What temperature and pressure are required for effective sterilization in an autoclave?
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121ºC at 15 pounds per square inch (psi) for 15 minutes.
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What temperature and pressure are required for effective sterilization in an autoclave?
121ºC at 15 pounds per square inch (psi) for 15 minutes.
What is a key reminder about sterile working environments?
A completely sterile working environment does not exist.
What is the recommended filter size to ensure sterilization of fluids?
0.22-μm filter.
Why is a Bunsen burner not practical in a laminar flow unit?
Because the heat will disrupt airflow.
What is the minimum volume requirement for the vessel used to sterilize liquids?
At least twice the volume of the liquid to be autoclaved.
What materials should not be autoclaved?
Polyethylene and high-density polyethylene.
What is a significant hazard associated with a microincinerator?
The barrel gets extremely hot to the touch, posing a serious burns hazard.
What is a universally accepted norm in biological laboratories?
High standards of cleanliness.
What must microbiologists ensure about their materials before starting aseptic work?
That their materials are sterile.
What happens if cultures or media are uncapped for too long?
They become exposed to the air, increasing the risk of contamination.
What is the most common method of sterilization used by microbiologists?
Autoclaving.
What types of materials can be sterilized using dry heat?
Glassware, metal, and other heat-stable objects.
What is an alternative to a Bunsen burner for sterilizing inoculating loops?
A microincinerator.
What percentage of airborne particles must a certified HEPA filter capture?
A minimum of 99.97%.
What should researchers do before handling biological cultures?
Wash their hands often.
How should containers be capped or stoppered during autoclaving?
Loosely capped or stoppered to avoid shattering.
What indicates that sterilization conditions have been met?
A special indicator tape that changes color.
How does a microincinerator sterilize an inoculating loop?
By placing the loop or needle within a circular heating element that quickly heats and sterilizes it.
What is the purpose of the 'gravity' or 'fast exhaust' cycle?
For all dry items like glassware, maintaining pressure and temperature for a set time.
What pore size filter is commonly used to retain most living organisms?
0.45-μm filter.
What temperature range is used for oven sterilization?
Between 121°C and 170°C.
What is the purpose of the 'liquid' or 'slow exhaust' cycle?
To prevent explosive boil-overs in liquids by slowly releasing pressure.
Why must the autoclave not be overcrowded?
To allow steam to penetrate everywhere.
What type of glass is preferred for autoclaving liquids?
Heat resistant borosilicate glass (Pyrex).
What should be done with spills in the microbiology lab?
They must be cleaned and decontaminated immediately.
What is the primary use of a Bunsen burner in the lab?
To heat things quickly, sterilize inoculating loops, warm glass bottle necks, or ignite alcohol on culture spreaders.
What is the most important component of a laminar flow hood?
A high-efficiency bacteria-retentive filter (HEPA filter).
How does a Bunsen burner help maintain sterility?
By creating convection currents that lift particulates away from the experimental area.
How should dry items be prepared before autoclaving?
Wrapped in aluminum foil to prevent recontamination.
What should be avoided to maintain aseptic conditions?
Breathing on cultures or sterile instruments.
How often should autoclaves be tested?
Periodically, using biological tests such as bacterial spore test kits.
Where are filtering procedures usually carried out to avoid recontamination?
In a laminar flow unit or on a bench equipped with a Bunsen burner.
What type of tray should materials be placed in for autoclaving?
An autoclavable tray made of polypropylene plastic or stainless steel with sides at least 10 cm high.
What is the routine temperature and time for sterilization in a hot-air oven?
160°C for ≥2 hours or 170°C for 1 hour.
Why is oven sterilization preferred for glassware used with RNA?
It kills organisms and inactivates residual RNA-degrading enzymes (RNases).
Which materials can be autoclaved?
Polypropylene and polycarbonate.
What is filter sterilization used for?
Reagents such as antibiotics, drugs, sugars, amino acids, vitamins, and complex media that are flammable or heat-sensitive.
What is the primary use of laminar flow hoods?
To prevent the spread of viruses and some bacteria in BSL-2 laboratories.
What is a significant advantage of oven sterilization?
It does not cause rusting of steel objects and can be used for heat-stable powders.
What should be done if potential contaminants may pass through a 0.22-μm filter?
Consider autoclaving water before using it for solutions that need to be filter sterilized.
What is the function of a laminar flow unit?
To prevent contamination of reagents and biological cultures by providing clean, ultrafiltered air.
What size of airborne particles can a HEPA filter effectively capture?
Particles larger than 0.3 μm.
What is the primary purpose of aseptic technique in microbiology?
To prevent contamination of cultures, sterile media stocks, and other solutions by unwanted microorganisms.
Why is it important to clean and disinfect lab surfaces?
To prevent contamination before and after use.
What are some basic tools of the microbiologist mentioned in the text?
Agars, inoculating loops, pipettes, broths, and plates.
What are the two major strategies of aseptic work?
Using a Bunsen burner and a laminar flow hood.
What is a common piece of equipment used to create a sterile environment?
Bunsen burner.
