[PL 3.3] STERILIZATION AND DISINFECTION: PHYSICAL METHODS

Which type of heat sterilization works by denaturation and coagulation of microbial proteins?

Moist Heat

Which type of heat sterilization works through oxidation?

Dry Heat

Which form of moist heat involves heating at 63°C for 30 mins or 72°C for 15 seconds?

Pasteurization

Which moist heat method involves boiling at 100°C to kill most pathogens (but not spores)?

Boiling

What moist heat method sterilizes via pressurized steam at 121°C for 15–30 minutes?

Autoclave

Which method involves 3 successive days of steaming to kill spores?

Tyndallization

What moist heat sterilization method is used for media with high protein content?

Inspissation

Which dry heat method uses an open flame to sterilize instruments like inoculating loops?

Flaming

Which dry heat method uses a hot air oven at 160–180°C for 1.5–2 hours?

Dry Oven

What method uses extreme dry heat to burn materials into ash?

Incineration

Which type of heat sterilization requires shorter contact time for effectiveness?

Moist Heat

Which type of heat sterilization requires longer exposure and higher temperature?

Dry Heat

What moist heat method kills pathogens in milk and prevents spoilage without affecting flavor?

Pasteurization

Which pasteurization method can sterilize milk?

Ultra-High Temperature (UHT) Pasteurization

Which two pasteurization methods kill vegetative pathogens but do NOT sterilize?

Batch and Flash Pasteurization

What moist heat method kills vegetative pathogens and most viruses in 15 minutes at 100°C?

Boiling

Which sterilization method is preferred for dishes, basins, and general equipment?

Boiling

Which method uses steam at 121°C and 15 psi for 15 minutes to sterilize materials?

Autoclave

What is the preferred sterilization method for heat-stable items and biohazardous waste?

Autoclave

What organism is used as a biological indicator for autoclave efficacy?

Geobacillus stearothermophilus

What type of autoclave is commonly used in labs and hospitals?

Vertical or Horizontal Autoclave

Name one autoclave type used in homes or small-scale settings

Pressure Cooker Type

What is the standard autoclave setting for biological waste in a gravity displacement sterilizer?

30 minutes at 121°C

What is the autoclave setting for biological waste in a prevacuum sterilizer?

4 minutes at 132°C

What is the sterilization time and temperature for infectious medical waste?

30–60 minutes at 132°C

Which sterilizer removes air by gravity or steam displacement?

Displacement Sterilizer

Which sterilizer uses vacuum to remove air before steam enters?

Prevacuum Sterilizer

How long and at what temperature should prions be autoclaved using a prevacuum sterilizer?

134°C for 18 minutes

What is the setting to kill prions in a gravity displacement sterilizer?

132°C for 1 hour

What chemical is used for prion decontamination before autoclaving?

1 N sodium hydroxide

What is the prion sterilization procedure using NaOH and gravity autoclaving?

1 hr NaOH + autoclave at 121°C for 1 hr

How long should you heat prions at 121°C after NaOH immersion?

30 minutes

What is the method of sterilization that involves exposure to steam for 20 minutes over three days?

Tyndallization

What equipment is used in Tyndallization?

Koch’s or Arnold’s Sterilizer

Which sterilization technique involves thickening through evaporation?

Inspissation

What device is used to perform inspissation?

Inspissator

At what temperature and duration is inspissation carried out?

70–80°C for 2 hours for 3 days

For what type of culture media is inspissation used?

Heat-sensitive media (with egg or serum)

What dry heat method uses an open flame to destroy microorganisms?

Flaming

What is the preferred use of the flaming method?

Metal loops and needles

Which dry heat method uses high temperatures (160–180°C) for 1.5–3 hours?

Hot-Air Oven

What is the hot-air oven used to sterilize?

Glassware, oils, powders

What sterilization method burns material at 870–980°C into ashes?

Incineration

What type of waste is disposed of using incineration?

Paper cups, dressings, carcasses, wipes

Which pasteurization method uses 63°C for 30 minutes?

Batch Method

What is the time and temperature used in the Batch Method?

63°C for 30 minutes

What is the application of the Batch Method?

Disinfects and kills pathogens

Which pasteurization method uses 72°C for 15 seconds?

Flash Method

What is the time and temperature used in the Flash Method?

72°C for 15 seconds

What is the application of the Flash Method?

Disinfects and kills pathogens (high-temp short-time)

Which pasteurization method uses 140°C for 3 seconds?

Ultra-High Temperature (UHT)

What is the time and temperature used in UHT?

140°C for 3 seconds

What is the application of UHT?

Sterilizes; rapid cooling in a vacuum chamber

What method separates microorganisms from liquids or gases?

Filtration

Which microbial control method is used for heat-sensitive materials?

Filtration

What type of filtration uses cellulose acetate or nitrate membranes under vacuum?

Liquid Filtration

What is the critical pore size used for sterilization in liquid filtration?

0.22 µm

What is the standard pore size for general microbial removal?

0.45 to 0.80 µm

What type of filtration uses HEPA filters to remove particles larger than 0.3 µm?

Air Filtration

Where is air filtration with HEPA filters typically used?

Isolation rooms, operating rooms, biosafety cabinets

What is the mechanism of osmotic pressure in microbial control?

Plasmolysis

Which method is used for food preservation through high solute concentration?

Osmotic Pressure

Which method disrupts microbial metabolism through drying?

Desiccation

Which food preservation method is primarily bacteriostatic and involves drying?

Desiccation

What preservation method involves removing water to stop metabolism?

Desiccation

What is the mechanism of cold in microbial control?

Decreased chemical reactions and possible protein changes

Which method is used to preserve food, drugs, and microbial cultures?

Cold

What is the effect and temperature of refrigeration on microbial growth?

Slows metabolism; ~4°C

Which method freezes microbes at temperatures between -50°C to -95°C?

Deep-freezing

What is the name of the freeze-drying process for preserving microbes?

Lyophilization

How does lyophilization preserve microbial cultures?

Water is removed by high vacuum at low temperature

Which is the most effective long-term microbial preservation method?

Lyophilization

What type of radiation uses gamma rays to sterilize disposables like syringes and catheters?

Ionizing Radiation

What biological indicator is used to monitor ionizing radiation sterilization?

Bacillus pumilus

What is the mechanism of action of ionizing radiation on microbes?

Destruction of DNA

What is the preferred use of ionizing radiation in medical settings?

Sterilizing pharmaceuticals and medical/dental supplies

What type of radiation uses ultraviolet light for microbial control?

Non-Ionizing Radiation

Why does non-ionizing radiation require direct surface exposure?

Poor penetration

What is the mechanism of action of non-ionizing radiation on DNA?

Damage to DNA

Where is non-ionizing radiation most commonly used for disinfection?

Closed environments with UV (germicidal) lamps