22 Questions
Which of the following is NOT a physical method for microbial control?
Phenolics
Which of the following chemical agents is most effective against bacterial spores?
Aldehydes
What is the primary mechanism by which sonication destroys microbial cells?
Disruption of cell structures due to rapid changes in pressure
Which of the following physical methods for microbial control relies on the reduction of water content?
Lyophilization
Which type of chemical agent is commonly used as a disinfectant in hospitals and healthcare settings?
Phenolics
What is the primary advantage of using HEPA filtration for microbial control?
Ability to remove even the smallest microbial cells and particles
Which of the following is NOT a physical method for microbial control?
Phenolics
Which type of radiation is ionizing and can be used for microbial control?
X-rays
Which of the following is NOT a type of moist heat used for microbial control?
Incineration
Which of the following chemical agents is a halogen used for microbial control?
Chlorine
Which of the following is a surface-acting agent used for microbial control?
Quaternary ammonium compounds
Which of the following is a method of microbial control that involves removing water from microorganisms?
Lyophilization
Which of the following is the primary mechanism of action for alcohol-based antimicrobial agents?
Denaturation of proteins and dissolution of lipids
Which of the following types of filtration is used to remove microbes from air, including some viruses?
HEPA filtration
Which of the following chemical agents is known for its ability to inactivate proteins by crosslinking to numerous functional groups, including amino, hydroxyl, carboxyl, and sulfhydryl groups?
Aldehydes
Which of the following methods of microbial control involves the use of high-frequency sound waves to disrupt microbial cells?
Sonication
Which of the following criteria is NOT considered when selecting a suitable chemical agent for microbial control?
High cost and limited availability
Which of the following physical methods of microbial control involves the removal of water from microorganisms, leading to their inactivation?
Desiccation
Which of the following chemical agents is known for its ability to oxidize cell constituents, especially proteins at sulfhydryl groups, and iodinates proteins, frequently at tyrosine residues?
Halogens
Which of the following methods of microbial control involves the use of high temperatures to inactivate microorganisms?
Both moist heat and dry heat
Which of the following chemical agents are known for their ability to disrupt microbial membranes and potentially inactivate some proteins?
Quaternary ammonium compounds
Which of the following methods of microbial control involves the use of ionizing or non-ionizing radiation to inactivate microorganisms?
Radiation
Study Notes
Control of Microorganisms
- Control of microorganisms involves sterilization, disinfection, sanitization, and antisepsis
- Conditions influencing effectiveness of antimicrobial agents include type of microorganism, concentration and type of antimicrobial agent, exposure time, temperature, and pH
Physical Methods for Microbial Control
- Heat: moist heat (boiling, autoclave, pasteurization), dry heat (hot air oven, incineration)
- Cold: refrigeration, freezing
- Desiccation: simple desiccation, reduce water content, lyophilization
- Radiation: ionizing (e.g. X-ray), non-ionizing (e.g. ultraviolet light)
- Sonication: use of high-frequency ultrasound waves
- Filtration: membrane filtration, HEPA filtration
Microbial Control using Heat
- Moist heat: boiling, autoclave, pasteurization
- Dry heat: hot air oven, incineration
Microbial Control using Cold
- Refrigeration, freezing
Microbial Control using Desiccation
- Simple desiccation, reduce water content, lyophilization
Microbial Control using Radiation
- Ionizing: X-ray
- Non-ionizing: ultraviolet light (260 nm), germicidal lamps in hospitals
Microbial Control using Sonication
- Use of high-frequency ultrasound waves (up to 20KHz)
- Causes rapid changes in pressure within the intracellular liquid leading to cavitation (formation of bubbles inside the cell)
- Disrupts cell structures (cell-lysis)
Microbial Control using Filtration
- Membrane Filtration: use of membrane filter with 0.2 µm or smaller pore size
- HEPA Filtration: use of High-efficiency particulate air (HEPA) filter with 0.3-µm pore size
Chemical Methods for Microbial Control
- Selection of chemical agent: rapid action, solubility and long-term stability, broad spectrum action, non-toxic to human and animal tissues, penetration of inanimate surfaces, resistance to becoming inactivated by organic matter, non-corrosive/non-staining, sanitizing/deodorizing, affordable and readily available
Types of Chemical Agents
- Phenolics: first widely used antiseptic and disinfectant, mechanism of action: denatures protein; disrupts membranes
- Alcohols: most widely used disinfectants and antiseptics, mechanism of action: denatures proteins; dissolves lipids
- Halogens: iodine and chlorine are important antimicrobial agents, mechanism of action: oxidizes cell constituents, especially proteins at –SH groups; iodinates proteins and inactivates them frequently at tyrosine residues
- Surface Acting Agents: quaternary ammonium compounds, mechanism of action: disrupts membranes, may inactivate some proteins
- Aldehydes: formaldehyde and glutaraldehyde, mechanism of action: inactivates proteins by crosslinking to numerous functional groups on proteins including (-NH2, -OH, -COOH, -SH)
- Sterilizing Gases: ethylene oxide gas (EtO), mechanism of action: inactivates proteins by alkylating them
Test your knowledge on microbial filtration methods like membrane filtration and HEPA filtration. Learn how these methods are used to physically remove microbes from liquid solutions and air, respectively.
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