Microbial Control Methods - VOCABULARY Flashcards

70 vocabulary-style flashcards covering physical, chemical, and biological microbial control methods described in the notes.

Dry heat

Sterilization by dry heat (oxidation); less effective than moist heat.

Moist heat

Kills by coagulating proteins; more effective than dry heat; includes boiling, autoclave, and pasteurization.

Autoclave

Chamber using steam under pressure; typically 121°C at 2 atm; kills all organisms and endospores.

Direct Flaming

Sterilize loops/needles by heating to red-hot in an open flame.

Incineration

Destruction of waste and disposables by burning.

Hot air sterilization

Dry heat sterilization in an oven; slower than moist heat; about 2 hours at 170°C.

Thermal Death Point (TDP)

Lowest temperature at which all microbes in a liquid are killed in 10 minutes.

Thermal Death Time (TDT)

Minimal time to kill all bacteria at a given temperature.

Decimal Reduction Time (D value)

Time required to kill 90% of microorganisms or spores at a given temperature.

Endospores

Heat-resistant, dormant bacterial forms requiring harsher conditions to kill.

Pasteurization

Controlled heat treatment to reduce microbes; does not guarantee complete sterility; preserves product.

Batch pasteurization

Historical method: 63–65°C for 30 minutes.

HTST (High Temperature Short Time)

Pasteurization at 72°C for 15 seconds.

UHT (Ultra High Temperature)

Pasteurization at 134°C for 1 second; shelf-stable product.

Ultrahigh-Temperature sterilization

Heat treatment at 140°C for 1–3 seconds; sterilizes.

Tyndallization

Intermittent steam sterilization with three exposures separated by ~23–24 hour incubations to germinate spores.

Filtration

Removal of microbes by passage through a membrane; used for heat-sensitive liquids.

HEPA filter

High-efficiency particulate air filter; removes 99.97% of particles ≥0.3 µm; used in ORs and safety cabinets.

Membrane filter

Filters with uniform pore size; used for sterilizing heat-sensitive liquids; various pore sizes.

0.22 µm pore filter

Removes most bacteria; does not retain spirochetes, mycoplasmas, or viruses.

0.45 µm pore filter

Removes largest bacteria; does not retain viruses.

0.01 µm pore filter

Retains all viruses and some large proteins.

Laminar flow biological safety cabinet

Work cabinet using HEPA-filtered air with a vertical sterile air curtain.

Laminar flow hood

Work space with laminar air flow used in cell culture to maintain sterility.

Desiccation

Drying; microbes cannot grow without water; viability may persist for years.

Osmotic pressure

High salt/sugar in foods creates hypertonic environment; bacteriostatic effect.

Plasmolysis

Water leaves cell; membrane shrinks away from cell wall.

Refrigeration

0–7°C; slows metabolism; bacteriostatic.

0–7°C

Temperature range used for refrigeration to slow microbial growth.

Freezing

Below 0°C; slows or halts growth; many microbes survive; some parasites killed over time.

Flash freezing

Very rapid freezing; often does not kill most microbes.

Slow freezing

Slower freezing forms ice crystals that damage cells; more microbial kill than flash freezing.

Bacteriostatic

Inhibits microbial growth rather than killing.

Radiation

Use of energy forms (ionizing, non-ionizing, and microwave) to kill microbes.

Ionizing radiation

Gamma rays, X-rays, electron beams; high energy; penetrates and sterilizes.

Non-ionizing radiation

UV light; damages DNA with thymine dimers; limited penetration.

Microwave radiation

Wavelength 1 mm to 1 m; heats via interaction with water molecules to kill microbes.

Gamma rays

Ionizing radiation used to sterilize medical supplies and foods; penetrative.

X-rays

Ionizing radiation used for sterilization of heat-sensitive items.

Electron beams

Ionizing radiation using high-energy electrons for rapid sterilization.

UV light

Non-ionizing radiation that damages DNA; poor penetration.

Germicidal lamps

UV lamps designed to disinfect surfaces and air.

Three steam exposures (Tyndallization)

Steam exposures repeated three times with incubation gaps to destroy spores.

Bdellovibrio spp. (B. bacteriovorus)

Gram-negative predators that reduce human intestinal pathogens.

Bacteriophage therapy

Therapy using bacteriophages to kill specific bacteria.

Lysins

Phage-derived enzymes that lyse bacterial cell walls.

Bacteriocins

Antibacterial toxins produced by bacteria to inhibit others.

Filter sterilization

Sterilizing heat-sensitive liquids by filtration through a membrane.

Pasteurization of milk

Milk heat-treated to reduce microbes and spoilage organisms; extends shelf life.

Pasteurization purpose

Reduce spoilage organisms and pathogens; not a guarantee of sterility.

121°C autoclave (2 atm)

Standard autoclave condition for steam sterilization.

Autoclave kill time (15 minutes)

All organisms and endospores are killed within about 15 minutes at standard autoclave conditions.

63°C for 30 minutes (historical pasteurization)

Historical batch pasteurization protocol.

72°C for 15 seconds (HTST)

High-temperature short-time pasteurization protocol.

134°C for 1 second (UHT)

Ultra-high temperature pasteurization protocol.

140°C for 1–3 seconds (ultrahigh-temperature sterilization)

Highest short heat treatment used for sterilization of milk.

Milk pasteurization reduces spoilage microbes

Pasteurization diminishes spoilage organisms and pathogens; not complete sterilization.

Autoclave direct steam contact

Most effective when organisms contact steam directly or are in a small liquid volume.

Endospores killed in autoclave (15 min)

Endospores are killed within about 15 minutes at 121°C/2 atm.

Phage lysins attack bacterial cell walls

Lysins lyse bacteria by hydrolyzing their cell walls.

Bacteriophage d'Herelle discovery

Felix d’Herelle isolated phages and showed their role in destroying dysentery bacteria.

Lysins as bacterial control

Phage-derived enzymes evaluated for controlling bacteria.

Filtration for vaccines, enzymes, antibiotics

Membrane filtration used to sterilize heat-sensitive products.

HEPA filter 0.3 µm capture

Removes 99.97% of particles ≥0.3 µm; used in safety cabinets and clean rooms.

UV does not penetrate glass

UV radiation is blocked by glass and other opaque surfaces; limited penetration.

UV damages skin and eyes

Non-ionizing UV radiation can harm skin and eyes.

Ionizing OH− radicals

Ionizing radiation generates hydroxyl radicals that damage DNA.

Microwave applications in food and healthcare

Used to cook/reheat foods, sterilize some heat-sensitive equipment, and treat some waste.