
- Mercury.
- Arsenic.
- Zinc.
- Copper.
- Silver.
What is the downside of using heavy metals?
They are toxic to the body/have off-target effects.
What effect do heavy metals have on microbes?
Inactivates proteins and may precipitate cell proteins.
What common agents are aldehydes?
- Glutaraldehyde.
- Formaldehyde.
What are the characteristic of aldehydes as chemical agents?
- Highly reactive.
- Sporicidal.
- Can be used as a sterilant.
What are sterilizing gases used for?
To sterilize heat sensitive material.
What are the characteristics of sterilizing gases?
- Sporicidal.
- Microbial.
What two gases are commonly used as sterilizing gases?
- Ethylene oxide.
- Hydrogen peroxide.
What agency regulates disinfectants? Agents used on humans and animals?
- EPA.
- FDA.
What are 6 conditions that influence the effectiveness of antimicrobial agent activity?
- Population size.
- Population composition.
- Concentration/intensity of an antimicrobial agent.
- Contact time.
- Temperature.
- Local environment.
How does population size impact effectiveness?
Larger populations take longer to kill than smaller populations.
How does population composition impact effectiveness?
Microorganisms have different sensitivity to antimicrobial agents.
How does concentration/intensity of the antimicrobial agent impact effectiveness?
Higher concentrations kill more rapidly, but the relationship is not linear.
How does contact time impact effectiveness?
Longer exposure, more organisms killed.
How does temperature impact effectiveness?
Higher temperature enhances chemical activity.
How does local environment impact effectiveness?
The pH, concentration, and viscosity of organic matter determine how well antimicrobial agents can interact with the microbes.
*Organisms in biofilms are less susceptible to many antimicrobial agents.
