Controlling Microorganism Flashcards
What are the methods for controlling microorganisms?
Physical
Chemical
Mechanical
What is sterilization?
A process that destroys all viable microbes, including viruses and endospores.
What is disinfection?
A process to destroy vegetative pathogens, not endospores; used on inanimate objects.
What is disinfection?
A process to destroy vegetative pathogens, not endospores; used on inanimate objects.
What is an antiseptic?
Disinfectants applied directly to exposed body surfaces.
What is sanitization?
Any cleansing technique that mechanically removes microbes.
Modes of Action Cellular targets of physical and chemical agents: Cell wall
Becomes fragile, causing lysis
(e.g., antimicrobial drugs, detergents, alcohol).
Modes of Action Cellular targets of physical and chemical agents: Cell Membrane
The cell membrane: Loses integrity (e.g., detergent surfactants)
Modes of Action Cellular targets of physical and chemical agents: Protein and nucleic acid synthesis
Prevents replication, transcription, translation, and protein synthesis (e.g., chloramphenicol, UV radiation, formaldehyde).
Modes of Action Cellular targets of physical and chemical agents: Proteins
Disrupts or denatures proteins (e.g., alcohols, phenols, acids, heat)
How is microbial death defined?
Permanent loss of reproductive capability, even under optimum growth conditions.
What are the methods of physical microbial control?
-Heat (moist and dry)
-Cold temperatures
-Desiccation
-Radiation
-Filtration
What is the mode of action for moist heat?
More effective at lower temperatures and shorter exposure time due to the presence if water; coagulates and denatures proteins.
What is the mode of action for dry heat?
Moderate to high temperatures; dehydration, alters protein structure, incineration.
What is Thermal Death Time (TDT)?
The shortest time needed to kill all test microbes at a specific temperature.
What is steam under pressure used for?
Sterilization
(e.g., autoclave at 15 psi/121°C/10-40 min)
Tyndallization
intermittent sterilization for substances that cannot withstand autoclaving
- exposed to free-flowing steam for 30–60 minutes a day for 2-3 days
What does boiling water achieve?
Boiling at 100°C for 30 minutes destroys non-spore-forming pathogens (disinfection).
What is pasteurization?
-Heat treatment to kill pathogens without destroying flavor/value. (Not sterilization)
-Batch Method: 63–66°C for 30 min
-Flash Method: 71.6°C for 15 sec
What does dry heat do?
-Reduces microbes to ash.
-Dry ovens: 150–180°C, coagulates proteins.
What does cold temperature do to microbes?
Microbiostatic: slows growth (e.g., refrigeration 0–15°C and freezing).
What is desiccation?
Gradual removal of water, leading to metabolic inhibition; not very effective.
What is lyophilization?
Freeze-drying for microbial preservation.
What is ionizing radiation?
High penetrating power breaks DNA (gamma rays, X-rays, cathode rays)
-Used for sterilizing medical supplies and food.
