Chapter 7 Flashcards
What does sepsis refer to in microbiology?
In microbiology, sepsis refers to bacterial contamination. (Example: Septic Tank)
What does asepsis refer to in microbiology?
Asepsis in microbiology refers to the absence of significant microbial contamination.
What is the purpose of aseptic surgery techniques?
Aseptic surgery techniques are used to prevent microbial contamination of wounds and surgical sites.
Name three practices for controlling microbial growth.
- sterilization
- disinfection
- biocide/germacide
What is the difference between disinfection and sterilization?
Disinfection involves reducing microbial activity to a level that is considered safe for public health. Sterilization, on the other hand, completely eliminates all forms of microbial life.
What is sterilization in microbiology?
Sterilization refers to the complete removal and destruction of all microbial life.
What is disinfection in microbiology?
Disinfection involves the process of destroying harmful microorganisms, typically on inanimate objects or surfaces.
What is the purpose of commercial sterilization in the food industry?
Commercial sterilization is used to kill Clostridium botulinum endospores in canned goods to prevent foodborne illnesses.
What is antisepsis, and where is it commonly used?
Antisepsis is the destruction of harmful microorganisms from living tissue. It is often used with antiseptics to disinfect wounds and living tissues.
Explain the concepts of degerming and sanitization in microbiology.
- Degerming is the mechanical removal of microbes from a limited area, typically through cleaning.
- Sanitization involves reducing microbial counts on eating utensils to safe levels, ensuring they are safe for use.
What are biocides (germicides) in microbiology?
Biocides, also known as germicides, are treatments that are designed to kill microbes.
What is the purpose of a fungicide in microbiology?
A fungicide is used to kill fungi, preventing their growth and reproduction.
Define a virucide in microbiology.
A virucide is a substance or treatment that inactivates or destroys viruses.
What is bacteriostasis, and how does it work?
Bacteriostasis refers to the inhibition of the growth and multiplication of microbes. When a bacteriostatic agent is removed, microbial growth may resume.
One common application of bacteriostasis is in the manufacture of plastics.
How do agents affect microbial membranes?
Agents can alter membrane permeability, leading to membrane leaks (lysis) and microbial death.
What happens when microbial proteins are damaged?
Damaged proteins, often referred to as “little bags of enzymes,” denature due to factors like heat and chemicals, disrupting essential microbial processes.
How do agents cause damage to microbial nucleic acids, and what are the consequences?
- Agents can damage nucleic acids through heat, chemicals, and UV radiation.
- Rendering microbes incapable of replication and protein synthesis, thereby inhibiting their growth and reproduction.
Factors that affect microbial death rates
What is one factor that affects the death rate of microbes?
The number of microbes present. More microbes generally result in a longer time required for their death.
Factors that affect microbial death rates
What are some environmental influences that can affect microbial death rates?
Environmental factors include:
1. The presence of organic matter
2. The presence of biofilms
3. The nature of the suspending medium (such as heat treatment), and temperature.
Factors that affect microbial death rates
What are the four factors affecting microbial death rates?
- Number of microbes (More microbes, longer it takes)
- Environmental influences (Presence of organic matter, biofilms)
- Time of exposure
- Characteristics of microbe (antibiotic resistance)
How does the time of exposure impact the effectiveness of chemical antimicrobials?
Chemical antimicrobials often require extended exposure time to effectively kill microbes.
What is another factor that influences the death rate of microbes?
Think of special characteristics of bacteria: Does it have resistance against antibiotics? Does it produce toxins?
The characteristics of the microbe itself can also impact its susceptibility to antimicrobial treatments
What are some environmental factors that affect the growth of microorganisms?
Environmental factors include:
1. Heat (both dry and moist heat)
2. boiling
3. autoclaving
4. pasteurization, filtration
5. low temperature
6. radiation (both nonionizing and ionizing)
7. osmotic pressure
Moist heat is used to kill microorganisms. What are examples of moist heat and the procedures used to kill them?
- Boiling
- Autoclaving
- Pasteurization
What is the thermal death point (TDP), and what does it indicate?
The thermal death point (TDP) is the lowest temperature at which all microbes in a particular liquid suspension will be killed in 10 minutes. It indicates the minimum temperature required for complete microbial destruction.
What is the thermal death time (TDT), and what does it represent?
The thermal death time (TDT) is the minimal length of time required for all microbes in a liquid culture to be killed at a given temperature. It indicates the time needed for microbial sterilization at that specific temperature.
How is the decimal reduction time (DRT) defined?
The decimal reduction time (DRT) is the time, in minutes, in which 90% of a population of bacteria at a given temperature will be killed. It measures the effectiveness of heat treatment in reducing microbial numbers.
How does dry heat primarily kill microbes, and what are some methods of dry heat sterilization?
Dry heat kills microbes through oxidation effects. Methods of dry heat sterilization include direct flaming, hot air sterilization (items placed in an oven), and maintaining 170°C for 2 hours to ensure sterilization.
How does moist heat sterilization work, and what are some common methods?
Moist heat coagulates proteins. Methods include free-flowing steam, autoclave (121°C, 15 psi, 15 min), boiling, and pasteurization.
What are the key characteristics of autoclave sterilization?
Autoclave sterilization uses steam under pressure at 121°C, 15 psi, for 15 minutes. Effective when steam contacts the item directly or in a small aqueous solution.
What is pasteurization, and what products are commonly pasteurized?
Pasteurization mildly heats products to kill microbes while preserving taste. Phosphatase test verifies pasteurization.
Used for milk, beer, yogurt. They each take a different amount of time to be pasteruized.
What is filtration in microbiology, and what can it remove?
Filtration passes substances through a screen-like material. It removes microbes of various sizes, with some filters as small as 0.01 μm capable of filtering out viruses and large proteins.
CAN NOT remove flexible bacteria (spirochetes) & wall-less mycoplasma
What are some low-temperature microbial control methods, and how do they work?
Low-temperature methods include:
* Refrigeration (0-7°C) these put the bacteria in a bacteriostatic effect
* Fast freezing in deep freezers
* Slow freezing in regular freezers. Slow freezing can harm microbes by disrupting their cellular and molecular structure.
Radiation used to kill microbes
How does ionizing radiation work for microbial control, and what types are commonly used?
Ionizing radiation (e.g., X-rays, gamma rays, electron beams) ionizes water to create reactive hydroxyl radicals, damaging microbial DNA through lethal mutations.
What is nonionizing radiation, and how does it affect microbial control?
Nonionizing radiation (e.g., ultraviolet) damages microbial DNA by creating thymine dimers, making it effective for microbial control.
How do microwaves impact microbial control?
Microwaves primarily kill microbes through heat rather than direct antimicrobial action.
Not as effective as ionizing and nonionzing radiation.
Which physical methods of controlling microbes are bacteriostatic?
- Low temp: Refrigeration (0-7 celsius)
- Heavy metals: Mercury
- Aldehydes: Glutaraldehyde when used in a 2% solution
How does osmotic pressure control growth of microbes?
- Hypertonic solution: Cell goes through plasmolysis (water leaves cell)
- Hypotonic solution: Cell gets lyzed (water rushes into cell and it bursts)
There are 8 chemical methods of microbial control, each of them as a mode of action. What are they?
- Alcohols: Usually denatures protein. Can also disrupt membranes and dissolve many lipids
- Phenols & Phenolics: Injure lipids of plasma membranes causing leakage
- Heavy metals: Denature proteins
-
Biguandies: Disrupt plamsa membranes (especially gram-positive bacteria)
5A. Halogens-Iodine: Impairs protein synthesis and alters cell membranes
5B. Halogens-Chlorine: Prevents cellular enzyme system from functioning - Surfractants: Decrease surface tension among molecules of a liquid
- Oxidizing Agents: Oxidization
- Aldehydes: Inactivates proteins by forming covalent cross links with organic groups
Iodine is the oldest and most effective antiseptic.
What are examples of alcohols that destroy microbes?
- Ethanol
- Isopropanol
AKA Purell and GermX
Phenols and Phenolics are in the brand Lysol. What is the main ingredient in Lysol?
Cresols: Triclosan (Bisphenol)
Surfractants are in soap and detergents. How are surfractants used to destroy microbes on the human body?
- When we use soap we must mechanically remove microbes through scrubbing.
- Emulsification is also used (breaking oily film into tiny drops)
What is the only example of Biguanides that was shared in class?
Mouthwash
What are examples of Halogens?
- Iodine (Ex. Potatble Aqua pills)
- Chlorine
Chlorine aka Sodium hypochlorite (Ex. Clorox)
What are examples of heavy metals that can destroy microbes?
- Silver
- Copper
- Zinc
There are two chemicals that act as sterilants, what are they?
- Oxidizing agent: Peracetic Acid
- Aldehyde: Glutaraledehyde
Mircobial death curve
What is the most resistant microbe? What is the least resistant microbe?
Most resistant = Prions and Endospores
Least resistant = Gram-positive bacteria and Virsues with lipid envelopes
